| gametangium (gam-ùe-tan_je-um; pl., gametangia) | A structure that contains gametes or in which gametes are formed.
(See 557)
|
 |
|
|
| gamma-proteobacteria | One of the five subgroups 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.
(See 498)
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|
|
| gas gangrene (gang_grøen) | 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.
(See 915)
|
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|
|
| gastritis (gas-tri_tis) | Inflammation of the stomach.
(See 918)
|
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|
|
| gastroenteritis (gas_tro-en-ter-i_tis) | 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 (campylobacteriosis), and Salmonella species; consumption of irritating food or drink; or psychological factors such as anger, stress, and fear. Also called enterogastritis.
(See 929)
|
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| 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.
(See 51)
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|
| gene (jøen) | A DNA segment or sequence that codes for a polypeptide, rRNA, or tRNA.
(See 241)
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|
| gene gun | A device that uses high-pressure gas or another propellant to shoot a spray of DNA-coated microprojectiles into cells and transform them. Sometimes it is called a biolistic device.
(See 335)
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|
|
| generalized transduction | The transfer of any part of a bacterial genome when the DNA fragment is packaged within a phage capsid by mistake.
(See 308)
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|
|
| general recombination | Recombination involving a reciprocal exchange of a pair of homologous DNA sequences; it can occur any place on the chromosome.
(See 292)
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|
| generation time | The time required for a microbial population to double in number.
(See 115)
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|
| genetic engineering | The deliberate modification of an organism's genetic information by directly changing its nucleic acid genome.
(See 320)
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|
| genital herpes (her_pøez) | A sexually transmitted disease caused by the herpes simplex virus type 2.
(See 885)
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|
| genital ulcer disease | See chancroid.
(See 914)
|
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|
|
| genome (je_nøom) | The full set of genes present in a cell or virus; all the genetic material in an organism; a haploid set of genes in a cell.
(See 228)
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|
|
| genomics | The study of the molecular organization of genomes, their information content, and the gene products they encode.
(See 345)
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| genus (je_n@s) | A well-defined group of one or more species that is clearly separate from other genera.
(See 426)
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|
| geographic information system (GIS) | A data management system that organizes and displays digital map data from remote sensing and aids in the analysis of relationships between mapped features.
(See 850)
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|
| German measles | See rubella.
(See 875)
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|
|
| germicide (jer_mùõ-søõd) | An agent that kills pathogens and many nonpathogens but not necessarily bacterial endospores.
(See 138)
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|
|
| germination (jer²mùõ-na_shun) | The stage following bacterial endospore activation in which the endospore breaks its dormant state. Germination is followed by outgrowth.
(See 71)
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|
| Ghon complex (gon) | The initial focus of parenchymal infection in primary pulmonary tuberculosis.
(See 908)
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|
| giardiasis (je²ar-di_ah-sis) | A common intestinal disease caused by the parasitic protozoan Giardia lamblia.
(See 953)
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|
| gingivitis (jin-jùõ-vi_tis) | Inflammation of the gingival tissue.
(See 936)
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|
|
| gingivostomatitis (jin²jùõ-vo-sto²m@-ti_tis) | Inflammation of the gingiva and other oral mucous membranes.
(See 884)
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|
|
| gliding motility | A type of motility in which a microbial cell glides along when in contact with a solid surface.
(See 66, 482)
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| global regulatory systems | Regulatory systems that simultaneously affect many genes and pathways.
(See 281)
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|
|
| glomerulonephritis (glo-mer²u-lo-nùe-fri_tis) | An inflammatory disease of the renal glomeruli.
(See 905)
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|
| glucans | Polysaccharides composed of glucose units held together by glycosidic linkages. Some types of glucans have a(1_3) and a(1_6) linkages and bind bacterial cells together on teeth forming a plaque ecosystem.
(See 936)
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|
|
| gluconeogenesis (gloo_ko-ne_o-jen_e-sis) | The synthesis of glucose from noncarbohydrate precursors such as lactate and amino acids.
(See 209)
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|
| glycocalyx (gli_ko-kal_iks) | A network of polysaccharides extending from the surface of bacteria and other cells.
(See 61)
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|
| glycogen (gli_ko-jen) | A highly branched polysaccharide containing glucose, which is used to store carbon and energy.
(See 49, A-6)
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|
| glycolysis (gli-kol_ùõ-sis) | The anaerobic conversion of glucose to lactic acid by use of the Embden-Meyerhof pathway.
(See 176)
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|
| glycolytic pathway (gli_ko-lit_ik) | See Embden-Meyerhof pathway.
(See 176, A-13)
|
|
|
|
| glyoxylate cycle (gli-ok_sùõ-lat) | A modified tricarboxylic acid cycle in which the decarboxylation reactions are bypassed by the enzymes isocitrate lyase and malate synthase; it is used to convert acetyl-CoA to succinate and other metabolites.
