مصطلحات ميكروبيولوجية

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A

• 1. AB Toxins. The structure and activity of many exotoxins are based on the AB model. In this model, the B portion of the toxin is responsible for toxin binding to a cell but does not directly harm it. The A portion enters the cell and disrupts its function.
• 2. Accessory Pigments. Photosynthetic pigments such as carotenoids and phycobiliproteins that aid chlorophyll in trapping light energy.
• 3. Acid Fast. Refers to bacteria like the mycobacteria that cannot be easily decolorized with acid alcohol after being stained with dyes such as basic fuchsin.
• 4. Acid-Fast Staining. A staining procedure that differentiates between bacteria based on their ability to retain a dye when washed with an acid alcohol solution.
• 5. Acidophile.
• 5.محب للحمض Acidophile. كائنات حية دقيقة تكون افضل الشروط لنموها هي في درجة ph بين الصفر و5.5

• 6. Acquired Immune Deficiency Syndrome (AIDS). An infectious disease syndrome caused by the human immunodeficiency virus and is characterized by the loss of a normal immune response, followed by increased susceptibility to opportunistic infections and an increased risk of some cancers.
• 7. Acquired Immune Tolerance. The ability to produce antibodies against nonself antigens while “tolerating” (not producing antibodies against) self-antigens.
• 8. Acquired Immunity. Refers to the type of specific (adaptive) immunity that develops after exposure to a suitable antigen or is produced after antibodies are transferred from one individual to another.
• 9. Actinobacteria. A group of Gram-positive bacteria containing the actinomycetes and their high G + C relatives.
• 10. Actinomycete. An aerobic, Gram-positive bacterium that forms branching filaments (hyphae) and asexual spores.
• 11. Actinorhizae. Associations between actinomycetes and plant roots.
• 12. Activated Sludge. Solid matter or sediment composed of actively growing microorganisms that participate in the aerobic portion of a biological sewage treatment process. The microbes readily use dissolved organic substrates and transform them into additional microbial cells and carbon dioxide.
• 13. Active Immunization. The induction of active immunity by natural exposure to a pathogen or by vaccination.
• 14. Acute Infections. Virus infections with a fairly rapid onset that last for a relatively short time.
• 15. Acute Viral Gastroenteritis. An inflammation of the stomach and intestines, normally caused by Norwalk and Norwalklike viruses, other caliciviruses, rotaviruses, and astroviruses.
• 16. Adenine. A purine derivative, 6-aminopurine, found in nucleosides, nucleotides, coenzymes, and nucleic acids.
• 17. Adenosine Diphosphate (ADP). The nucleoside diphosphate usually formed upon the breakdown of ATP when it provides enregy for work.
• 18. Adenosine 5′-triphosphate (ATP). The triphosphate of the nucleoside adenosine, which is a high energy molecule or has high phosphate group transfer potential and serves as the cell’s major form of energy currency.
• 19. Adhesin. A molecular component on the surface of a microorganism that is involved in adhesion to a substratum or cell. Adhesion to a specific host issue usually is a preliminary stage in pathogenesis, and adhesins are important virulence factors.
• 20. Adjuvant. Material added to an antigen to increase its immunogenicity. Common examples are alum, killed Bordetella pertussis, and an oil emulsion of the antigen, either alone (Freund’s incomplete adjuvant) or with killed mycobacteria (Freund’s complete adjuvant).
• 21. Aerobe. An organism that grows in the presence of atmospheric oxygen.
• 22. Aerobic Anoxygenic Photosynthesis. Photosynthetic process in which electron donors such as organic matter or sulfide, which do not result in oxygen evolution, are used under aerobic conditions.
• 23. Aerobic Respiration. A metabolic process in which molecules, often organic, are oxidized with

oxygen as the final electron acceptor.

• 24. Aerotolerant Anaerobes. Microbes that grow equally well whether or not oxygen is present.
• 25. Aflatoxin. A polyketide secondary fungal metabolite that can cause cancer.
• 26. Agar. A complex sulfated polysaccharide, usually from red algae, that is used as a solidifying

agent in the preparation of culture media.

• 27. Agglutinates. The visible aggregates or clumps formed by an agglutination reaction.
• 28. Agglutination Reaction. The formation of an insoluble immune complex by the cross-linking of

cells or particles.

• 29. Airborne Transmission. The type of infectious organism transmission in which the pathogen is

truly suspended in the air and travels over a meter or more from the source to the host.

• 30. Alkinetes. Specialized, nonmotile, dormant, thick-walled resting cells formed by some

cyanobacteria.

• 31. Alga. A common term for a series of unrelated groups of photosynthetic eucaryotic microorganisms

lacking multicellular sex organs (except for the charophytes) and conducting vessels.

• 32. Algicide. An agent that kills algae.
• * 33. Alkalophile محب للاساس.وهي

كائنات حية دقيقة تنموفي درجة ph بين 8.5 الى 11.5

• 34. Allergen. A substance capable of inducing allergy or specific susceptibility.
• 35. Alpha Hemolysis. A greenish zone of partial clearing around a bacteria colony growing on blood

agar.

• 36. Alpha-proteobacteria. One of the five subgroups of proteobacteria, each with distinctive 16S

r* RNA sequences. This group contains most of the oligotrophic proteobacteria ; some have unusual metabolic modes such as methylotrophy, chemolithotrophy, and nitrogen fixing ability. Many have distinctive morphological features.

• 37. Alveolar Macrophage. A vigorously phagocytic macrophage located on the epithelial surface of

the lung alveoli where it ingests inhaled particulate matter and microorganisms.

• 38. Amensalism. A relationship in which the product of one organism has a negative effect on another

organism.

• 39. Ames Test. A test that uses a special Salmonella strain to test chemicals for mutagenicity and

potential carcinogenicity.

• 40. Amino Acid Activation. The initial stage of protein synthesis in which amino acids are attached

to transfer RNA molecules.

• 41. Aminoglycoside Antibiotics. A group of antibiotics synthesized by Streptomyces and

Micromonospora, which contain a cyclohexane ring and amino sugars; all aminoglycoside antibiotics bind to the small ribosomal subunit and inhibit protein synthesis.

• 42. Amphibolic Pathways. Metabolic pathways that function both catabolically and anabolically.
• 43. Amphitrichous. A cell with a single flagellum at each end.
• 44. Amphotericin B. An antibiotic from a strain of Streptomyces nodosus that is used to treat systemic

fungal infections; it also is used topically to treat candidiasis.

• 45. Anaerobe. كائنات حية دقيقة تنموبمعزل عن الاوكسجين اي هي عضيات (لاهوائية).
• 46. Anaerobic Digestion. The microbiological treatment of sewage wastes under anaerobic conditions

to produce methane.

• 47. Anaerobic Respiration. An erergy-yielding process in which the electron transport chain acceptor

is an inorganic molecule other than oxygen.

• 48. Anammox Process. The coupled use of nitrite as an electron acceptor and ammonium ion as a

donor under anaerobic conditions to yield nitrogen gas.

• 49. Anaphylaxis. An immediate (type I) hypersensitivity reaction following exposure of a sensitized

individual to the appropriate antigen. Mediated by reagin antibodies, chiefly IgE.

• 50. Anthrax. An infectious disease of animals caused by ingesting Bacillus anthracis spores. Can

also occur in humans and is sometimes called woolsorter’s disease.

• 51. صاد حيويAntibiotic.هومنتج للكائنات الحية الدقيقة اومشتقاتها والتي تقتل الكائنات الحية الدقيقة اوتثبط نموه وهي سريعة التاثير .
• 52. Antimetabolite. A compound that blocks metabolic pathways function by competitively inhibiting

a key enzyme’s use of a metabolite because it closely resembles the normal enzyme substrate.

• 53. Antimicrobial Agent.

وهوعامل يقتل الكائنات الحية الدقيقة اويمنع(يثبط) نموها

• 54. Antisepsis. The prevention of infection or sepsis.
• 55. Antiseptic. Chemical agents applied to tissue to prevent infection by killing or inhibiting pathogens.
• 56. Antitoxin. An antibody to a microbial toxin, usually a bacterial exotoxin, that combines specifically

with the toxin, in vivo and in vitro, neutralizing the toxin.

• 57. Apoptosis. Programmed cell death. The fragmentation of a cell into membrane-bound particles

that are eliminated by phagocytosis. Apoptosis is a physiological suicide mechanism that preserves homeostasis and occurs during normal tissue turnover. It causes cell death in pathological circumstances, such as exposure to low concentrations of xenobiotics and infections by HIV and various other viruses.

• 58. Artificially Acquired Active Immunity. The type of immunity that results from immunizing an

animal with a vaccine. The immunized animal now produces its own antibodies and activated lymphocytes.

• 59. Artificially Acquired Passive Immunity. The type of immunity that results from introducing into

an animal antibodies that have been produced either in another animal or by in vitro methods. Immunity is only temporary.

• 60. Ascocarp. A multicellular structure in ascomycetes lined with specialized cells called asci in

which nuclear fusion and meiosis produce ascospores. An ascocarp can be open or closed and may be referred to as a fruiting body.

• 61. Ascogenous Hypha. A specialized hypha that gives rise to one or more asci.
• 62. Ascomycetes. A division of fungi that form ascospores.
• 63. Ascus. A specialized cell, characteristic of the ascomycetes, in which two haploid nuclei fuse to

produce a zygote, which immediately divides by meiosis ; at maturity an ascus will contain ascospores.

• 64. 64. Aspergillosis.

سقم فطري يسببه نوع من فطور Aspergillus

• 65. Atomic Force Microscope. A type of scanning probe microscope that images a surface by moving

a sharp probe over the surface at a constant distance : a very small amount of force is exerted on the tip and probe movement is followed with a laser.

• 66. Attenuation. (1) A mechanism for the regulation of transcription of some bacterial operons by

aminoacyl-tRNAs. (2) A procedure that reduces or abolishes the virulence of a pathogen without altering its immunogenicity.

• 67. Attenuator. A rho-independent termination site in the leader sequence that is involved in attenuation.
• 68. Autoclave. An apparatus for sterilizing objects by the use of steam under pressure. Its development

tremendously stimulated the growth of microbiology.

• 69. Autogenous Infection. An infection that results from a patient’s own microbiota, regardless of

whether the infecting organism became part of the patient’s microbiota subsequent to admission to a clinical care facility.

• 70. Autoimmune Disease. A disease produced by the immune system attacking self-antigens.

Autoimmune disease results from the activation of self-reactive T and B cells that damage tissues after stimulation by genetic or environmental triggers.

• 71. Autoimmunity. Autoimmunity is a condition characterized by the presence of serum autoantibodies

and self-reactive lymphocytes. It may be benign or pathogenic. Autoimmunity is a normal consequence of aging ; is readily inducible by infectious agents, organisms, or drugs ; and is potentially reversible in that it disappears when the offending “agent” is removed or eradicated.

• 72. Autotroph. An organism that uses CO2 as its sole or principal source of carbon.
• 73. Auxotroph. A mutated prototroph that lacks the ability to synthesize an essential nutrient ; and,

therefore, must obtain it or a precursor from its surroundings.

• 74. Axenic. Not contaminated by any foreign organisms ; the term is used in reference to pure microbial

cultures or to germfree animals.

B

• 75. عصياتBacillus

جراثيم على شكل قضيب (rod)

• 76. Bacteremia. The presence of viable bacteria in the blood.
• 77. Bacteria. The domain that contains procaryotic cells with primarily diacyl glycerol diesters in

their membranes and with bacterial rRNA. Bacteria also is a general term for organisms that are composed of procaryotic cells and are not multicellular.

• 78. Bacterial Artificial Chromosome (BAC). A cloning vector constructed from the E. coli F-factor

plasmid that is used to clone foreign DNA fragments in E. coli.

• 79. Bacterial Vaginosis. Bacterial vaginosis is a sexually trasmitted disease caused by Gardnerella

vaginalis, Mobiluncus spp., Mycoplasma hominis, and various anaerobic bacteria. Although a mild disease it is a risk factor for obstetric infections and pelvic inflammatory disease.

