Microbiology Glossary Terms - G, H MSUTIB

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G, H Terms

gametangium

A structure that contains gametes or in which gametes are formed.
(See page(s) 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 page(s) 498)

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.
(See page(s) 915)

gastritis

Inflammation of the stomach.
(See page(s) 918)

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 (campylobacteriosis), and Salmonella species; consumption of irritating food or drink; or psychological factors such as anger, stress, and fear. Also called enterogastritis.
(See page(s) 929)

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 page(s) 51)

gene

A DNA segment or sequence that codes for a polypeptide, rRNA, or tRNA.
(See page(s) 241)

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 page(s) 335)

generalized transduction

The transfer of any part of a bacterial genome when the DNA fragment is packaged within a phage capsid by mistake.
(See page(s) 308)

general recombination

Recombination involving a reciprocal exchange of a pair of homologous DNA sequences; it can occur any place on the chromosome.
(See page(s) 292)

generation time

The time required for a microbial population to double in number.
(See page(s) 115)

genetic engineering

The deliberate modification of an organism's genetic information by directly changing its nucleic acid genome.
(See page(s) 320)

genital herpes

A sexually transmitted disease caused by the herpes simplex virus type 2.
(See page(s) 885)

genital ulcer disease

See chancroid.
(See page(s) 914)
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.
(See page(s) 914)

genome

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 page(s) 228)

genomics

The study of the molecular organization of genomes, their information content, and the gene products they encode.
(See page(s) 345)

genus

A well-defined group of one or more species that is clearly separate from other genera.
(See page(s) 426)

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 page(s) 850)

German measles

See rubella.
(See page(s) 875)
A moderately contagious skin disease that occurs primarily in children 5 to 9 years of age that is caused by the rubella virus, which is acquired by droplet inhalation into the respiratory system; German measles.
(See page(s) 875)

germicide

An agent that kills pathogens and many nonpathogens but not necessarily bacterial endospores.
(See page(s) 138)

germination

The stage following bacterial endospore activation in which the endospore breaks its dormant state. Germination is followed by outgrowth.
(See page(s) 71)

Ghon complex (gon)

The initial focus of parenchymal infection in primary pulmonary tuberculosis.
(See page(s) 908)

giardiasis

A common intestinal disease caused by the parasitic protozoan Giardia lamblia.
(See page(s) 953)

gingivitis

Inflammation of the gingival tissue.
(See page(s) 936)

gingivostomatitis

Inflammation of the gingiva and other oral mucous membranes.
(See page(s) 884)

gliding motility

A type of motility in which a microbial cell glides along when in contact with a solid surface.
(See page(s) 66, 482)

global regulatory systems

Regulatory systems that simultaneously affect many genes and pathways.
(See page(s) 281)

glomerulonephritis

An inflammatory disease of the renal glomeruli.
(See page(s) 905)

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 page(s) 936)

gluconeogenesis

The synthesis of glucose from noncarbohydrate precursors such as lactate and amino acids.
(See page(s) 209)

glycocalyx

A network of polysaccharides extending from the surface of bacteria and other cells.
(See page(s) 61)

glycogen

A highly branched polysaccharide containing glucose, which is used to store carbon and energy.
(See page(s) 49, A-6)

glycolysis

The anaerobic conversion of glucose to lactic acid by use of the Embden-Meyerhof pathway.
(See page(s) 176)

glycolytic pathway

See Embden-Meyerhof pathway.
(See page(s) 176, A-13)
A pathway that degrades glucose to pyruvate; the six-carbon stage converts glucose to fructose 1,6-bisphosphate, and the three-carbon stage produces ATP while changing glyceraldehyde 3-phosphate to pyruvate.
(See page(s) 176, A-13)

glyoxylate cycle

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 page(s) 216)

gnotobiotic

Animals that are germfree (microorganism free) or live in association with one or more known microorganisms.
(See page(s) 698)

Golgi apparatus

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 page(s) 80)

gonococci

Bacteria of the species Neisseria gonorrhoeae-the organism causing gonorrhea.
(See page(s) 915)

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.
(See page(s) 915)

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 page(s) 773)

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 page(s) 28)

grana

A stack of thylakoids in the chloroplast stroma.
(See page(s) 85)

granuloma

Term applied to nodular inflammatory lesions containing phagocytic cells.
(See page(s) 714)

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 page(s) 689)

griseofulvin

An antibiotic from Penicillium griseofulvum given orally to treat chronic dermatophytic infections of skin and nails.
(See page(s) 820)

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 page(s) 103)

growth

An increase in cellular constituents.
(See page(s) 113)

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 page(s) 99)

guanine

A purine derivative, 2-amino-6-oxypurine, found in nucleosides, nucleotides, and nucleic acids.
(See page(s) 217)

Guillain-Barr 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.
(See page(s) 874)

gumma

A soft, gummy tumor occurring in tertiary syphilis.
(See page(s) 924)

gut-associated lymphoid tissue (GALT)

The defensive lymphoid tissue present in the intestines. See Peyer's patches.
(See page(s) 710)

H-2 complex

Term for the MHC in the mouse.
(See page(s) 745)

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 page(s) 461)

halophile

A microorganism that requires high levels of sodium chloride for growth.
(See page(s) 123)

Hansen's disease

See leprosy.
(See page(s) 916)
A severe disfiguring skin disease caused by Mycobacterium leprae.
(See page(s) 916)

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 page(s) 877)

hapten

A molecule not immunogenic by itself but that, when coupled to a macromolecular carrier, can elicit antibodies directed against itself.
(See page(s) 731)

harborage transmission

The mode of transmission in which an infectious organism does not undergo morphological or physiological changes within the vector.
(See page(s) 858)

hay fever

Allergic rhinitis; a type of atopic allergy involving the upper respiratory tract.
(See page(s) 768)

health

A state of optimal physical, mental, and social well-being, and not merely the absence of disease and infirmity.
(See page(s) 848)

healthy carrier

An individual who harbors a pathogen, but is not ill.
(See page(s) 854)