(See 216)
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|
|
| gnotobiotic (no_to-bi-ot_ik) | Animals that are germfree (microorganism free) or live in association with one or more known microorganisms.
(See 698)
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|
| Golgi apparatus (gol_je) | A membranous eucaryotic organelle composed of stacks of flattened sacs (cisternae), which is involved in packaging and modifying materials for secretion and many other processes.
(See 80)
|
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|
|
| gonococci (gon_o-kok_si) | Bacteria of the species Neisseria gonorrhoeae-the organism causing gonorrhea.
(See 915)
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|
|
| gonorrhea (gon_o-re_ah) | An acute infectious sexually transmitted disease of the mucous membranes of the genitourinary tract, eye, rectum, and throat. It is caused by Neisseria gonorrhoeae.
(See 915)
|
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|
|
| graft-versus-host disease | A disease that results when mature post-thymic T cells in donor grafts (e.g., bone marrow) recognize the host as foreign and attack it.
(See 773)
|
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|
|
| Gram stain | A differential staining procedure that divides bacteria into gram-positive and gram-negative groups based on their ability to retain crystal violet when decolorized with an organic solvent such as ethanol.
(See 28)
|
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|
|
| grana (gra_nah) | A stack of thylakoids in the chloroplast stroma.
(See 85)
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|
|
| granuloma (gran²u-lo_m@) | Term applied to nodular inflammatory lesions containing phagocytic cells.
(See 714)
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|
| 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.
(See 689)
|
|
|
|
| griseofulvin (gris²e-o-ful_vin) | An antibiotic from Penicillium griseofulvum given orally to treat chronic dermatophytic infections of skin and nails.
(See 820)
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|
|
| group translocation | A transport process in which a molecule is moved across a membrane by carrier proteins while being chemically altered at the same time.
(See 103)
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|
| growth | An increase in cellular constituents.
(See 113)
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|
| growth factors | Organic compounds that must be supplied in the diet for growth because they are essential cell components or precursors of such components and cannot be synthesized by the organism.
(See 99)
|
|
|
|
| guanine (gwan_in) | A purine derivative, 2-amino-6-oxypurine, found in nucleosides, nucleotides, and nucleic acids.
(See 217)
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|
|
| Guillain-Barr syndrome (ge-yan_bar-ra_) | 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.
(See 874)
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|
|
| gumma (gum_ah) | A soft, gummy tumor occurring in tertiary syphilis.
(See 924)
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|
|
| gut-associated lymphoid tissue (GALT) | The defensive lymphoid tissue present in the intestines. See Peyer's patches.
(See 710)
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|
| H-2 complex | Term for the MHC in the mouse.
(See 745)
|
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|
| halobacteria or extreme halophiles | A group of archaea that have an absolute dependence on high NaCl concentrations for growth and will not survive at a concentration below about 1.5 M NaCl.
(See 461)
|
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|
|
| halophile (hal_o-føõl) | A microorganism that requires high levels of sodium chloride for growth.
(See 123)
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|
| Hansen's disease | See leprosy.
(See 916)
|
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|
| hantavirus pulmonary syndrome | The disease in humans caused by the pulmonary syndrome hantavirus. Deer mice shed the virus in their feces, humans inhale the virus and first develop ordinary flulike aches and pains. Within a few days the hantavirus causes lung damage and capillary leakage. After about a week the infected person enters a crisis phase and may die.
(See 877)
|
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|
| hapten (hap_ten) | A molecule not immunogenic by itself but that, when coupled to a macromolecular carrier, can elicit antibodies directed against itself.
(See 731)
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|
| harborage transmission | The mode of transmission in which an infectious organism does not undergo morphological or physiological changes within the vector.
(See 858)
|
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| hay fever | Allergic rhinitis; a type of atopic allergy involving the upper respiratory tract.
(See 768)
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|
| health (helth) | A state of optimal physical, mental, and social well-being, and not merely the absence of disease and infirmity.
(See 848)
|
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|
|
| healthy carrier | An individual who harbors a pathogen, but is not ill.
(See 854)
|
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|
| heat-shock proteins | Proteins produced when cells are exposed to high temperatures or other stressful conditions. They protect the cells from damage and often aid in the proper folding of proteins.
(See 273)
|
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|
|
| helical (hel_ùõ-kal) | In virology this refers to a virus with a helical capsid surrounding its nucleic acid.
(See 369)
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|
|
| helicases | Enzymes that use ATP energy to unwind DNA ahead of the replication fork.
(See 236)
|
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|
|
| hemadsorption (hem²ad-sorp_shun) | The adherence of red blood cells to the surface of something, such as another cell or a virus.