• 80. Bactericide. An agent that kills bacteria.
• 81. Bacteriochlorophyll. A modified chlorophyll that serves as the primary light-trapping pigment

in purple and green photosynthetic bacteria.

• 82. Bacteriocin. A protein produced by a bacterial strain that kills other closely related strains.
• 83. Bacteriophage. A virus that uses bacteria as its host ; often called a phage.
• 84. Bacteriophage (phage) Typing. A technique in which strains of bacteria are identified based on

their susceptibility to bacteriophages.

• 85. Bacteriostatic. Inhibiting the growth and reproduction of bacteria.
• 86. Bacteroid. A modified, often pleomorphic, bacterial cell within the root nodule cells of legumes;

after transformation into a symbiosome it carries out nitrogen fixation.

• 87. Baeocytes. Small, spherical, reproductive cells produced by pleurocapsalean cyanobacteria

through multiple fission.

• 88. Balanced Growth. Microbial growth in which all cellular constituents are synthesized at constant

rates relative to eath other.

• 89. Balanitis. Inflammation of the glans penis usually associated with Candida fungi ; a sexually

transmitted disease.

• 90. Barophilic or Barophile. Organisms that prefer or require high pressures for growth and reproduction.
• 91. Barotolerant. Organisms that can grow and reproduce at high pressures but do not require

them.

• 92. Basal Body. The cylindrical structure at the base of procaryotic and eucaryotic flagella that

attaches them to the cell.

• 93. Batch Culture. A culture of microorganisms produced by inoculating a closed culture vessel

containing a single batch of medium.

• 94. B-cell Antigen Receptor (BCR). A transmembrane immunoglobulin complex on the surface of

a B cell that binds an antigen and stimulates the B cell. It is composed of a membrane-bound immunoglobulin, usually IgD or a modified IgM, complexed with another membrane protein (the Ig-α/Ig-β heterodimer).

• 95. Beta Hemolysis. A zone of complete clearing around a bacterial colony growing on blood agar.

The zone does not change significantly in color.

• 96. β-Oxidation Pathway. The major pathway of fatty acid oxidation to produce NADH, FADH2,

and acetyl coenzyme A.

• 97. Beta-proteobacteria. One of the five subgroups of proteobacteria, each with distinctive 16S

rRNA sequences. Members of this subgroup are similar to the alpha-proteobacteria metabolically, but tend to use substances that diffuse from organic matter decomposition in anaerobic zones.

• 98. Binal Symmetry. The symmetry of some virus capsids (e.g., those of complex phages) that is a

combination of icosahedral and helical symmetry.

• 99. Binary Fission. Asexual reproduction in which a cell or an organism separates into two cells.
• 100. Bioaugmentation. Addition of pregrown microbial cultures to an environment to perform a

specific task.

• 101. Biochemical Oxygen Demand (BOD). The amount of oxygen used by organisms in water under

certain standard conditions ; it provides an index of the amount of microbially oxidizable organic matter present.

• 102. Biodegradation. The breakdown of a complex chemical through biological processes that can

result in minor loss of functional groups, fragmentation into larger constituents, or complete breakdown to carbon dioxide and minerals. Often the term refers to the undesired microbialmediated destruction of materials such as paper, paint, and textiles.

• 103. بيوفيلم Biofilms. Organized microbial systems consisting of layers of microbial cells associated with

surfaces, often with complex structural and functional characteristics. Biofilms have physical/ chemical gradients that influence microbial metabolic processes. They can form on inanimate devices (catheters, medical prosthetic devices) and also cause fouling (e.g., of ships’ hulls, water pipes, cooling towers).

• 104. Biogeochemical Cycling. The oxidation and reduction of substances carried out by living

organisms and/or abiotic processes that results in the cycling of elements within and between different parts of the ecosystem (the soil, aquatic environment, and atomshpere).

• 105. Bioinsecticide. A pathogen that is used to kill or disable unwanted insect pests. Bacteria, fungi,

or viruses are used, either directly or after manipulation, to control insect populations.

• 106. Biologic Transmission. A type of vector-borne transmission in which a pathogen goes through

some morphological or physiological change within the vector.

• 107. Bioluminescence. The production of light by living cells, often through the oxidation of molecules

by the enzyme luciferase.

• 108. Biopesticide. The use of a microorganism or another biological agent to control a specific pest.
• 109. Bioremediation. The use of biologically mediated processes to remove or degrade pollutants

from specific environments. Bioremediation can be carried out by modification of the environment to accelerate biological processes, either with or without the addition of specific microorganisms.

• 110. Biosensor. The coupling of a biological process with production of an electrical signal or light to

detect the presence of particular substances.

• 111. Bioterrorism. The intentional or threatened use of viruses, bacteria, fungi, or toxins from living

organisms to produce death or disease in humans, animals, and plants.

• 112. Biotransformation or Microbial Transformation. The use of living organisms to modify substances

that are not normally used for growth.

• 113. Black Peidra. A fungal infection caused by Piedraia hortae that forms hard black nodules on the

hairs of the scalp.

• 114. Blastomycosis. A systemic fungal infection caused by Blastomyces dermatitidis and marked by

suppurating tumors in the skin or by lesions in the lungs.

• 115. Botulism. A form of food poisoning caused by a neurotoxin (botulin) produced by [[Clostridium

botulinum]] serotypes A-G; sometimes found in improperly canned or preserved food.

• 116. Bright-field Microscope. A microscope that illuminates the specimen directly with bright light

and forms a dark image on a brighter background.

• 117. Broad-spectrum Drugs. Chemotherapeutic agents that are effective against many different kinds

of pathogens.

• 118. Budding. A vegetative outgrowth of yeast and some bacteria as a means of asexual reproduction;

the daughter cell is smaller than the parent.

• 119. Bulking Sludge. Sludges produced in sewage treatment that do not settle properly, usually due

to the development of filamentous microorganisms.

• 120. Butanediol Fermentation. A type of fermentation most often found in the family

Enterobacteriaceae in which 2, 3-butanediol is a major product; acetoin is an intermediate in the pathway and may be detected by the Voges-Proskauer test.

C

• 121. Candidiasis. An infection caused by Candida species of dimorphic fungi, commonly involving

the skin.

• 122. Capsule. A layer of well-organized material, not easily washed off, lying outside the bacterial

cell wall.

• 123. Carboxysomes. Polyhedral inclusion bodies that contain the CO2 fixation enzyme ribulose 1, 5-

bisphosphate carboxylase; found in cyanobacteria, nitrifying bacteria, and thiobacilli.

• 124. Carrier. An infected individual who is a potential source of infection for others and plays an

important role in the epidemiology of a disease.

• 125. Caseous Lesion. A lesion resembling cheese or curd; cheesy. Most caseous lesions are caused by M. tuberculosis.
• 126. Casual Carrier. An individual who harbors an infectious organism for only a short period.
• 127. Cathelicidins. Antimicrobial peptides that are produced by skin cells and kill bacterial pathogens. They destroy invaders by either punching holes in their membranes or solubilizing membranes through detergent-like action.
• 128. Cellulitis. A diffuse spreading infection of subcutaneous skin tissue caused by streptococci,

staphylococci, or other organisms. The tissue is inflamed with edema, redness, pain, and interference with function.

• 129. Cell Wall. The strong layer or structure that lies outside the plasma membrane; it supports and

protects the membrane and gives the cell shape.

• 130. Cephalosporin. A group of β-lactam antibiotics derived from the fungus Cephalosporium, which share the 7-aminocephalosporanic acid nucleus.
• 131. Chancroid. A sexually transmitted disease caused by the Gram-negative bacterium Haemophilus ducreyi. Worldwide, chancroid is an important cofactor in the transmission of the AIDS virus.

Also known as genital ulcer disease due to the painful circumscribed ulcers that form on the penis or entrance to the vagina.

• 132. الطلب على الأكسجين الكيميائي (COD). The amount of chemical oxidation required to convert organic matter in water and waste water to CO2.
• 133. Chemolithotropic Autotrophs. Microorganisms that oxidize reduced inorganic compounds to

derive both energy and electrons; CO2 is their carbon source. Also called chemolithoautotrophs.

• 134. Chemoorganotrophic Heterotrophs. Organisms that use organic compounds as sources of energy, hydrogen, electrons, and carbon for biosynthesis.
• 135. Chemostat. A continuous culture apparatus that feeds medium into the culture vessel at the same

rate as medium containing microorganisms is removed; the medium in a chemostat contains one essential nutrient in a limiting quantity.

• 136. Chemotaxis. The pattern of microbial behaviour in which the microorganism moves toward chemical attractants and/or away from repellents.
• 137. Chemotherapeutic Agents. Compounds used in the treatment of disease that destroy pathogens

or inhibit their growth at concentrations low enough to avoid doing undesirable damage to the host.

• 138. Chemotrophs. Organisms that obtain energy from the oxidation of chemical compounds.
• 139. Chickenpox (varicella). A highly contagious skin disease, usually affecting 2- to 7- year-old

children; it is caused by the varicella-zoster virus, which is acquired by droplet inhalation into the respiratory system.

• 140. Chlamydiae. Members of the genus Chlamydia: gram-negative, coccoid cells that reproduce

only within the cytoplasmic vesicles of host cells using a life cycle that alternates between elementary bodies and reticulate bodies.

• 141. Chlamydial Pneumoniaمتدثرة رئوية. A penumonia caused by Chlamydia pneumoniae. Clinically, infections

are mild and 50% of adults have antibodies to the chlamydiae.

• 142. Choleraكوليرا. An acute infectious enteritis, endemic and epidemic in Asia, which periodically spreads

to the Middle East, Africa, Southern Europe, and South America; caused by Vibrio cholerae.

• 143. Choleragen. The cholera toxin; an extremely potent protein molecule elaborated by strains of

Vibrio cholerae in the small intestine after ingestion of feces-contaminated water or food. It acts on epithelial cells to cause hypersecretion of chloride and bicarbonate and an outpouring of large quantities of fluid from the mucosal surface.

• 144. Chromoblastomycosis. A chronic fungal skin infection, producing wartlike nodules that may

ulcerate. It is caused by the black molds Phialophora verrucosa or Fonsecaea pedrosoi.

• 145. Cilia. Threadlike appendages extending from the surface of some protozoa that beat rhythmically

to propel them; cilia are membrane-bound cylinders with a complex internal array of microtubules, usually in aتسعة + 2 pattern.

• 146. Classical Complement Pathway. The antibody-dependent pathway of complement activation;

it leads to the lysis of pathogens and stimulates phagocytosis and other host defenses.

• 147. Classification. The arrangement of organisms into groups based on mutual similarity or evolutionary

relatedness.

• 148. Clone. A group of genetically identical cells or organisms derived by asexual reproduction from

a single parent.

• 149. Coaggregation. The collection of a variety of bacteria on a surface such as a tooth surface

because of cell-to-cell recognition of genetically distinct bacterial types. Many of these interactions appear to be mediated by a lectin on one bacterium that interacts with a complementary carbohydrate receptor on another bacterium.

• 150. Coagulase. An enzyme that induces blood clotting; it is characteristically produced by pathogenic

staphylococci.

• 151. Coccidioidomycosis. A fungal disease caused by Coccidioides immitis that exists in dry, highly alkaline soils. Also known as valley fever, San Joaquin fever, or desert rheumatism.

• 152. Coccus. A roughly spherical bacterial cell.
• 153. Cold Sore. A lesion caused by the herpes simplex virus; usually occurs on the border of the lips

or nares. Also known as a fever blister or herpes labialis.

• 154. Colicin. A plasmid-encoded protein that is produced by enteric bacteria and binds to specific receptors on the cell envelope of sensitive target bacteria, where it may cause lysis or attack specific intracellular sites such as ribosomes.
• 155. Coliform. A Gram-negative, non-sporing, facultative rod that ferments lactose with gas formation within 48 hours at 35°C.
• 156. Colonization. The establishment of a site of microbial reproduction on an inanimate surface or

organism without necessarily resulting in tissue invasion or damage.