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 page(s) 273)

helical

In virology this refers to a virus with a helical capsid surrounding its nucleic acid.
(See page(s) 369)

helicases

Enzymes that use ATP energy to unwind DNA ahead of the replication fork.
(See page(s) 236)

hemadsorption

The adherence of red blood cells to the surface of something, such as another cell or a virus.
(See page(s) 832)

hemagglutination

The agglutination of red blood cells by antibodies.
(See page(s) 756)

hemagglutinin

The antibody responsible for a hemagglutination reaction.
(See page(s) 756)

hemoflagellate

A flagellated protozoan parasite that is found in the bloodstream.
(See page(s) 956)

hemolysin

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 page(s) 797)

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 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 page(s) 531, 797)

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 page(s) 932)

hemorrhagic fever

A fever usually caused by a specific virus that may lead to hemorrhage, shock, and sometimes death.
(See page(s) 877)

hepatitis

Any infection that results in inflammation of the liver. Also refers to liver inflammation as such.
(See page(s) 889)

hepatitis A

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 page(s) 892)

hepatitis B

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 page(s) 889)

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 page(s) 890)

hepatitis D

The liver diseases caused by the hepatitis D virus in those individuals already infected with the hepatitis B virus.
(See page(s) 891)

hepatitis E

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 page(s) 892)

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.

herpes labialis

See cold sore.
(See page(s) 884)
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.
(See page(s) 884)

herpetic keratitis

An inflammation of the cornea and conjunctiva of the eye resulting from a herpes simplex virus infection.
(See page(s) 884)

heterocysts

Specialized cells produced by cyanobacteria that are the sites of nitrogen fixation.
(See page(s) 473)

heteroduplex DNA

A double-stranded stretch of DNA formed by two slightly different strands that are not completely complementary.
(See page(s) 292)

heterogeneous nuclear RNA (hnRNA)

The RNA transcript of DNA made by RNA polymerase II; it is then processed to form mRNA.
(See page(s) 263)

heterolactic fermenters

Microorganisms that ferment sugars to form lactate, and also other products such as ethanol and CO2.
(See page(s) 181)

heterotroph

An organism that uses reduced, preformed organic molecules as its principal carbon source.
(See page(s) 96)

heterotrophic nitrification

Nitrification carried out by chemoheterotrophic microorganisms.
(See page(s) 615)

hexon or hexamer

A capsomer composed of six protomers.
(See page(s) 370)

hexose monophosphate pathway

See pentose phosphate pathway.
(See page(s) 177)
The pathway that oxidizes glucose 6-phosphate to ribulose 5-phosphate and then converts it to a variety of three to seven carbon sugars; it forms several important products (NADPH for biosynthesis, pentoses, and other sugars) and also can be used to degrade glucose to CO2.
(See page(s) 177, A-14)

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 page(s) 303)

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 page(s) 157)

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 page(s) 635)

histone

A small basic protein with large amounts of lysine and arginine that is associated with eucaryotic DNA in chromatin.
(See page(s) 234)

histoplasmosis

A systemic fungal infection caused by Histoplasma capsulatum var capsulatum.
(See page(s) 947)

hives

An eruption of the skin.
(See page(s) 769)

holdfast

A structure produced by some bacteria and algae that attaches the cell to a solid object.
(See page(s) 491)

holoenzyme

A complete enzyme consisting of the apoenzyme plus a cofactor.
(See page(s) 161)

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.
(See page(s) 586)

homolactic fermenters

Organisms that ferment sugars almost completely to lactic acid.
(See page(s) 181)

horizontal gene transfer

The process in which genes are transferred from one mature, independent organism to another.
(See page(s) 292)

hormogonia

Small motile fragments produced by fragmentation of filamentous cyanobacteria; used for asexual reproduction and dispersal.
(See page(s) 473)

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.
(See page(s) 788)

host restriction

The degradation of foreign genetic material by nucleases after the genetic material enters a host cell.
(See page(s) 294)

human herpesvirus 6 (HHV-6, type A and B)

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 page(s) 887)

human immunodeficiency virus (HIV)

A lentivirus of the family Retroviridae that is associated with the onset of AIDS.
(See page(s) 878)

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 page(s) 745)

humoral (antibody-mediated) immunity

The type of immunity that results from the presence of soluble antibodies in blood and lymph; also known as antibody-mediated immunity.
(See page(s) 729)

hybridoma

A fast-growing cell line produced by fusing a cancer cell (myeloma) to another cell, such as an antibody-producing cell.
(See page(s) 743)

hydrogenosome

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 page(s) 585)

hydrophilic

A polar substance that has a strong affinity for water (or is readily soluble in water).
(See page(s) 46)

hydrophobic

A nonpolar substance lacking affinity for water (or which is not readily soluble in water).
(See page(s) 46)

hyperendemic disease

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 page(s) 849)

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 page(s) 246)

hypersensitivity

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 page(s) 768)

hyperthermophile

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 page(s) 126, 626)

hypha

hypha (hi_fah; pl., hyphae) The unit of structure of most fungi and some bacteria; a tubular filament.
(See page(s) 556)

hypoferremia

Deficiency of iron in the blood.
(See page(s) 723)

hypotheca

The smaller half of a diatom frustule.
(See page(s) 577)

hypothesis

A tentative assumption or educated guess developed to explain a set of observations.
(See page(s) 8)

hypoxic

Having a low oxygen level.
(See page(s) 635)

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