(See 832)
|
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|
|
| hemagglutination (hem²ah-gloo²tùõ-na_shun) | The agglutination of red blood cells by antibodies.
(See 756)
|
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|
|
| hemagglutinin (hem²ah-gloo_tùõ-nin) | The antibody responsible for a hemagglutination reaction.
(See 756)
|
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|
|
| hemoflagellate (he²mo-flaj_ùe-løøat) | A flagellated protozoan parasite that is found in the bloodstream.
(See 956)
|
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|
|
| hemolysin (he-mol_ùõ-sin) | A substance that causes hemolysis (the lysis of red blood cells). At least some hemolysins are enzymes that destroy the phospholipids in erythrocyte plasma membranes.
(See 797)
|
|
|
|
| hemolysis (he-mol_ùõ-sis) | 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 a-hemolysis, a narrow greenish zone of incomplete hemolysis forms around the colony. A clear zone of complete hemolysis without any obvious color change is formed during b-hemolysis.
(See 531, 797)
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| 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.
(See 932)
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|
| hemorrhagic fever | A fever usually caused by a specific virus that may lead to hemorrhage, shock, and sometimes death.
(See 877)
|
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|
|
| hepatitis (hep²ah-ti_tis) | Any infection that results in inflammation of the liver. Also refers to liver inflammation as such.
(See 889)
|
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|
|
| hepatitis A (formerly infectious hepatitis; hep²ah-ti_tis) | 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 single-stranded RNA virus.
(See 892)
|
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|
|
| hepatitis B (formerly serum hepatitis; hep²ah-ti_tis) | This form of hepatitis is caused by a double-stranded DNA virus (HBV) formerly called the "Dane particle." The virus is transmitted by body fluids.
(See 889)
|
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|
|
| 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).
(See 890)
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|
|
| hepatitis D (formerly delta hepatitis) | The liver diseases caused by the hepatitis D virus in those individuals already infected with the hepatitis B virus.
(See 891)
|
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|
|
| 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.
(See 892)
|
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|
|
| herd immunity | The resistance of a population to infection and spread of an infectious organism due to the immunity of a high percentage of the population.
(See 851)
|
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|
|
| herpes labialis | See cold sore.
(See 884)
|
|
|
|
| herpetic keratitis (her-pet_ik ker²ah-ti_tis) | An inflammation of the cornea and conjunctiva of the eye resulting from a herpes simplex virus infection.
(See 884)
|
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|
|
| heterocysts | Specialized cells produced by cyanobacteria that are the sites of nitrogen fixation.
(See 473)
|
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|
|
| heteroduplex DNA | A double-stranded stretch of DNA formed by two slightly different strands that are not completely complementary.
(See 292)
|
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|
|
| heterogeneous nuclear RNA (hnRNA) | The RNA transcript of DNA made by RNA polymerase II; it is then processed to form mRNA.
(See 263)
|
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|
|
| heterolactic fermenters (het_er-o-lak_tik) | Microorganisms that ferment sugars to form lactate, and also other products such as ethanol and CO2.
(See 181)
|
|
|
|
| heterotroph (het_er-o-trøof_) | An organism that uses reduced, preformed organic molecules as its principal carbon source.
(See 96)
|
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|
|
| heterotrophic nitrification | Nitrification carried out by chemoheterotrophic microorganisms.
(See 615)
|
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|
|
| hexon or hexamer | A capsomer composed of six protomers.
(See 370)
|
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|
|
| hexose monophosphate pathway (hek_søos mon_o-fos_føøat) | See pentose phosphate pathway.
(See 177)
|
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|
|
| Hfr strain | A bacterial strain that donates its genes with high frequency to a recipient cell during conjugation because the F factor is integrated into the bacterial chromosome.
(See 303)
|
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|
|
| high-energy molecule | A molecule whose hydrolysis under standard conditions makes available a large amount of free energy (the standard free energy change is more negative than about 27 kcal/mole); a high-energy molecule readily decomposes and transfers groups such as phosphate to acceptors.
(See 157)
|
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|
|
| high oxygen diffusion environment | A microbial environment in close contact with air and through which oxygen can move at a rapid rate (in comparison with the slow diffusion rate of oxygen through water).
(See 635)
|
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|
|
| histone (his_tøon) | A small basic protein with large amounts of lysine and arginine that is associated with eucaryotic DNA in chromatin.
(See 234)
|
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|
|
| histoplasmosis (his_to-plaz-mo_sis) | A systemic fungal infection caused by Histoplasma capsulatum var capsulatum.
(See 947)
|
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|
|
| hives (hùõvz) | An eruption of the skin.