• 157. Colony. An assemblage of microorganisms growing on a solid surface such as the surface of an agar culture medium; the assemblage often is directly visible, but also may be seen only microscopically.
• 158. Colony Forming Units (CFU). The number of microorganisms that form colonies when cultured using spread plates or pour plates, an indication of the number of viable microorganisms in a sample.
• 159. Colorless Sulphur Bacteria. A diverse group of non-photosynthetic proteobacteria that can oxidize reduced sulfur compounds such as hydrogen sulfide. Many are lithotrophs and derive energy from sulfur oxidation. Some are unicellular, whereas others are filamentous gliding bacteria.
• 160. Combinatorial Biology. Introduction of genes from one microorganism into another microorganism to synthesize a new product or a modified product, especially in relation to antibiotic synthesis.
• 161. Cometabolism. The modification of a compound not used for growth by a microorganism, which

occurs in the presence of another organic material that serves as a carbon and energy source.

• 162. Commensal. Living on or within another organism without injuring or benefiting the other organism.
• 163. Common Vehicle Transmission. The transmission of a pathogen to a host by means of an inanimate medium or vehicle.
• 164. Communicable Disease. A disease associated with a pathogen that can be transmitted from one host to another.
• 165. Competent. A bacterial cell that can take up free DNA fragments and incorporate them into its genome during transformation.
• 166. Competition. An interaction between two organisms attempting to use the same resource (nutrients, space, etc.).
• 167. Competitive Exclusion Principle. Two competing organisms overlap in resource use, which leads to the exclusion of one of the organisms.
• 168. Complex Medium. Culture medium that contains some ingredients of unknown chemical composition.
• 169. Complex Viruses. Viruses with capsids having a complex symmetry that is neither icosahedral nor helical.
• 170. Composting. The microbial processing of fresh organic matter under moist, aerobic conditions, resulting in the accumulation of a stable humified product, which is suitable for soil improvement and stimulation of plant growth.
• 171. Confocal Scanning Laser Microscope (CSLM). A light microscope in which monochromatic laser-derived light scans across the specimen at a specific level and illuminates one area at a time to form an image. Stray light from other parts of the specimen is blocked out to give an image with excellent contrast and resolution.
• 172. Congenital (neonatal) Herpes. A infection of a newbown caused by transmission of the herpesvirus during vaginal delivery.
• 173. Conjugation. The form of gene transfer and recombination in bacteria that requires direct cellto- cell contact 2. A complex form of sexual reproduction commonly employed by protozoa.
• 174. Conjugative Plasmid. A plasmid that carries the genes for sex pili and can transfer copies of

itself to other bacteria during conjugation.

• 175. Conoid. A hollow cone of spirally coiled filaments in the anterior tip of certain apicomplexan

protozoa.

• 176. Constitutive Mutant. A strain that produces as inducible enzyme continually, regardless of

need, because of a mutation in either the operator or regulator gene.

• 177. Constructed Wetlands. Intentional creation of marshland plant communities and their associated

microorganisms for environmental restoration or to purify water by the removal of bacteria, organic matter, and chemicals as the water passes through the aquatic plant communities.

• 178. Consumer. An organism that feeds directly on living or dead animals, by ingestion or by

phagocytosis.

• 179. Contact Transmission. Transmission of the pathogen by contact of the source or reservoir of the

pathogen with the host.

• 180. Continuous Culture System. A culture system with constant environmental conditions maintained

through continual provision of nutrients and removal of wastes.

• 181. Convalescent Carrier. An individual who has recovered from an infectious disease but continues

to harbor large numbers of the pathogen.

• 182. Cooperation. A positive but not obiligatory interaction between two different organisms. Also

called protocooperation.

• 183. Cortex. The layer of a bacterial endospore that is thought to be particularly important in conferring

heat resistance on the endospore.

• 184. Cryptococcosis. An infection caused by the basidiomycete. Cryptococcus neoformans, which

may involve the skin, lungs, brain, or meninges.

• 185. Cryptosporidiosis. Infection with protozoa of the genus Cryptosporidium. The most common

symptoms are prolonged diarrhea, weight loss, fever, and abdominal pain.

• 186. Cutaneous Diphtheria. A skin disease caused by Corynebacterium diphtheriae that infects

wound or skin lesions, causing a slow-healing ulceration.

• 187. Cyanobacteria. A large group of bacteria that carry out oxygenic photosynthesis using a system

like that present in photosynthetic eucaryotes.

• 188. Cyst. A general term used for a specialized microbial cell enclosed in a wall. Cysts are formed by

protozoa and a few bacteria. They may be dormant, resistant structures formed in response to adverse conditions or reproductive cysts that are a normal stage in the life cycle.

• 189. Cytopathic Effect. The observable change that occurs in cells as a result of viral replication.

Examples include ballooning, binding together, clustering, or ever death of the cultured cells.

• 190. Cytoplasmic Matrix. The protoplasm of a cell that lies within the plasma membrane and outside

any other organelles. In bacteria it is the substance between the cell membrane and the nucleoid.

• 191. Cytotoxin. A toxin or antibody that has a specific toxic action upto cells; cytotoxins are named

according to the cell for which they are specific (e.g., nephrotoxin).

D

• 192. Dane Particle. A 42 nm spherical particle that is one of three that are seen in hepatitis B virus

infections. The Dane particle is the complete virion.

• 193. Dark-Field Microscopy. Microscopy in which the specimen is brightly illuminated while the

background is dark.

• 194. Death Phase. The decrease in viable microorganisms that occurs after the completion of growth in

a batch culture.

• 195. Decimal Reduction Time (D or D value). The time required to kill 90% of the microorganisms

or spores in a sample at a specified temperature.

• 196. Decomposer. An organism that breaks down complex materials into simpler ones, including the

release of simple inorganic products. Often a decomposer such as an insect or earthworm physically reduces the size of substrate particles.

• 197. Defensin. Specific peptides produced by neutrophils that permeabilize the outer and inner membranes

of certain microorganisms, thus killing them.

• 198. Defined Medium. Culture medium made with components of known composition.
• 199. Delta-proteobacteria. One of the five subgroups of proteobacteria. Chemoorganotrophic bacteria

that usually are either predators on other bacteria or anaerobes that generate sulfide from sulfate and sulfite.

• 200. Dendrogram. A treelike diagram that is used to graphically summarize mutual similarities and

relationships between organisms.

• 201. Denitrification. The reduction of nitrate to gaseous products, primarily nitrogen gas, during

anaerobic respiration.

• 202. Dental Plaque. A thin film on the surface of teeth consisting of bacteria embedded in a matrix of

bacterial polysaccharides, salivary glycoproteins, and other substances. 203. Deoxyribonucleic Acid (DNA). The nucleic acid that constitutes the genetic material of all cellular organisms. It is a polynucleotide composed of deoxyribonucleotides connected by phosphodiester bonds. 204. Dermatomycosis. A fungal infection of the skin; the term is a general term that comprises the various forms of tinea, and it is sometimes used to specifically refer to athelete’s foot (tinea pedis). 205. Desert Crust. A crust formed by microbial binding of sand grains in the surface zone of desert soil; crust formation primarily involves cyanobacteria. 206. Detergent. An organic molecule, other than a soap, that serves as a wetting agent and emulsifier; it is normally used as cleanser. But some may be used as antimicrobial agents. 207. Deuteromycetes. In some classification systems, the deuteromycetes or Fungi Imperfecti are a class of fungi. These organisms either lack a sexual stage or it has not yet been discovered. 208. Diauxic Growth. A biphasic growth pattern or response in which a microorganism, when exposed to two nutrients, initially uses one of them for growth and then alters its metabolism to make use of the second.

209. Differential Interference Contrast (DIC) Microscope. A light microscope that employs two beams of plane polarized light. The beams are combined after passing through the specimen and their interference is used to create the image. 210. Differential Media. Culture media that distinguish between groups of microorganisms based on differences in their growth and metabolic products. 211. Differential Staining Procedures. Staining procedures that divide bacteria into separate groups based on staining properties. 212. Diffusely Adhering E. coli (DAEC). DAEC strains of E. coli adhere over the entire surface of epithelial cells and usually cause diarrheal disease in immunologically naive and malnourished children. 213. Dikaryotic Stage. In fungi, having pairs of nuclei within cells or compartments. Each cell contains two separate haploid nuclei, one from each parent. 214. Dinoflagellate. An algal protist characterized by two flagella used in swimming in a spinning pattern. Many are bioluminescent and an important part of marine phytoplankton, some also are important marine pathogens. 215. Diphtheria. An acute, highly contagious childhood disease that generally affects the membranes of the throat and less frequently the nose. It is caused by Corynebacterium diphtheriae. 216. Dipicolinic Acid. A substance present at high concentrations in the bacterial endspore. It is thought to contribute to the endospore’s heat resistance. 217. Diplococcus. A pair of cocci. 218. Directed or Adaptive Mutation. A mutation that seems to be chosen so the organism can better adapt to its surroundings. 219. Disinfectant. An agent, usually chemical, that disinfects; normally, it is employed only with inanimate objects. 220. Disinfection. The killing, inhibition, or removal of microorganisms that may cause disease. It usually refers to the treatment of inanimate objects with chemicals. 221. Disinfection By-products (DBPs). Chlorinated organic compounds such as trihalomethanes formed during chlorine use for water disinfection. Many are carcinogens. 222. Dissimilatory Nitrate Reduction. The process in which some bacteria use nitrate as the electron acceptor at the end of their electron transport chain to produce ATP. The nitrate is reduced to nitrite or nitrogen gas. 223. Dissimilatory Reduction. The use of a substance as an electron acceptor in energy generation. The acceptor (e.g., sulfate or nitrate) is reduced but not incorporated into organic matter during biosynthetic processes. 224. DNA Vaccine. A vaccine that contains DNA which encodes antigenic proteins. It is injected directly into the muscle; the DNA is taken up by the muscle cells and encoded protein antigens are synthesized. This produces both humoral and cell-mediated responses.

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225. Eclipse Period. The initial part of the latent period in which infected host bacteria do not contain any complete virions. 226. Effacing Lesion. The type of lesion caused by enteropathogenic strains of E. coli (EPEC) when the bacteria destroy the brush border of intestinal epithelial cells. The term AE (attaching-effacing) E. coli is now used to designate true EPEC strains that are an important cause of diarrhea in children from developing countries and in traveler’s diarrhoea.

227. Ehrlichiosis. A tick-borne (Dermacentor andersoni, Amblyomma americanum) rickettsial disease caused by Ehrlichia chaffeensis. Once inside leukocytes, a nonspecific illness develops that resembles Rocky Mountain spotted fever. 228. Endogenous Infection. An infection by a member of an individual’s own normal body microbiota. 229. Endosymbiont. An organism that lives within the body of another organism in a symbiotic association. 230. Endosymbiosis. A type of symbiosis in which one organism is found within another organism. 231. Endosymbiotic Theory or Hypothesis. The theory that eucaryotic organelles such as mitochondria and chloroplasts arose when bacteria established an endosymbiotic relationship with the eucaryotic ancestor and then evolved into organelles. 232. Enteric Bacteria (enterobacteria). Members of the family Enterobacteriaceae (Gram-negative, peritrichous or nonmotile, facultatively anaerobic, straight rods with simple nutritional requirements); also used for bacteria that live in the intestinal tract. 233. Enterohemorrhagic E. coli (EHEC). EHEC strains of E. coli (O157:H7) produce several cytotoxins that provoke fluids secretion in traveller’s diarrhea; however, their mode of action is unknown. 234. Enterionvasive E. coli (EIEC). EIEC strains of E. coli cause traveller’s diarrhoea by penetrating and binding to the intestinal epithelial cells, EIEC may also produce a cytotoxin and enterotoxin. 235. Enteropathogenic E. coli (EPEC). EPEC strains of E. coli attach to the brush border of intestinal epithelial cells and cause a specific type of cell damage called effacing lesions that lead to traveller’s diarrhea. 236. Enterotoxigenic E. coli (ETEC). ETEC strains of E. coli produce two plasmid-encoded enterotoxins (which are responsible for traveller’s diarrhea) and the distinguished by their heat stability : heat-stable enterotoxin (ST) and heat-labile enterotoxin (LT). 237. Epidemic (louse-borne) Typhus. A disease caused by Rickettsia prowazekii that is transmitted from person to person by the body louse. 238. Epsilon-proteobacteria. One of the five subgroups of proteobacteria, each with distinctive 16S rRNA sequences. Slender Gram-negative rods, some of which are medically important (Campylobacter and Helicobacter). 239. Ergot. The dried sclerotium of Claviceps purpurea. Also, an ascomycete that parasitizes rye and other higher plants causing the disease called ergotism. 240. Ergotism. The disease or toxic condition caused by eating grain infected with ergot ; it is often accompanied by gangrene, psychotic delusions, nervous spasms, abortion, and convulsions in humans and in animals. 241. Eucarya. The domain that contains organisms composed of eucaryotic cells with primarily glycerol fatty acyl diesters in their membranes and eucaryotic rRNA. 242. Excystation. The escape of one or more cells or organisms from a cyst. 243. Exergonic reaction. A reaction that spontaneously goes to completion as written ; the standard free energy change is negative, and the equilibrium constant is greater than one. 244. Exogenote. The piece of donor DNA that enters a bacterial cell during gene exchange and recombination.

245. Exotoxin. A heat-labile, toxic protein produced by a bacterium as a result of its normal metabolism or because of the acquisition of a plasmid or prophage. It is usually released into the bacterium’s surroundings. 246. Exponential Phase. The phase of the growth curve during which the microbial population is growing at a constant and maximum rate, dividing and doubling at regular intervals. 247. Extracutaneous Sporotrichosis. An infection by the fungus Sporothrix schenckii that spreads throughout the body. 248. Extreme Barophilic Bacteria. Bacteria that require a high-pressure environment to function. 249. Extreme Environment. An environment in which physical factors such as temperature, pH, salinity, and pressure are outside of the normal range for growth of most microorganisms ; these conditions allow unique organisms to survive and function. 250. Extremophiles. Microorganisms that grow under harsh or extreme environmental conditions such as very high temperatures or low pHs. 251. Extrinsic Factor. An environmental factor such as temperature that influences microbial growth in food.

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252. Facultative Anaerobes. Microorganisms that do not require oxygen for growth, but do grow better in its presence. 253. Fecal Coliform. Coliforms whose normal habitat is the intestinal tract and that can grow at 44.5°C. 254. Fecal Enterococci. Enterococci found in the intestine of humans and other warm-blooded animals. They are used as indicators of the fecal pollution of water. 255. Fimbria (fimbriae). A fine, hairlike protein appendage on some gram-negative bacteria that helps attach them to surfaces. 256. Flagellin. The protein used to construct the filament of a bacterial flagellum. 257. Flagellum (flagella). A thin, threadlike appendage on many prokaryotic and eukaryotic cells that is responsible for their motility. 258. Fluorescence Microscope. A microscope that exposes a specimen to light of a specific wavelength and then forms an image from the fluorescent light produced. Usually the specimen is stained with a fluorescent dye or fluorochrome. 259. Fomite (fomites). An object that is not in itself harmful but is able to harbor and transmit pathogenic organisms. Also called fomes. 260. Food-borne Infection. Gastrointestinal illness caused by ingestion of microorganisms, followed by their growth within the host. Symptoms arise from tissue invasion and/or toxin production. 261. Food Web. A network of many interlinked food chains, encompassing primary producers, consumers, decomposers, and detritivores.

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262. Gamma-proteobacteria. One of the five sub-groups of proteobacteria, each with distinctive 16S rRNA sequences. This is the largest subgroup and is very diverse physiologically ; many important genera are facultatively anaerobic chemoorganotrophs. 263. Gas Gangrene. A type of gangrene that arises from dirty, lacerated wounds infected by anaerobic bacteria, especially species of Clostridium. As the bacteria grow, they release toxins and ferment carbohydrates to produce carbon dioxide and hydrogen gas.

264. Gastroenteritis. An acute inflammation of the lining of the stomach and intestines, characterized by anorexia, nausea, diarrhea, abdominal pain, and weakness. It has various causes including food poisoning due to such organisms as E. coli, S. aureus, Campylobacter (campy-lobacteriosis), and Salmonella species ; consumption of irritating food or drink ; or psychological factors such as anger, stress, and fear. Also called enterogastritis. 265. Gas Vacuole. A gas-filled vacuole found in cyanobacteria and some other aquatic bacteria that provides flotation. It is composed of gas vesicles, which are made of protein. 266. Generalized Transduction. The transfer of any part of a bacterial genome when the DNA fragment is packaged within a phage capsid by mistake. 267. General Recombination. Recombination involving a reciprocal exchange of a pair of homologous DNA sequences ; it can occur any place on the chromosome. 268. Generation Time. The time required for a microbial population to double in number. 269. Genetic Engineering. The deliberate modification of an organism’s genetic information by directly changing its nucleic acid genome. 270. Genital Herpes. A sexually transmitted disease caused by the herpes simplex virus type 2. 271. Germicide. An agent that kills pathogens and many nonpathogens but not necessarily bacterial endospores. 272. Giardiasis. A common intestinal disease caused by the parasitic protozoan Giardia lamblia. 273. Glycocalyx. A network of polysaccharides extending from the surface of bacteria and other cells. 274. Gnotobiotic. Animals that are germfree (microorganisms free) or live in association with one or more known microorganisms. 275. Gonococci. Bacteria of the species Neisseria gonorrhoeae—the organism causing gonorrhea. 276. Gonorrhea. An acute infectious sexually transmitted disease of the mucous membranes of the genitourinary tract, eye, rectum, and throat. It is caused by Neisseria gonorrhoeae. 277. Gram Stain. A differential staining procedure that divides bacteria into Gram-positive and Gramnegative groups based on their ability to retain crystal violet when decolorized with an organic solvent such as ethanol. 278. Greenhouse Gases. Gases released from the Earth’s surface through chemical and biological processes that interact with the chemicals in the stratosphere to decrease the release of radiation from the Earth. It is believed that this leads to global warming. 279. Guillain-Barré Syndrome. A relatively rare disease affecting the peripheral nervous system, especially the spinal nerves, but also the cranial nerves. The cause is unknown, but it most often occurs after an influenza infection or flu vaccination. Also called French Polio.

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280. Halophile. A microorganism that requires high levels of sodium chloride for growth. 281. Harborage Transmission. The mode of transmission in which an infectious organism does not undergo morphological or physiological changes within the vector. 282. Healthy Carrier. An individual who harbors a pathogen, but is not ill. 283. Hemolysis. The disruption of red blood cells and release of their hemoglobin. There are several types of hemolysis when bacteria such as streptococci and staphylococci, grow on blood agar. In α-hemolysis, a narrow greenish zone of incomplete hemolysis forms around the colony. A clear zone of complete hemolysis without any obvious colour change is formed during β-hemolysis. 284. Hemolytic Uremic Syndrome. A kidney disease characterized by blood in the urine and often by kidney failure. It is caused by enterohemorrhagic strains of Escherichia coli O157 : H7 that produce a Shiga-like toxin, which attacks the kidneys.

285. Hepatitis A. (formerly infectious hepatitis). A type of hepatitis that is transmitted by fecal - oral contamination ; it primarily affects children and young adults, especially in environments where there is poor sanitation and overcrowding. It is caused by the hepatitis A virus, a singlestranded RNA virus. 286. Hepatitis B. (formely serum hepatitis). This form of hepatitis is caused by a double-stranded DNA virus (HBV) formerly called the “DNA particle”. The virus is transmitted by body fluids. 287. Hepatitis C. About 90% of all cases of viral hepatitis can be traced to either HAV or HBV. The remaining 10% is believed to be caused by one and possibly several other types of viruses. At least one of these is hepatitis C (formerly non-A, non-B). 288. Hepatitis D (formerly delta hepatitis). The liver diseases caused by the hepatitis D virus in those individuals already infected with the hepatitis B virus. 289. Hepatitis E (formerly enteric-transmitted NANB hepatitis). The liver disease caused by the hepatitis E virus. Usually, a subclinical, acute infection results, however, there is a high mortality in women in their last trimester of pregnancy. 290. Heterolactic Fermenters. Microorganisms that ferment sugars to form lactate, and also other products such as ethanol and CO2. 291. Heterotroph. An organism that uses reduced, preformed organic molecules as its principal carbon source. 292. Heterotrophic Nitrification. Nitrification carried out by chemoheterotrophic microorganisms. 293. Hfr strain. A bacterial strain that denotes its genes with high frequency to a recipient cell during conjugation because the F factor is integrated into the bacterial chromosome. 294. High Oxygen Diffusion Environment. A microbial environment in close contact with air and through which oxygen can move at a rapid rate (in comparison wtih the slow diffusion rate of oxygen through water). 295. Holdfast. A structure produced by some bacteria and algae that attaches them to a solid object. 296. Holozoic Nutrition. In this type of nutrition, nutrients (such as bacteria) are acquired by phagocytosis and the subsequent formation of a food vacuole or phagosome. 297. Homolactic Fermenters. Organisms that ferment sugars almost completely to lactic acid. 298. Host. The body of an organism that harbors another organism. It can be viewed as a microenvironment that shelters and supports the growth and multiplication of a parasitic organism. 299. Host Restriction. The degradation of foreign genetic material by nucleases after the genetic material enters a host cell. 300. Human Immunodeficiency Virus (HIV). A lentivirus of the family, Retroviridae that is associated with the onset of AIDS. 301. Hypermutation. A rapid production of multiple mutations in a gene or genes through the activation of special mutator genes. The process may be deliberately used to maximize the possibility of creating desirable mutants. 302. Hyperthermophile. A bacterium that has its growth optimum between 80°C and about 113°C. Hyperthermophiles usually do not grow well below 55°C. 303. Hypha (hyphae). The unit of structure of most fungi and some bacteria ; a tubular filament.

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304. Identification. The process of determining that a particular, isolate or organism belongs to a recognized taxon.

305. Immobilization. The incorporation of a simple, soluble substance into the body of an organism, making it unavailable for use by other organisms. 306. Inclusion Bodies. Granules of organic or inorganic material lying in the cytoplasmic matrix of bacteria. 307. Inclusion Conjunctivitis. An infectitious disease that occurs worldwide. It is caused by Chlamydia trachomatis that infects the eye and causes inflammation and the occurrence of large inclusion bodies. 308. Incubation Period. The period after pathogen entry into a host and before signs and symptoms appear. 309. Incubatory Carrier. An individual who is incubating a pathogen but is not yet ill. 310. Indicator Organism. An organism whose presence indicates the condition of a substance or environment, for example, the potential presence of pathogens. Coliforms are used as indicators of fecal pollution. 311. Infection. The invasion of a host by a microorganism with subsequent establishment and multiplication of the agent. An infection may or may not lead to overt disease. 312. Infection Thread. A tubular structure formed during the infection of a root by nitrogen-fixing bacteria. The bacteria enter the root by way of the infection thread and stimulate the formation of the root nodule. 313. Infectious Disease Cycle (Chain of Infection). The chain or cycle of events that describes how an infectious organism grows, reproduces, and is disseminated. 314. Infectious Dose 50 (ID50). Refers to the dose or number of organisms that will infect 50% of an experimental group of hosts within a specified time period. 315. Infectivity. Infectiousness ; the state or quality of being infectious or communicable. 316. Integration. The incorporation of one DNA segment into a second DNA molecule to form a new hybrid DNA. Integration occurs during such processes as genetic recombination, episome incorporation into host DNA, and prophage insertion into the bacterial chromosome. 317. Integrins. A large family of α/β heterodimers. Integrins are cellular adhesion receptors that mediate cell-cell and cell-substratum interactions. Integrins usually recognize linear amino acid sequences on protein ligands. 318. Integron. A genetic element with an attachment site for site-specific recombination and an integrase gene. It can capture genes and gene cassettes. 319. Intercalating Agents. Molecules that can be inserted between the stacked bases of a DNA double helix, thereby distorting the DNA and including insertion and deletion mutations. 320. Interferon (IFN). A glycoprotein that has nonspecific antiviral activity by stimulating cells to produce antiviral proteins, which inhibit the synthesis of viral RNA and proteins. Interferons also regulate the growth, differentiation, and/or function of a variety of immune system cells. Their production may be stimulated by virus infections, intracellular pathogens (chlamydiae and rickettsias), protozoan parasites, endotoxins, and other agents. 321. Interleukin. A glycoprotein produced by macrophages and T cells that regulates growth and differentiation, particularly of lymphocytes. Interleukins promote cellular and humoral immune responses. 322. Intermediate Filaments. Small protein filaments aboutثمانية toعشرة nm in diameter, in the cytoplasmic matrix of eucaryotic cells that are important in cell structure.