(See 769)
|
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|
|
| holdfast | A structure produced by some bacteria and algae that attaches the cell to a solid object.
(See 491)
|
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|
|
| holoenzyme | A complete enzyme consisting of the apoenzyme plus a cofactor.
(See 161)
|
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|
|
| holozoic nutrition (hol_o-zo_ik) | In this type of nutrition, nutrients (such as bacteria) are acquired by phagocytosis and the subsequent formation of a food vacuole or phagosome.
(See 586)
|
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|
|
| homolactic fermenters (ho_mo-lak_tik) | Organisms that ferment sugars almost completely to lactic acid.
(See 181)
|
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|
|
| horizontal gene transfer | The process in which genes are transferred from one mature, independent organism to another.
(See 292)
|
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|
|
| hormogonia | Small motile fragments produced by fragmentation of filamentous cyanobacteria; used for asexual reproduction and dispersal.
(See 473)
|
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|
|
| host (høost) | 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.
(See 788)
|
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|
|
| host restriction | The degradation of foreign genetic material by nucleases after the genetic material enters a host cell.
(See 294)
|
|
|
|
| human herpesvirus 6 (HHV-6, type A and B) (h@r_pøez) | HHV-6 was discovered in 1986 and was initially called the human B-lymphotropic virus. The virus was later shown to have a marked tropism for CD41 T cells and was renamed HHV-6. HHV-6 is genetically similar to cytomegalovirus. HHV-6 causes exanthem subitum (roseola infantum or sixth disease) in infants and has been suspected of involvement in many conditions, including opportunistic infections in immunocompromised patients, hepatitis, lymphoproliferative diseases, synergistic interactions with HIV, lymphadenitis, and chronic fatigue syndrome.
(See 887)
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|
|
|
| human immunodeficiency virus (HIV) | A lentivirus of the family Retroviridae that is associated with the onset of AIDS.
(See 878)
|
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|
|
| human leukocyte antigen complex (HLA) | An antigen on the surface of cells of human tissues and organs that is recognized by the immune system cells and therefore is important in graft rejection and regulation of the immune response. This is the same as MHC class II.
(See 745)
|
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|
|
| humoral (antibody-mediated) immunity (hu_mor-al) | The type of immunity that results from the presence of soluble antibodies in blood and lymph; also known as antibody-mediated immunity.
(See 729)
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|
|
| hybridoma (hi_brùõ-do_mah) | A fast-growing cell line produced by fusing a cancer cell (myeloma) to another cell, such as an antibody-producing cell.
(See 743)
|
|
|
|
| hydrogenosome (hi-dro-jen_osom) | A microbodylike organelle that contains a unique electron transfer pathway in which hydrogenase transfers electrons to protons (which act as the terminal electron acceptors) and molecular hydrogen is formed.
(See 585)
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|
|
| hydrophilic (hi_dro-fil_ik) | A polar substance that has a strong affinity for water (or is readily soluble in water).
(See 46)
|
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|
|
| hydrophobic (hi²dro-fo_bik) | A nonpolar substance lacking affinity for water (or which is not readily soluble in water).
(See 46)
|
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|
|
| hyperendemic disease (hi²per-en-dem_ik) | A disease that has a gradual increase in occurrence beyond the endemic level, but not at the epidemic level, in a given population; also may refer to a disease that is equally endemic in all age groups.
(See 849)
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|
|
| 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.
(See 246)
|
|
|
|
| hypersensitivity (hi²per-sen_si-tiv²i-te) | A condition of increased immune sensitivity in which the body reacts to an antigen with an exaggerated immune response that usually harms the individual. Also termed an allergy.
(See 768)
|
|
|
|
| hyperthermophile (hi²per-ther_mo-fùõl) | A bacterium that has its growth optimum between 80 degrees C and about 113 degrees C. Hyperthermophiles usually do not grow well below 55 degrees C.
(See 126, 626)
|
|
|
|
| hypha (hi_fah; pl., hyphae) | The unit of structure of most fungi and some bacteria; a tubular filament.
(See 556)
|
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|
|
| hypoferremia (hi²po-fùe-re_me-ah) | Deficiency of iron in the blood.
(See 723)
|
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|
|
| hypotheca (hi-po-theca) | The smaller half of a diatom frustule.
(See 577)
|
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|
|
| hypothesis | A tentative assumption or educated guess developed to explain a set of observations.
(See 8)
|
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|
|
| hypoxic (hi pok_sik) | Having a low oxygen level.
(See 635)
|
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|
|
| icosahedral | In virology this term refers to a virus with an icosahedral capsid, which has the shape of a regular polyhedron having 20 equilateral triangular faces and 12 corners.
(See 369)
|
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|
|
| identification (i-den_tùõ-fùõ-ka_shun) | The process of determining that a particular isolate or organism belongs to a recognized taxon.
(See 422)
|
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|
|
| idiotype (id_e-o-tøõp_) | A set of one or more unique epitopes in the variable region of an immunoglobulin that distinguishes it from immunoglobulins produced by different plasma cells.
(See 734)
|
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|
|
| IgA | Immunoglobulin A; the class of immunoglobulins that is present in dimeric form in many body secretions (e.g., saliva, tears, and bronchial and intestinal secretions) and protects body surfaces. IgA also is present in serum.
(See 736)
|
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|
|
| IgD | Immunoglobulin D; the class of immunoglobulins found on the surface of many B lymphocytes; thought to serve as an antigen receptor in the stimulation of antibody synthesis.
(See 738)
|
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|
|
| IgE | Immunoglobulin E; the immunoglobulin class that binds to mast cells and basophils, and is responsible for type I or anaphylactic hypersensitivity reactions such as hay fever and asthma. IgE is also involved in resistance to helminth parasites.
(See 738)
|
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|
|
| IgG | Immunoglobulin G; the predominant immunoglobulin class in serum. Has functions such as neutralizing toxins, opsonizing bacteria, activating complement, and crossing the placenta to protect the fetus and neonate.
(See 736)
|
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|
|
| IgM | Immunoglobulin M; the class of serum antibody first produced during an infection. It is a large, pentameric molecule that is active in agglutinating pathogens and activating complement. The monomeric form is present on the surface of some B lymphocytes.
(See 736)
|
|
|
|
| immobilization (im-mo_bil-i-za_shun) | The incorporation of a simple, soluble substance into the body of an organism, making it unavailable for use by other organisms.
(See 613)
|
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|
|
| immune complex (ùõ-møun_kom_pleks) | The product of an antigen-antibody reaction, which may also contain components of the complement system.
(See 756)
|
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|
|
| immune surveillance (ùõ-møun_sur-vøal_ans) | The still somewhat hypothetical process in which lymphocytes such as natural killer (NK) cells recognize and destroy tumor cells; other cells with abnormal surface antigens (e.g., virus-infected cells) also may be destroyed.
(See 760)
|
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|
| immune system | The defensive system in a host consisting of the nonspecific and specific immune responses. It is composed of widely distributed cells, tissues, and organs that recognize foreign substances and microorganisms and acts to neutralize or destroy them.
(See 705)
|
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|
|
| immunity (ùõ-mu_nùõ-te) | Refers to the overall general ability of a host to resist a particular disease; the condition of being immune.
(See 705)
|
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|
|
| immunoblotting | The electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets to demonstrate the presence of specific proteins through reaction with labeled antibodies.
(See 779)
|
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|
|
| immunodeficiency (im²u-no-dùe-fish_en-se; pl., immunodeficiencies) | The inability to produce a normal complement of antibodies or immunologically sensitized T cells in response to specific antigens.
(See 774)
|
|
|
|
| immunodiffusion | A technique involving the diffusion of antigen and/or antibody within a semisolid gel to produce a precipitin reaction where they meet in proper proportions. Often both the antibody and antigen diffuse through the gel; sometimes an antigen diffuses through a gel containing antibody.
(See 779)
|
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|
|
| immunoelectrophoresis (ùõ-mu_no-e-lek_tro-fo-re_sis; pl., immunoelectrophoreses) | The electrophoretic separation of protein antigens followed by diffusion and precipitation in gels using antibodies against the separated proteins.
(See 781)
|
|
|
|
| immunofluorescence (im_u-no-floo_o-res_ens) | A technique used to identify particular antigens microscopically in cells or tissues by the binding of a fluorescent antibody conjugate.
(See 781)
|
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|
|
| immunoglobulin (Ig; im_u-no-glob_u-lin) | See antibody.
(See 734)
|
|
|
|
| immunology (im_u-nol_o-je) | The branch of science that deals with the immune system and attempts to understand the many phenomena that are responsible for both acquired and innate immunity. It also includes the use of antibody-antigen reactions in other laboratory work (serology and immunochemistry).
(See 705)
|
|
|
|
| immunopathology (im_u-no-p@-thol_o-je) | The study of diseases or conditions resulting from immune reactions.
(See 790)
|
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| immunoprecipitation (im_u-no-pre-sip_i-ta_shun) | A reaction involving soluble antigens reacting with antibodies to form a large aggregate that precipitates out of solution.
(See 781)
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| immunotoxin (im_u-no-tok_sin) | A monoclonal antibody that has been attached to a specific toxin or toxic agent (antibody 1 toxin 5 immunotoxin) and can kill specific target cells.