323. Interspecies Hydrogen Transfer. The linkage of hydrogen production from organic matter by anaerobic heterotrophic microorganisms to the use of hydrogen by other anaerobes in the reduction of carbon dioxide to methane. This avoids possible hydrogen toxicity. 324. Intertriginous Candidiasis. A skin infection caused by Candida species. Involves those areas of the body, usually opposed skin surfaces, that are warm and moist (axillae, groin, skin folds). 325. Intoxication. A disease that results from the entrance of a specific toxin into the body of a host. The toxin can induce the disease in the absence of the toxin producing organisms. 326. Intrinsic Factors. Food-related factors such as moisture, pH, and available nutrients that influence microbial growth. 327. Invasiveness. The ability of a microorganism to enter a host, grow and reproduce within the host, and spread throughout its body.

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K

328. Kirby-Bauer Method. A disk diffusion test to determine the susceptibility of a microorganism to chemotherapeutic agents. 329. Koch’s Postulates. A set of rules for proving that microorganism causes a particular disease. 330. Lactic Acid Fermentation. A fermentation that produces lactic acid as the sole or primary product.

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331. Lager. Pertaining to the process of aging beers to allow flavor development. 332. Lag Phase. A period following the introduction of microorganisms into fresh culture medium when there is no increase in cell numbers or mass during batch culture. 333. Latent Period. The initial phase in the one-step growth experiment in which no phages are released. 334. Lectin Complement Pathway. The lectin pathway for complement activation is triggered by the binding of a serum lectin (mannan-binding lectin ; MBL) to mannose-containing proteins or to carbohydrates on viruses or bacteria. 335. Leishmanias. Zooflagellates, members of the genus Leishmania, that cause the disease leishmaniasis. 336. Leishmaniasis. The disease caused by the protozoa called leishmanias. 337. Lepromatous (progressive) Leprosy. A relentless, progressive form of leprosy in which large numbers of Mycobacterium lepae develop in skin cells, killing the skin cells and resulting in the loss of features. Disfiguring nodules from all over the body. 338. Leprosy or Hansen’s Disease. A severe disfiguring skin disease caused by Mycobacterium leprae. 339. Lethal Dose 50 (LD50). Refers to the dose or number of organisms that will kill 50% of an experimental group of hosts within a specified time period. 340. Leukemia. A progressive, malignant disease of blood-forming organs, marked by distorted proliferation and development of leukocytes and their precursors in the blood and bone marrow. Certain leukemias are caused by viruses (HTLV-1, HTLV-2). 341. Leukocidin. A microbial toxin that can damage or kill leukocytes. 342. Lichen. An organism composed of a fungus and either green algae or cyanobacteria in a symbiotic association. 343. Liebig’s Law of the Minimum. Living organisms and populations will grow until lack of a resource begins to limit further growth. 344. Lipopolysaccharide (LPSs). A molecule containing both lipid and polysaccharide, which is important in the outer membrane of the Gram-negative cell wall.

345. Listeriosis. A sporadic disease of animals and humans, particularly those who are immunocompromised or pregnant, caused by the bacterium Listeria monocytogenes. 346. Lithotroph. An organism that uses reduced inorganic compounds as its electron source. 347. Low Oxygen Diffusion Environment. An aquatic environment in which microorganisms are surrounded by deep water layers that limit oxygen-diffusion to the cell surface. In contrast, microorganisms in thin water films have good oxygen transfer from air to the cell surface. 348. LPS-Binding Protein. A special plasma protein that binds bacterial lipopolysaccharides and then attaches to receptors on monocytes, macrophages, and other cells. This triggers the release of IL-1 and other cytokines that stimulate the development of fever and additional endotoxin effects. 349. Lymphogranuloma Venereum (LGV). A sexually transmitted disease caused by Chalmydia trachomatis serotypes L1 – L3, which affect the lymph organs in the genital area. 350. Lysogens. Bacteria that are carrying a viral prophage and can produce bacteriophages under the proper conditions. 351. Lysogeny. The state in which a phage genome remains within the bacterial cell after infection and reproduces along with it rather than taking control of the host and destroying it. 352. Lysosome. A spherical membranous eucaryotic organelle that contains hydrolytic enzymes and is responsible for the intracellular digestion of substances.

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353. Macrolide Antibiotic. An antibiotic containing a macrolide ring, a large lactone ring with multiple keto and hydroxyl groups, linked to one or more sugars. 354. Macromolecule Vaccine. A vaccine made of specific, purified macromolecules derived from pathogenic microorganisms. 355. Macronucleus. The larger of the two nuclei in ciliate protozoa. It is normally popyploid and directs the routine activities of the cell. 356. Macrophage. The name for a large mononuclear phagocytic cell, present in blood, lymph, and other tissues. Macrophages are derived from monocytes. They phagocytose and destroy pathogens ; some macrophages also activate B cells and T cells. 357. Maduromycosis. A subcutaneous fungal infection caused by Madurella mycetoma ; also termed an eumycotic mycetoma. 358. Madurose. The sugar derivative 3-O-methyl-D-galactose, which is characteristic of several actinomycete genera that are collectively called maduromycetes. 359. Magnetosomes. Magnetite particles in magnetotactic bacteria that are tiny magnets and allow the bacteria to orient themselves in magnetic fields. 360. Malaria. A serious infectious illness caused by the parasitic protozoan Plasmodium. Malaria is characterized by bouts of high chills and fever that occur at regular intervals. 361. Mash. The soluble materials released from germinated grains and prepared as a microbial growth medium. 362. Mean Growth Rate Constant (k). The rate of microbial population growth expressed in terms of the number of generations per unit time. 363. Meiosis. The sexual process in which a diploid cell divides and forms two haploid cells. 364. Melting Temperature (Tm). The temperature at which double-standard DNA separates into individual strands ; it is dependent on the G + C content of the DNA and is used to compare genetic material in microbial taxonomy.

365. Membrane Filter Technique. The use of a thin porous filter made from cellulose acetate or some other polymer to collect microorganisms from water, air and food. 366. Meningitis. A condition that refers to inflammation of the brain or spinal cord meninges (membranes). The disease can be divided into bacterial (septic) meningitis and aseptic meningitis syndrome (caused by nonbacterial sources). 367. Mesophile. A microorganism with a growth optimum around 20 to 45°C, a minimum of 15 to 20°C, and a maximum about 45°C or lower. 368. Metachromatic Granules. Granules of polyphosphate in the cytoplasm of some bacteria that appear a different colour when stained with a blue basic dye. They are storage reservoirs for phosphate. Sometimes called volutin granules. 369. Methanogens. Strictly anaerobic archaeons that derive energy by converting CO2, H2, formate, acetate, and other compounds to either methane or methane and CO2. 370. Methylotroph. A bacterium that uses reduced one-carbon compounds such as methane and methanol as its sole source of carbon and energy. 371. Microaerophile. A microorganism that requires low levels of oxygen for growth, around 2 to 10%, but is damaged by normal atmospheric oxygen levels. 372. Microbial Ecology. The study of microorganisms in their natural environments, with a major emphasis on physical conditions, processes, and interactions that occur on the scale of individual microbial cells. 373. Microbial Loop. The mineralization of organic matter synthesized by photosynthetic phytoplankton through the activity of microorganisms such as bacteria and protozoa. This process “loops” minerals and carbon dioxide back for reuse by the primary producers and makes the organic matter unavailable to higher consumers. 374. Microbial Mat. A firm structure of layered microorganisms with complementary physiological activities that can develop on surfaces in aquatic environments. 375. Microbiology. The study of organisms that are usually too small to be seen with the naked eye. Special techniques are required to isolate and grow them. 376. Microbivory. The use of microorganisms as a food source by organisms that can ingest or phagocytose them. 377. Microenvironment. The immediate environment surrounding a microbial cell or other structure, such as a root. 378. Microorganism. An organism that is too small to be seen clearly with the naked eye. 379. Miliary Tuberculosis. An acute form of tuberculosis in which small tubercles are formed in a number of organs of the body because of disemination of M. tuberculosis throughout the body by the bloodstream. Also known as reactivation tuberculosis. 380. Mineralization. The release of inorganic nutrients from organic matter during microbial growth and metabolism. 381. Minimal Inhibitory Concentration (MIC). The lowest concentration of a drug that will prevent the growth of a particular microorganism. 382. Minimal Lethal Concentration (MLC). The lowest concentration of a drug that will kill a particular microorganism.

383. Mitochondrion. The eucaryotic organelle that is the site of electron transport, oxidative phosphorylation, and pathways such as the Krebs cycle ; it provides most of a nonphotosynthetic cell’s energy under aerobic conditions. It is constructed of an outer membrane and an inner membrane, which contains the electron transport chain. 384. Mitosis. A process that takes place in the nucleus of a eucaryotic cell and results in the formation of two new nuclei, each with the same number of chromosomes as the parent. 385. Mixed Acid Fermentation. A type of fermentation carried out by members of the family Enterobacteriaceae in which ethanol and a complex mixture of organic acids are produced. 386. Mixotrophic. Refers to microorganisms that combine autotrophic and heterotrophic metabolic processes (they use inorganic electron sources and organic carbon sources). 387. Modified Atmosphere Packaging (MAP). Addition of gases such as nitrogen and carbon dioxide to packaged foods in order to inhibit the growth of spoilage organisms. 388. Mold. Any of a large group of fungi that cause mold or moldiness and that exist as multicellular filamentous colonies ; also the deposit or growth caused by such fungi. Molds typically do not produce macroscopic fruiting bodies. 389. Most Probable Number (MPN). The statistical estimation of the probable population in a liquid by diluting and determining end points for microbial growth. 390. Mucociliary Blanket. The layer of cilia and mucus that lines certain portions of the respiratory system ; it traps microorganisms up toعشرة μm in diameter and then transports them by ciliary action away from the lungs. 391. Mucociliary Escalator. The mechanism by which respiratory ciliated cells move material and microorganisms, trapped in mucus, out of the pharynx, where it is spit out or swallowed. 392. Multi-drug-resistant Strains of Tuberculosis (MDR-TB). A multi-drug-resistant strain is defined as Mycobacterium tuberculosis resistant to isoniazid and rifampin, with or without resistance to other drugs. 393. Mutation. A permanent, heritable change in the genetic material. 394. Mutualist. An organism associated with another in an obligatory relationship that is beneficial to both. 395. Mycelium. A mass of branching hyphae found in fungi and some bacteria. 396. Mycolic Acids. Complex 60 to 90 carbon fatty acids with a hydroxyl on the β-carbon and an aliphatic chain on the α-carbon, found in the cell walls of mycobacteria. 397. Mycoplasma. Bacteria that are members of the class Mollicutes and order Mycoplasmatales ; they lack cell walls and cannot synthesize peptidoglycan precursors ; most require sterols for growth ; they are the smallest organisms capable of independent reproduction. 398. Mycoplasmal Pneumonia. A type of pneumonia caused by Mycoplasma pneumoniae. Spread involves airborne droplets and close contact. 399. Mycorrhizosphere. The region around ectomycorrhizal mantles and hyphae in which nutrients released from the fungus increase the microbial population and its activities. 400. Mycotoxicology. The study of fungal toxins and their effects on various organisms. 401. Myxobacteria. A group of Gram-negative, aerobic soil bacteria characterized by gliding motility, a complex life cycle with the production of fruiting bodies, and the formation of myxospores.