(See 744)
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| impetigo (im_p@-ti_go) | This superficial cutaneous disease, most commonly seen in children, is characterized by crusty lesions, usually located on the face; the lesions typically have vesicles surrounded by a red border. It is the most frequently diagnosed skin infection caused by S. pyogenes (impetigo can also be caused by S. aureus).
(See 903)
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| inclusion bodies | Granules of organic or inorganic material lying in the cytoplasmic matrix of bacteria.
(See 49, 410)
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| inclusion conjunctivitis (in-klu_zhun kon-junk_tùõ-vi_tis) | An acute infectious disease that occurs throughout the world. It is caused by Chlamydia trachomatis that infects the eye and causes inflammation and the occurrence of large inclusion bodies.
(See 916)
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| incubation period | The period after pathogen entry into a host and before signs and symptoms appear.
(See 850)
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| incubatory carrier | An individual who is incubating a pathogen in large numbers but is not yet ill.
(See 854)
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| index case | The first disease case in an epidemic within a given population.
(See 849)
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| 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.
(See 654)
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| inducer (in-døus_er) | A small molecule that stimulates the synthesis of an inducible enzyme.
(See 275)
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| inducible enzyme | An enzyme whose level rises in the presence of a small molecule that stimulates its synthesis.
(See 275)
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| industrial ecology | The study of the ecology of industrial societies with a major focus on material cycling, energy flow, and the ecological impacts of such societies.
(See 1022)
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| infantile paralysis (in_fan-til pah-ral_i-sis) | See poliomyelitis.
(See 892)
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| infection (in-fek_shun) | 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.
(See 789)
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| 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.
(See 676)
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| infectious disease | Any change from a state of health in which part or all of the host's body cannot carry on its normal functions because of the presence of an infectious agent or its products.
(See 789)
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| infectious disease cycle (chain of infection) | The chain or cycle of events that describes how an infectious organism grows, reproduces, and is disseminated.
(See 852)
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| 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.
(See 368, 790)
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| infectious mononucleosis (mono; mon_o-nu_kle-o_sis) | An acute, self-limited infectious disease of the lymphatic system caused by the Epstein-Barr virus and characterized by fever, sore throat, lymph node and spleen swelling, and the proliferation of monocytes and abnormal lymphocytes.
(See 888)
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| infectivity (in_fek-tiv_i-te) | Infectiousness; the state or quality of being infectious or communicable.
(See 790)
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| inflammation (in_flah-ma_shun) | A localized protective response to tissue injury or destruction. Acute inflammation is characterized by pain, heat, swelling, and redness in the injured area.
(See 712)
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| influenza or flu (in_flu-en_zah) | An acute viral infection of the respiratory tract, occurring in isolated cases, epidemics, and pandemics. Influenza is caused by three strains of influenza virus, labeled types A, B, and C, based on the antigens of their protein coats.
(See 872)
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| ingoldian fungi | Aquatic hyphomycetes that often have a characteristic tetraradiate hyphal development form and which sporulate under water. Discovered by the British mycologist, C. T. Ingold, in the 1940s.
(See 641)
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| initial body | See reticulate body (RB).
(See 477)
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| innate or natural immunity | See nonspecific resistance.
(See 705)
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| insertion sequence (in-ser_shun se_kwens) | A simple transposon that contains genes only for those enzymes, such as the transposase, that are required for transposition.
(See 298)
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| 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.
(See 394)
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| integrins (in_t@-grin) | A large and broadly distributed family of a/b heterodimers. Integrins are cellular adhesion receptors that mediate cell-cell and cell-substratum interactions. Integrins usually recognize linear amino acid sequences on protein ligands.
(See 712)
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| inteins | Internal intervening sequences of precursor self-splicing proteins that separate exteins and are removed during formation of the final protein.
(See 275)
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| intercalating agents | Molecules that can be inserted between the stacked bases of a DNA double helix, thereby distorting the DNA and inducing insertion and deletion mutations.
(See 248)
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| interdigitating dendritic cell | Special dendritic cells in the lymph nodes that function as potent antigen-presenting cells and develop from Langerhans cells.
(See 710)
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| interferon (IFN; in²t@r-føer_on) | 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.
(See 721, 822)
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| interleukin (in²t@r-loo_kin) | A glycoprotein produced by macrophages and T cells that regulates growth and differentiation, particularly of lymphocytes. Interleukins promote cellular and humoral immune responses.
(See 720)
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| intermediate filaments (in²ter-me_de-it fil_ah-ments) | Small protein filaments, about 8 to 10 nm in diameter, in the cytoplasmic matrix of eucaryotic cells that are important in cell structure.
(See 79)
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| intermediate host (in²ter-me_de-it høost) | The host that serves as a temporary but essential environment for development of a parasite and completion of its life cycle.