402. Myxospores. Special dormant spores formed by the myxobacteria.

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403. Narrow-spectrum Drugs. Chemotherapeutic agents that are effective only against a limited variety of microorganisms. 404. Natural Classification. A classification system that arranges organisms into groups whose members share many characteristics and reflect as much as possible the biological nature of organisms. 405. Necrotizing Fasciitis. A disease that results from a severe invasive group. A streptococcus infection. Necrotizing fasciitis is an infection of the subcutanious soft tissues, particularly of fibrous tissue, and is most common on the extremities. It begins with skin reddening, swelling, pain and cellulitis and proceeds to skin breakdown and gangrene after ثلاثة toخمسة days. 406. Negative Staining. A staining procedure in which a dye is used to make the background dark while the specimen is unstained. 407. Neurotoxin. A toxin that is poisonous to or destroys nerve tissue ; especially the toxins secreted by C. tetani, Corynebacterium diphtheriae, and Shigella dysrenteriae. 408. Neustonic. The microorganisms that live at the atmospheric interface of a water body. 409. Neutrophile. Microorgansims that grow best at a neutral pH range between pH 5.5 and 8.0. 410. Niche. The function of an organism in a complex system, including place of the organism, the resources used in a given location, and the time of use. 411. Nitrifying Bacteria. Chemolithotrophic, Gram-negative bacteria that are members of the family Nitrobacteriaceae and convert ammonia to nitrate and nitrite to nitrate. 412. Nitrogen Fixation. The metabolic process in which atmospheric molecular nitrogen is reduced to ammonia ; carried out by cyanobacteria, Rhizobium, and other nitrogen-fixing procaryotes. 413. Nitrogen Oxygen Demand (NOD). The demand for oxygen is sewage treatment, caused by nitrifying microorganisms. 414. Nocardioforms. Bacteria that resemble members of the genus Nocardia ; they develop a substrate mycelium that readily breaks up into rods and coccoid elements (a quality sometimes called fugacity). 415. Nomenclature. The branch of taxonomy concerned with the assignment of names to taxonomic groups in agreement with published rules. 416. Nondiscrete Microorganism. A microorganism, best exemplified by a filamentous fungus, that does not have a defined and predictable cell structure or distinct edges and boundaries. The organism can be defined in terms of the cell structure and its cytoplasmic contents. 417. Normal Microbiota (also indigenous microbial population, microflora, microbial flora). The microorganisms normally associated with a particular tissue or structure. 418. Nucleoid. An irregularly shaped region in the procaryotic cell that contains its genetic material. 419. Nucleolus. The organelle, located within the eucaryotic nucleus and not bounded by a membrane, that is the location of ribosomal RNA synthesis and the assembly of ribosomal subunits. 420. Numerical Aperture. The property of a microscope lens that determines how much light can enter and how great a resolution the lens can provide. 421. Nutrient. A substance that supports growth and reproduction. 422. Nystatin. A polyene antibiotic from Streptomyces noursei that is used in the treatment of Candida infections of the skin, vagina, and alimentary tract.

O

423. O Antigen. A polysaccharide antigen extending from the outer membrane of some gram-negative bacterial cell walls ; it is part of the lipopolysaccharide. 424. Obligate Anaerobes. Microorganisms that cannot tolerate the presence of oxygen and die when exposed to it. 425. One-step Growth Experiment. An experiment used to study the reproduction of lytic phages in which one round of phage reproduction occurs and ends with the lysis of the host bacterial population. 426. Open Reading Frame (ORF). A reading frame sequence not interrupted by a stop codon ; it is usually determined by nucleic acid sequencing studies. 427. Opportunistic Microorganism or Pathogen. A microorganism that is usually free-living or a part of the host’s normal microbiota, but which may become pathogenic under certain circumstances, such as when the immune system is compromised. 428. Opsonization. The action of opsonins in making bacteria and other cells more readily phagocytosed. Antibodies, complement (especially C3b) and fibronectin are potent opsonins. 429. Optical Tweezer. The use of a focused laser beam to drag and isolate a specific microorganism from a complex microbial mixture. 430. Organotrophs. Organisms that use reduced organic compounds as their electron source. 431. Osmophilic Microorganisms. Microorgnisms that grow best in or on media of high solute concentration. 432. Osmotolerant. Organisms that grow over a fairly wide range of water activity or solute concentration. 433. Outer Membrane. A special membrane located outside the peptidoglycan layer in the cell walls of Gram-negative bacteria. 434. Oxidative Burst. The generation of reactive oxygen species, primarily superoxide anion ( – O2 ) and hydrogen peroxide (H2O2) by a plant or an animal, in response to challenge by a potential bacterial, fungal, or viral pathogen. 435. Oxygenic Photosynthesis. Photosynthesis that oxidizes water to form oxygen ; the form of photosynthesis characteristic of algae and cyanobacteria.

P

436. Parasite. An organism that lives on or within another organism (the host) and benefits from the association while harming its host. Often the parasite obtains nutrients from the host. 437. Parasitism. A type of symbiosis in which one organism benefits from the other and the host is usually harmed. 438. Parfocal. A microscope that retains proper focus when the objectives are changed. 439. Pasteur Effect. The decrease in the rate of sugar catobolism and change to aerobic respiration that occurs when microorganisms are switched from anaerobic to aerobic conditions. 440. Pasteurization. The process of heating milk and other liquids to destroy microorgnisms that can cause spoilage or disease. 441. Pathogen. Any virus, bacterium, or other agent that causes disease. 442. Pathogen-Associated Molecular Pattern (PAMP). Conserved molecular structures that occur in patterns on microbial surfaces. The structures and their patterns are unique to particular microorganisms and invariant among members of a given microbial group.

443. Pathogenicity. The condition or quality of being pathogenic, or the ability to cause disease. 444. Pathogenicity Island. A large segment of DNA in some pathogens that contains the genes responsible for virulence ; often it codes for the type III secretion system that allows the pathogen to secrete virulence proteins and damage host cells. A pathogen may have more than one pathogenicity island. 445. Pathogenic Potential. The degree that a pathogen causes morbid signs and symptoms. 446. Ped. A natural soil aggregate, formed partly through bacterial and fungal growth in the soil. 447. Pencillins. A group of antibiotics containing a β-lactam ring, which are active against grampositive bacteria. 448. Peptic Ulcer Disease. A gastritis caused by Helicobacter pylori. 449. Peptidoglycan. A large polymer composed of long chain of alternating N-acetyl-glucosamine and N-acetylmuramic acid residues. The polysaccharide chains are linked to each other through connections between tetrapeptide chains attached to the N-acetylmuramic acids. It provides much of the strength and rigidity possessed by bacterial cell walls. 450. Peptones. Water-soluble digests or hydrolysates of proteins that are used in the preparation of culture media. 451. Period of Infectivity. Refers to the time during which the source of an infectious disease is infectious or is disseminating the pathogen. 452. Periplasmic Space or Periplasm. The space between the plasma membrane and the outer membrane in Gram-negative bacteria, and between the plasma membrane and the cell wall in Gram-positive bacteria. 453. Pertussis. An acute, highly contagious infection of the respiratory tract, most frequently affecting young children, usually caused by Bordetella pertussis or B. parapertussis. Consists of peculiar paroxysms of coughing, ending in a prolonged crowing or whooping respiration ; hence the name whooping cough. 454. Petri Dish. A shallow dish consisting of two round, overlapping halves that is used to grow microorganisms on solid culture medium ; the top is larger than the bottom of the dish to prevent contamination of the culture. 455. Phase-contrast Microscope. A microscope that converts slight differences in refractive index and cell density into easily observed differences in light intensity. 456. Phenetic System. A classification system that groups organisms together based on the similarity of their observable characteristics. 457. Phenol Coefficient Test. A test to measure the effectiveness of disinfectants by comparing their activity against test bacteria with that of phenol. 458. Photolithotrophic Autorophs. Organisms that use light energy, an inorganic electron source (e.g., H2O, H2, H2S) and CO2 as a carbon source. 459. Photoorganotrophic Heterotrophs. Microorganisms that use light energy and organic electron donors, and also employ simple organic molecules rather than CO2 as their carbon source. 460. Phototrophs. Organisms that use light as their energy source. 461. Phycobiliproteins. Photosynthetic pigments that are composed of proteins with attached tetrapyrroles ; they are often found in cyanobacteria and red algae.

462. Phycobilisomes. Special particles on the membranes of cyanobacteria that contain photosynthetic pigments and electron transport chains. 463. Phylogenetic Tree. A graph made of nodes and branches, much like a tree in shape, that shows phylogenetic relationships between groups of organisms and sometimes also indicates the evolutionary development of groups. 464. Phytoplankton. A community of floating photosynthetic organisms, largely composed of algae and cyanobacteria. 465. Phytoremediation. The use of plants and their associated microorganisms to remove, contain, or degrade environmental contaminants. 466. Plankton. Free-floating, mostly microscopic microorganisms that can be found in almost all waters ; a collective name. 467. Plaque. 1. A clear area in a lawn of bacteria or a localized area of cell destruction in a layer of animal cells that results from the lysis of the bacteria by bacteriophages or the destruction of the animal cells by animal viruses, 2. The term also refers to dental plaque, a film of food debris, polysaccharides, and dead cells that cover the teeth. 468. Plasmid Fingerprinting. A technique used to identify microbial isolates as belonging to the same strain because they contain the same number of plasmids with the identical molecular weights and similar phenotypes. 469. Plasmodial (acellular) Slime Mold. A member of the devision Myxomycota that exists as a thin, streaming, multinucleate mass of protoplasm which creeps along in an amoeboid fashion. 470. Plasmodium (pl. plasmodia). A stage in the life cycle of myxomycetes (plasmodial slime molds) ; a multinucleate mass of protoplasm surrounded by a membrane. Also, a parasite of the genus Plasmodium. 471. Plastid. A cytoplasmic orgenelle of algae and higher plants that contains pigments such as chlorophyll, stores food reserves, and often carries out processes such as photosynthesis. 472. Pleomorphic. Refers to bacteria that are variable in shape and lack a single, characteristic form. 473. Poly-β-hydroxybutyrate (PHB). A linear polymer of β-hydroxybutyrate used as a reserve of carbon and energy by many bacteria. 474. Polymerase Chain Reaction (PCR). An in vitro technique used to synthesize large quantities of specific nucleotide sequences from small amounts of DNA. It employs oligonucleotide primers complementary to specific sequences in the target gene and special heat-stable DNA polymerases. 475. Porin Proteins. Proteins that form channels across the outer membrane of Gram-negative bacterial cell walls. Small molecules are transported through these channels. 476. Pour Plate. A petri dish of solid culture medium with isolated microbial colonies growing both on its surface and within the medium, which has been prepared by mixing microorganisms with cooled, still liquid medium and then allowing the medium to harden. 477. Primary (frank) Pathogen. Any organism that causes a disease in the host by direct interaction with or infection of the host. 478. Primary Metabolites. Microbial metabolites produced during the growth phase of an organism. 478. Primary Producer. Photoautotrophic and chemoautotrophic organisms that incorporate carbon dioxide into organic carbon and thus provide new biomass for the ecosystem.

480. Primary Production. The incorporation of carbon dioxide into organic matter by photosynthetic organisms and chemoautotrophic bacteria. 481. Probiotic. A living organism that may provide health benefits beyond its nutritional value when it is ingested. 482. Procaryotic Cells. Cells that lack a true, membrane-enclosed nucleus ; bacteria are procaryotic and have their genetic material located in a nucleoid. 483. Procaryotic Species. A collection of strains that share many stable properties and differ significantly from other groups of strains. 484. Propagated Epidemic. An epidemic that is characterized by a relatively slow and prolonged rise and then a gradual decline in the number of individuals infected. It usually results from the introduction of an infected individual into a susceptible population, and the pathogen is transmitted from person to person. 485. Prostheca. An extension of a bacterial cell, including the plasma membrane and cell wall, that is narrower than the mature cell. 486. Protein Engineering. The rational design of proteins by constructing specific amino acid sequences through molecular techniques, with the objective of modifying protein characteristics. 487. Proteobacteria. A large group of bacteria, primarily Gram-negative, that 16S rRNA sequence comparisons show to be phylogenetically related ; proteobacteria contain the purple photosynthetic bacteria and their relatives and are composed of the α, β, γ, δ and ε subgroups. 488. Proteome. The complete collection of proteins that an organism produces. 489. Protists. Eucaryotes with unicellular organization, either in the form of solitary cells or colonies of cells lacking true tissues. 490. Protoplast. A bacterial or fungal cell with its cell wall completely removed. It is spherical in shape and osmotically sensitive. 491. Protoplast Fusion. The joining of cells that have had their walls weakened or completely removed. 492. Prototroph. A microorganism that requires the same nutrients as the majority of naturally occurring members of its species. 493. Protozoan or Protozoon (pl. Protozoa). A microorganism belonging to the Protozoa subkingdom. A unicellular or acellular eucaryotic protist whose organelles have the functional role of organs and tissues in more complex forms. Protozoa vary greatly in size, morphology, nutrition, and life cycle. 494. Protozoology. The study of protozoa. 495. Pseudopodium or Pseudopod. A nonpermanent cytoplasmic extension of the cell body by which amoebae and amoeboid organisms move and feed. 496. Psittacosis (ornithosis). A disease due to a strain of Chlamydia psittaci, first seen in parrots and later found in other birds and domestic fowl (in which it is called ornithosis). It is transmissible to humans. 497. Psychrophile. A microorganisms that grows well at 0°C and has an optimum growth temperature of 15°C or lower and a temperature maximum around 20°C.

498. Psychrotroph. A microorganism that grows at 0°C, but has a growth optimum between 20 and 30°C, and a maximum of about 35°C. 499. Puerperal Fever. An acute, febrile condition following childbirth ; it is characterized by infection of the uterus and/or adjacent regions and is caused by streptococci. 500. Pulmonary Anthrax. A form of anthrax involving the lungs. Also known as woolsorter’s disease. 501. Pure Culture. A population of cells that are identical because they arise from a single cell. 502. Putrefaction. The microbial decomposition of organic matter, especially the anaerobic breakdown of proteins, with the production of foul-smelling compounds such as hydrogen sulfide and amines.

Q

503. Quellung Reaction. The increase in visibility or the swelling of the capsule of a microorganism in the presence of anitbodies against capsular antigens. 504. Quorum Sensing. The process in which bacteria monitor their own population density by sensing the levels of signal molecules that are released by the microorganisms. When these signal molecules reach a threshold concentration, quorum-dependent genes are expressed.

R

505. Rabies. An acute infectious disease of the central nervous system, which affects all warmblooded animals (including humans). It is caused by an ssRNA virus belonging to the genus Lyssavirus in the family Rhabdoviridae. 506. Radappertization. The use of gamma rays from a cobalt source for control of microorganisms in foods. 507. Radioimmunoassay (RIA). A very sensitive assay technique that uses a purified radioisotopelabeled antigen or antibody to compete for antibody or antigen with unlabeled standard and samples to determine the concentration of a substance in the samples. 508. Recombinant DNA Technology. The techniques used in carrying out genetic engineering ; they involve the identification and isolation of a specific gene, the insertion of the gene into a vector such as a plasmid to form a recombinant molecule, and the production of large quantities of the gene and its products. 509. Recombinant-vector Vaccine. The type of vaccine that is produced by the introduction of one or more of a pathogen’s genes into attenuated viruses or bacteria. The attenuated virus or bacterium serves as a vector, replicating within the vertebrate host and expressing the gene(s) of the pathogen. The pathogen’s antigens induce an immune response. 510. Recombination. The process in which a new recombinant chromosome is formed by combining genetic material from two organisms. 511. Red Tides. Red tides occur frequently in coastal areas and often are associated with population blooms of dinoflagellates. Dinoflagellate pigments are responsible for the red colour of the water. Under these conditions, the dinoflagellates often produce saxitoxin, which can lead to paralytic shellfish poisoning. 512. Reductive Dehalogenation. The cleavage of carbon-halogen bonds by anaerobic bacteria that creates a strong electron-donating environment. 513. Regulatory Mutants. Mutant organisms that have lost the ability to limit synthesis of a product, which normally occurs by regulation of activity of an earlier step in the biosynthetic pathway. 514. Reservoir. A site, alternate host, or carrier that normally harbors pathogenic organisms and serves as a source from which other individuals can be infected.

515. Reservoir Host. An organism other than a human that is infected with a pathogen that can also infect humans. 516. Residuesphere. The region surrounding organic matter such as a seed or plant part in which microbial growth is stimulated by increased organic matter availability. 517. Resolution. The ability of a microscope to separate or distinguish between small objects that are close together. 518. Restricted Transduction. A transduction process in which only a specific set of bacterial genes are carried to another bacterium by a temperate phage ; the bacterial genes are acquired because of a mistake in the excision of a prophage during the lysogenic life cycle. 519. Retroviruses. A group of viruses with RNA genomes that carry the enzyme reverse transcriptase and form a DNA copy of their genome during their reproductive cycle. 520. Ribotyping. Ribotyping is the use of E.coli rRNA to probe chromosomal DNA in Southern blots for typing bacterial strains. This method is based on the fact that rRNA genes are scattered throughout the chromosome of most bacteria and therefore polymorphic restriction endonuclease patterns result when chromosomes are digested and probed with rRNA. 521. Rocky Mountain Spotted Fever. A disease caused by Rickettsia rickettsii. 522. Root Nodule. Gall-like structures on roots that contain endosymbiotic nitrogen-fixing bacteria (e.g., Rhizobium or Bradyrhizobium is present in legume nodules).

S

• 523. Run. The straight line movement of a bacterium.

• 524. Salmonellosis.

سقم يحدثه نوع محدد من السلمونيلا يحدث عادة نتيجة ابتلاع الطعام الذي يحوي السلمونيلا اواحدى مشتقاتها ويعهد ايضا بالالتهاب المعدي المعوي للسلمونيلا اوتسمم الغذاء بالسلمونيلا

• 525. Sanitization. Reduction of the microbial population on an inanimate object to levels judged safe

by public health standards ; usually, the object is cleaned.

• 526. Saprophyte. An organism that takes up nonliving organic nutrients in dissolved form and usually

grows on decomposing organic matter.

• 527. Saprozoic Nutrition. Having the type of nutrition in which organic nutrients are taken up in

dissolved form ; normally refers to animals or animal-like organisms.

• 528. Scanning Electron Microscope (SEM). An electron microscope that scans a beam of electrons

over the surface of a specimen and forms an image of the surface from the electrons that are emitted by it.

• 529. Scanning Probe Microscope. A microscope used to study surface features by moving a sharp

probe over the object’s surface (e.g., the Scanning Tunneling Microscope).

• 530. Secondary Metabolites. Products of metabolism that are synthesized after growth has been

completed.

• 531. Secondary Treatment. The biological degradation of dissolved organic matter in the process of

sewage treatment ; the organic material is either mineralized or changed to settleable solids.

• 533. Selective Media. Culture media that favor the growth of specific microorganisms ; this may be

accomplished by inhibiting the growth of undesired microorganisms.

• 533. Selective Toxicity. سمية انتقائية:

قدرة عناصر العلاجية الكيميائية على اغتال اوتثبيط امراضية العضيات الدقيقة بينما تكون الاضرار على المضيف(الشخص المصاب) اقل مايمكن .

• 534. Sepsis. Systemic response to infection. The systemic response is manifested by two or more of

the following conditions as a result of infection : temperature > 38 or < 36 °C ; heart rate > 90 beats per min ; respiratory rate > 20 breaths per min, or pCO2 < 32 mm Hg ; leukocyte count > 12,000 cells per ml3 or > 10% immature (band) forms. Sepsis also has been defined as the presence of pathogens or their toxins in blood and other tissues.

• 535. Septicemia. A disease associated with the presence in the blood of pathogens or bacterial toxins.

• 536. Septic Shock. Sepsis associated with severe hypotension despite adequate fluid resuscitation,

along with the presence of perfusion abnormalities that may include, but are not limited to, lactic acidosis, oliguria, or an acute alternation in mental status. Gram-positive bacteria, fungi, and endotoxin-containing Gram-negative bacteria can initiate the pathogenic cascade of sepsis leading to septic shock.

• 537. Septum. A partition or crosswall that occurs between two cells in a bacterial (e.g. actinomycete

or fungal filament, or which partitions off fungal structures such as spores. Septa also divide parent cells into two daughter cells during bacterial binary fission.

• 538. Serotyping. A technique or serological procedure that is used to differentiate between strains

(serovars or serotypes) of microorganisms that have differences in the antigenic composition of a structure or product.

• 539. Serum (pl. Serums or Sera). The clear, fluid portion of blood lacking both blood cells and

fibrinogen. It is the fluid remaining after coagulation of plasma, the noncellular liquid faction of blood.

• 540. Serum Resistance. The type of resistance that occurs with bacteria such as Neisseria gonorrhoeae

because the pathogen interferes with membrane attack complex formation during the complement cascade.

• 541. Settling Basin. A basin used during water purification to chemically precipitate out fine

particles, microorganisms, and organic material by coagulation or flocculation.

• 542. Sex Pilus. A thin protein appendage required for bacterial mating or conjugation. The cell with

sex pili donates DNA to recipient cells.

• 543. Sheath. A hollow tubelike structure surroundings a chain of cells and present in several genera

of bacteria.

• 544. Shigellosis. The diarrheal disease that arises from an infection with Shigella spp. Often called

bacillary dysentery.

• 545. Shine-Dalgarno Sequence. A segment in the leader of procaryotic mRNA that binds to a special

sequence on the 16S rRNA of the small ribosomal subunit. This helps properly orient the mRNA on the ribosome.

• 546. Shingles (Herpes Zoster). A reactivated form of chickenpox caused by the varicella-zoster

virus.

• 547. Signal Peptide. The special amino-terminal sequence on a peptide destined for transport that

delays protein folding and is recognized in bacteria by the Sec-dependent pathway machinery.

• 548. Silent Mutation. A mutation that does not result in a change in the organism’s proteins or phenotype

even though the DNA base sequence has been changed.

• 549. Simple Matching Coefficient (SSM). An association coefficient used in numerical taxonomy ;

the proportion of characters that match regardless of whether or not the attribute is present.

• 550. Site-specific Recombination. Recombination of nonhomologous genetic material with a

chromosome at a specific site.

• 551. S-layer. A regularly structure layer composed of protein or glycoprotein that lies on the surface

of many bacteria. It may protect the bacterium and help give it shape and rigidity.

• 552. Slime. The viscous extracellular glycoproteins or glycolipids produced by staphylococci and

Pseudomonas aeruginosa bacteria that allows them to adhere to smooth surfaces such as prosthetic medical devices and catheters. More generally, ther term often refers to an easily removed, diffuse, unorganized layer of extracellular material that surrounds a bacterial cell.

• 553. Slime Layer. A layer of diffuse, unorganized, easily removed material lying outside the bacterial

cell wall.

• 554. Slow Sand Filter. A bed of sand through which water slowly flows ; the gelatinous microbial

layer on the sand grain surface removes waterborne microorganisms, particularly Giardia, by adhesion to the gel. This type of filter is used in some water purification plants.

• 555. Sorocarp. The fruiting structure of the Acrasiomycetes.

• 556. Sorus. A type of fruiting structure composed of a mass of spores or sporangia.

• 557. Source. The location or object from which a pathogen is immediately transmitted to the host,

either directly or through an intermediate agent.

• 558. Species. Species of higher organisms are groups of interbreeding or potentially interbreeding

natural populations that are reproductively isolated. Bacterial species are collections of strains that have many stable properties in common and differ significantly from other groups of strains.