(See 789)
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| 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.
(See 604)
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| 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).
(See 950)
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| intoxication (in-tok²si-ka_shun) | 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 organism.
(See 794)
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| intraepidermal lymphocytes | T cells found in the epidermis of the skin that express the gd T-cell receptor.
(See 710)
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| intranuclear inclusion body (in²trah-nu_kel-ar) | A structure found within cells infected with the cytomegalovirus.
(See 885)
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| intrinsic factors | Food-related factors such as moisture, pH, and available nutrients that influence microbial growth.
(See 964)
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| intron (in_tron) | A noncoding intervening sequence in a split or interrupted gene, which codes for RNA that is missing from the final RNA product.
(See 263)
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| invasiveness (in-va_siv-nes) | The ability of a microorganism to enter a host, grow and reproduce within the host, and spread throughout its body.
(See 790)
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| ionizing radiation | Radiation of very short wavelength or high energy that causes atoms to lose electrons or ionize.
(See 130, 144)
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| isotype (i_so-tøõp) | A variant form of an immunoglobulin (e.g., an immunoglobulin class, subclass, or type) that occurs in every normal individual of a particular species. Usually the characteristic antigenic determinant is in the constant region of H and L chains.
(See 734)
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| Jaccard coefficient (SJ) | An association coefficient used in numerical taxonomy; it is the proportion of characters that match, excluding those that both organisms lack.
(See 427)
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| J chain | A polypeptide present in polymeric IgM and IgA that links the subunits together.
(See 736)
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| jock itch | See tinea cruris.
(See 944)
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| kelp (kelp) | A common name for any of the larger members of the order Laminariales of the brown algae.
(See 578)
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| keratinocyte | Cell found in skin-associated lymphoid tissue; secretes cytokines that may induce an inflammatory response.
(See 709)
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| keratitis (ker_ah-ti_tis) | Inflammation of the cornea of the eye.
(See 953)
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| kinetoplast (ki-ne_to-plast) | A special structure in the mitochondrion of kinetoplastid protozoa. It contains the mitochondrial DNA.
(See 588)
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| Kirby-Bauer method | A disk diffusion test to determine the susceptibility of a microorganism to chemotherapeutic agents.
(See 809)
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| Koch's postulates (koks pos_tu-løats) | A set of rules for proving that a microorganism causes a particular disease.
(See 7)
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| Koplik's spots (kop_liks) | Lesions of the oral cavity caused by the measles (rubeola) virus that are characterized by a bluish white speck in the center of each.
(See 874)
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| Korean hemorrhagic fever | An acute infection caused by a virus that produces varying degrees of hemorrhage, shock, and sometimes death. Krebs cycle See tricarboxylic acid (TCA)cycle.
(See 183, 877)
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| lactic acid fermentation (lak_tik) | A fermentation that produces lactic acid as the sole or primary product.
(See 179, A-19)
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| lager | Pertaining to the process of aging beers to allow flavor development.
(See 983)
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| 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.
(See 113)
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| laminarin (lam_i-na_rin) | One of the principal storage products of the golden-brown algae; a polymer of glucose.
(See 578)
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| Lancefield system (group; lans_feld) | One of the serologically distinguishable groups (as group A, group B) into which streptococci can be divided.
(See 532, 784)
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| land farming | The addition of waste material, such as a hydrocarbon waste, to the soil surface so that it will be degraded. The soil may be moistened or mixed to stimulate the desired degradation process.
(See 1011)
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| Langerhans cell | Cell found in the skin that internalizes antigen and moves in the lymph to lymph nodes where it differentiates into a dendritic cell.
(See 709)
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| late mRNA | Messenger RNA produced later in a virus infection, which codes for proteins needed in capsid construction and virus release.
(See 387)
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| latent period (la_tent) | The initial phase in the one-step growth experiment in which no phages are released.
(See 383)
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| latent virus infections | Virus infections in which the virus quits reproducing and remains dormant for a period before becoming active again.
(See 410)
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| leader sequence | A nontranslated sequence at the 5_ end of mRNA that lies between the operator and the initiation codon; it aids in the initiation and regulation of transcription.
(See 244, 261)
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| lectin complement pathway (lek_tin) | 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.
(See 716)
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| legionellosis (le_j@-nel-o_sis) | See Legionnaires' disease.
(See 901)
|
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|
| Legionnaires' disease (legionellosis) | A pulmonary form of legionellosis, resulting from infection with Legionella pneumophila.
(See 901)
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|
| leishmanias (løesh_ma_ne-ùas) | Zooflagellates, members of the genus Leishmania, that cause the disease leishmaniasis.
(See 956)
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| leishmaniasis (løesh_mah-ni_ah-sis) | The disease caused by the protozoa called leishmanias.
(See 956)
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|
| lepromatous (progressive) leprosy (lep-ro_mah-tus lep_ro-se) | A relentless, progressive form of leprosy in which large numbers of Mycobacterium leprae develop in skin cells, killing the skin cells and resulting in the loss of features. Disfiguring nodules form all over the body.
(See 916)
|
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|
|
| leprosy (lep_ro-se) or Hansen's disease | A severe disfiguring skin disease caused by Mycobacterium leprae.
(See 916)
|
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|
| 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.
(See 368, 790)
|
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|
|
| leukemia (loo-ke_me-ah) | 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).
(See 887)
|
|
|
|
| leukocidin (loo_ko-si_din) | A microbial toxin that can damage or kill leukocytes.
(See 797)
|
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|
|
| leukocyte (loo_ko-søõt) | Any colorless white blood cell. Can be classified into granular and agranular lymphocytes.
(See 705)
|
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|
|
| lichen (li_ken) | An organism composed of a fungus and either green algae or cyanobacteria in a symbiotic association.
(See 598)
|
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|
|
| Liebig's law of the minimum (le_bigz) | Living organisms and populations will grow until lack of a resource begins to limit further growth.
(See 131)
|
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|
|
| lipopolysaccharide (lip_o-pol_e-sak_ah-røõd) | A molecule containing both lipid and polysaccharide, which is important in the outer membrane of the gram-negative cell wall.
(See 58)
|
|
|
|
| liposome (lip_o-som) | A spherical particle formed by a lipid bilayer enclosing an aqueous solution. It may be used to administer chemotherapeutic agents or in diagnostic testing.
(See 782)
|
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|
|
| listeriosis (lis-ter_e-o_sis) | A sporadic disease of animals and humans, particularly those who are immunocompromised or pregnant, caused by the bacterium Listeria monocytogenes.
(See 931)
|
|
|
|
| lithotroph (lith_o-trøof) | An organism that uses reduced inorganic compounds as its electron source.
(See 97)
|
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|
|
| log phase | See exponential phase.
(See 114)
|
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|
|
| lophotrichous (lo-fot_rùõ-kus) | A cell with a cluster of flagella at one or both ends.
(See 63)
|
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|
|
| 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.
(See 635)
|
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|
|
| 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.
(See 801)
|
|
|
|
| Lyme disease (LD, Lyme borreliosis; løõm) | A tick-borne disease caused by the spirochete Borrella burgdorferi.
(See 910)
|
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|
|
| lymph node | A small secondary lymphoid organ that contains lymphocytes, macrophages, and dendritic cells. It serves as a site for (1) filtration and removal of foreign antigens and (2) the activation and proliferation of lymphocytes.
(See 709)
|
|
|
|
| lymphocyte (lim_fo-søõt) | A nonphagocytic, mononuclear leukocyte (white blood cell) that is an immunologically competent cell, or its precursor. Lymphocytes are present in the blood, lymph, and lymphoid tissues. See B cell and T cell.
(See 705)
|
|
|
|
| lymphogranuloma venereum (LGV; lim_fo-gran_u-lo_mah) | A sexually transmitted disease caused by Chlamydia trachomatis serotypes L1-L3, which affect the lymph organs in the genital area.
(See 917)
|
|
|
|
| lymphokine (lim_fo-kin) | A biologically active glycoprotein (e.g., IL-1) secreted by activated lymphocytes, especially sensitized T cells. It acts as an intercellular mediator of the immune response and transmits growth, differentiation, and behavioral signals.
(See 720)
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|
|
| lysis (li_sis) | The rupture or physical disintegration of a cell.
(See 61)
|
|
|
|
| lysogenic (li-so-jen_ik) | See lysogens.
(See 308, 390)
|
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|
|
| lysogens (li_so-jens) | Bacteria that are carrying a viral prophage and have the potential of producing bacteriophages under the proper conditions.
(See 308, 390)
|
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|
|
| lysogeny (li-soj_e-ne) | The state in which a phage genome remains within the bacterial host cell after infection and reproduces along with it rather than taking control of the host and destroying it.
(See 307, 390)
|
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|
|
| lysosome (li_so-søom) | A spherical membranous eucaryotic organelle that contains hydrolytic enzymes and is responsible for the intracellular digestion of substances.
(See 80)
|
|
|
|
| lysozyme (li_søo-zøõm) | An enzyme that degrades peptidoglycan by hydrolyzing the b(1 _ 4) bond that joins N-acetylmuramic acid and N-acetylglucosamine.
(See 61, 710)
|
|
|
|
| lytic cycle (lit_ik) | A virus life cycle that results in the lysis of the host cell.
(See 383)
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2002 McGraw-Hill Higher Education