• 559. Spheroplast. A relatively spherical cell formed by the weakening or partial removal of the rigid

cell wall component (e.g., by pencillin treatment of Gram-negative bacteria). Spheroplasts are usually osmotically sensitive.

• 560. Spirillum. A rigid, spiral-shaped bacterium.

• 561. Spirochete. A flexible, spiral-shaped bacterium with periplasmic flagella.

• 562. Spore. A differentiated, specialized form that can be used for dissemination, for survival of

adverse conditions because of its heat and dessication resistance, and/or for reproduction. Spores are usually unicellular and may develop into vegetative organisms or gametes. They may be produced asexually or sexually and are of many types.

• 563. Sporulation. The process of spore formation.

• 564. Spread Plate. A petri dish of solid culture medium with isolated microbial colonies growing on

its surface, which has been prepared by spreading a dilute microbial suspension evenly over the agar surface.

• 565. Stalk. A nonliving bacterial appendage produced by the cell and extending from it.

• 566. Staphylococcal Food Poisoning. A type of food poisoning caused by ingestion of improperly

stored or cooked food in which Staphylococcus aureus has grown. The bacteria produce exotoxins that accumulate in the food.

• 567. Staphylococcal Scalded Skin Syndrome (SSSS). A disease caused by staphylococci that produce

an exfoliative toxin. The skin becomes red (erythema) and sheets of epidermic may separate from the underlying tissue.

• 568. Starter Culture. An inoculum, consisting of a mixture of carefull selected microorganisms,

used to start a commercial fermentation.

• 569. Stationary Phase. The phase of microbial growth in a batch culture when population growth

ceases and the growth curve levels off.

• 570. Stem-nodulating Rhizobia. Rhizobia (members of the genera Rhizobium, Bradyrhizobium, and

Azorhizobium) that produce nitrogen-fixing structures above the soil surface on plant stems. These most often are observed in tropical plants and produced by Azorhizobium.

• 571. Sterilization. The process by which all living cells, viable spores, viruses, and viroids are

either destroyed or removed from an objector habitat.

• 572. Strain. A population of organisms that descends from a single organism or pure culture isolate.

• 573. Streak Plate. A petri dish of solid culture medium with isolated microbial colonies growing on

its surface, which has been prepared by spreading a microbial mixture over the agar surface, using an inoculating loop.

• 574. Streptococcal Pneumonia. A endogenous infection of the lungs caused by Streptococcus

pneumoniae that occurs in predisposed individuals.

• 575. Streptococcal Sore Throat. One of the most common bacterial infections of humans. It is commonly

referred to as “strep throat”. The disease is spread by droplets of saliva or nasal secretions and is caused by Streptococcus spp. (particularly group A streptococci).

• 576. Streptolysin-O (SLO). A specific hemolysin produced by Streptococcus pyogenes that is inactivated

by oxygen (hence the “O” in its name). SLO casuses beta-hemolysis of blood cells on agar plates incubated anaerobically.

• 577. Streptolysin-S (SLS).

هومادة تنتجها المكورات العقدية المقيحة وتكون هذه المادة مرتبطة بجدار الخلية الجرثومية ولكنها يمكن في بعض الحالات ان تحرر . وهذه المادة تسبب انحلالا للدم من النمط بيتا على وسط اغار بالدم ويمكن ان تعمل كقاتل للكريات الدم البيضاء بقتل خلايا الدم البيضاءالتي تقوم ببلعمة الخلايا الجرثومية التي ترتبط بها

A product of Streptococcus pyogenes that is bound to the bacterial cell

but may sometimes be released. SLS causes beta hemolysis on aerobically incubated blood-agar plates and can act as a leukocidin by killing leukocytes that phogocytose the bacterial cell to which it is bound.

• 578. Stromatolite. Dome-like microbial mat communities consisting of filamentous photosynthetic

bacteria and occluded sediments (often calcareous or siliceous). They usually have a laminar structure. Many are fossilized, but some modern forms occur.

• 579. Superinfection.

عدوى فطرية اوجرثومية جديدة للسقمى والتي تكون مقاومة للادوية التي استخدمت للمعالجة

• 580. Swab. مسحة(قطنية)

حشوة من مادة ممتصة (لها قدرة امتصاصية) عادة تكون ملفوفة على نهاية عود صغير (غالباقد يكون خشبيا) ويستخدم لتطبيقات طبية :مثل اخذ عينات لاماكن محددة لفحص الجراثيم فيها.اولازالة المواد من منطقة معينة also, a dacron-tipped polystyrene applicator.

• 581. Symbiosis. The living together or close association of two dissimilar organisms, each of these

organisms being known as a symbiont.

• 582. Syntrophism. The association in which the growth of one organism either depends on, or is

improved by, the provision of one or more growth factors or nutrients by a neighboring organism. Sometimes both organisms benefit.

• 583. Systematic Epidemiology. The field of epidemiology that focuses on the ecological and social

factors that influence the development of emerging and reemerging infectious disease.

• 584. Systematics.

دراسة فهمية للكائنات الحية الهدف النهائي لها هوتنظيمها وتمييز صفاتها في اسلوب منظم ويمكن اعتبارها مرادفا لفهم تصنيف الانواع

• 585. Taxon. A group into which related organisms are classified.

T

586. Taxonomy. The science of biological classification; it consists of three parts : classification, nomenclature and identification. 587. T Cell or T Lymphocyte. A type of lymphocyte derived from bone marrow stem cells that matures into an immunologically competent cell under the influence of the thymus. T cells are involved in a variety of cell-mediated immune reactions. 588. T-Cell Antigen Receptor (TCR). The receptor on the T cell surface consisting of two antigenbinding peptide chains ; it is associated with a large number of other glycoproteins. Binding of antigen to the TCR, usually in association with MHC, activates the T cell. 589. Teichoic Acids. Polymers of glycerol or ribitol joined by phosphates ; they are found in the cell walls of Gram-positive bacteria. 590. Temperate Phages. Bacteriophages that can infect bacteria and establish a lysogenic relationship rather than immediately lysing their hosts. 591. Tetanolysin. A hemolysin that aids in tissue destruction and is produced by Clostridium tetani. 592. Tetrapartite Associations. A symbiotic association of the same plant with three different types of microorganisms. 593. Theory. A set of principles and concepts that have survived rigorous testing and that provide a systematic account of some aspects of nature. 594. Thermal Death Time (TDT). The shortest period of time needed to kill all the organisms in a microbial population at a specified temperature and under defined conditions. 595. Thermoacidophiles. A group of bacteria that grow best at acid pHs and high temperatures ; they are members of the Archaea. 596. Thermophile. A microorganism that can grow at temperatures of 55°C or higher ; the minimum is usually around 45°C. 597. Thrush. Infection of the oral mucous membrane by the fungus Candila albicans ; also known as oral candidiasis. 598. Toxigenicity. The capacity of an organism to produce a toxin. 599. Toxin. A microbial product or component that injures another cell or organism. Often the term refers to a poisonous protein, but toxins may be lipids and other substances. 600. Transformation. A mode of gene transfer in bacteria in which a piece of free DNA is taken up by a bacterial cell and integrated into the recipient genome. 601. Transgenic Animal or Plant. An animal or plant that has gained new genetic information from the insertion of foreign DNA. It may be produced by such techniques as injecting DNA into animal eggs, electroporation of mammalian cells and plant cell protoplasts, or shooting DNA into plants cells with a gene gun. 602. Transmission Electron Microscope (TEM). A microscope in which an image is formed by passing an electron beam through a specimen and focusing the scattered electrons with magnetic lenses. 603. Transovarian Passage. The passage of a microorganisms such as a rickettsia from generation to generation of hosts through tick eggs. (No humans or other mammals are needed as reservoirs for continued propagation.) 604. Traveller’s Diarrhoea. A type of diarrhoea resulting from ingestion of viruses, bacteria, or protozoa normally absent from the traveller’s environment. A major pathogen is enterotoxigenic Escherichia coli.

605. Trichomoniasis. A sexually transmitted disease caused by the parasitic protozoan Trichomonas vaginalis. 606. Tripartite Associations. A symbiotic association of the same plant with two types of microorganisms. 607. Trophozoite. The active, motile feeding stage of a protozoan organism ; in the malarial parasite, the stage of schizogony between the ring stage and the schizont. 608. Tropism. The movement of living organisms toward or away from a focus of heat, light, or other stimulus. 609. Tubercle. A small, rounded nodular lesion produced by Mycobacterium tuberculosis. 610. Tuberculoid (neural) Leprosy. A mild, nonprogressive form of leprosy that is associated with delayed-type hypersensitivity to antigens on the surface of Mycobacterium leprae. It is characterized by early nerve damage and regions of the skin that have lost sensation and are surrounded by a border of nodules. 611. Tuberculosis (TB). An infectious disease of humans and other animals resulting from an infection by a species of Mycobacterium and characterized by the formation of tubercles and tissue necrosis, primarily as a result of host hypersensitivity and inflammation. Infection is usually by inhalation, and the disease commonly affects the lungs (pulmonary tuberculosis), although it may occur in any part of the body. 612. Tularemia. A plaguelike disease of animals caused by the bacterium Francisella tularensis subsp. tularensis (Jellison type A), which may be transmitted to humans. 613. Tumble. Random turning or tumbling movements made by bacteria when they stop moving in a striaght line. 614. Turbidostat. A continuous culture system equipped with a photocell that adjusts the flow of medium through the culture vessel so as to maintain a constant cell density or turbidity.

U

615. Ultramicrobacteria. Bacteria that can exist normally in a miniaturized form or which are capable of miniaturization under low-nutrient conditions. They may be 0.2 μm or smaller in diameter. 616. Ultraviolet (UV) Radiation. Radiation of fairly short wavelength, aboutعشرة to 400 nm, and high energy.

V

617. Vector-borne Transmission. The transmission of an infectious pathogen between hosts by means of a vector. 618. Vehicle. An inanimate substance or medium that transmits a pathogen. 619. Vibrio. A rod-shaped bacterial cell that is curved to form a comma or an incomplete spiral. 620. Virology. The branch of microbiology that is concerned with viruses and viral diseases. 621. Virulence. The degree or intensity of pathogenicity of an organism as indicated by case fatality rates and/or ability to invade host tissues and cause disease. 622. Virulence Factor. A bacterial product, usually a protein or carbohydrate, that contributes to virulence or pathogenicity. 623. Virus. An infectious agent having a simple acellular oganization with a protein coat and a single type of nucleic acid, lacking independent metabolism and reproducing only within living host cells.

624. Vitamin. An organic compound required by organisms in minute quantities for growth and reproduction because it cannot be synthesized by the organism ; vitamins often serve as enzyme cofactors or parts of cofactors.

W

625. Whole-genome Shotgun Sequencing. An approach to genome sequencing in which the complete genome is broken into random fragments, which are then individually sequenced. Finallly the fragments are placed in the proper order using sophisticated computer programs. 626. Whole-organism Vaccine. A vaccine made from complete pathogens, which can be of four types : inactivated viruses ; attenuated viruses ; killed microorganisms ; and live, attenuated microbes. 627. Widal Test. A test involving agglutination of typhoid bacilli when they are mixed with serum containing typhoid antibodies from an individual having typhoid fever ; used to detect the presence of Salmonella typhi and S. paratyphi. 628. Winogradsky Column. A glass column with an anaerobic lower zone and an aerobic upper zone, which allows growth of microorganisms under conditions similar to those found in a nutrient- rich lake.

X

• 629. Xenograft. A tissue graft between animals of different species.
• 630. Xerophilic Microorganisms. Microorganisms that grow best under low aw conditions, and may

not be able to grow at high aw values.

Y

• 631. Yellow Fever. An acute infectious disease caused by a flavivirus, which is transmitted to humans

by mosquitoes. The liver is affected and the skin turns yellow in this disease.

• 632. YM Shift. The change in shape by dimorphic fungi when they shift from the yeast (Y) form in the animal body to the mold or mycelial form (M) in the environment