G-CSF : Granulocyte-macrophage colony-stimulating factor.

G-6-PD : Glucose-6-phosphate dehydrogenase (deficiency).

GABHS : Group A beta-hemolytic streptococcus.

Gait : Manner of walking.

Gamete : In eukaryotes, the haploid cell analogous to sperm and egg, which results from meiosis.

Gametocyte : In malaria, the sexual cell (male microgametocyte or female macrogametocyte). Occurs in peripheral blood; fertilization will occur in the mosquito stomach forming the zygote.

Gangrene : Death of part of tissue resulting from disease, injury, or failure of blood supply.

Gas-liquid chromatography : A chromatographic technique in which the stationary phase is solid while the mobile phase is gaseous samples. The gaseous samples are separated based on their different adsorption ability to the solid phase.

Gas vacuole : A cavity in the cytoplasm that contains gas of composition similar to that of the surrounding atmosphere. The boundary of the cavity is a membrane consisting of protein subunits. Gas vacuoles appear as bright areas within a cell by phase-contrast microscopy and are identified by their ability to collapse when the cells are subjected to a sudden increase in hydrostatic pressure.

Gas vesicle : The hollow, cylindrical, gas-fillled structure in the gas vacuole. It confers ability for gas vacuole to float.

Gas-liquid chromatography (GLC) : A method for separating substances by allowing their volatile phase to flow through a heated column with a carrier gas and measuring the time required to detect their presence at the distal end of the column.

Gastric aspirate : Fluid that may be aspirated from the stomach via a tube placed in the stomach by way of the nose or mouth.

Gastritis : Inflammation of the stomach, usually involving only the lining inside the organ.

Gastroenteritis : Inflammation of the mucosa of the stomach and intestines.

GC : Gonococcus or gonorrheal.

Gel : An inert polymer, usually made of agarose or polyacrylamide, used for separating macromolecules such as nucleic acids or proteins by electrophoresis.

Gene : A unit of heredity; a segment of DNA specifying a particular protein or polypeptide chain, a tRNA or a rRNA.

Gene amplification : See amplification.

Gene cloning : The isolation of a desired gene from one organism and its incorporation into a suitable vector for the production of large amounts of the gene.

Gene copy number : See copy number.

Gene disruption : Use of both in vitro and in vivo recombination to substitute an easily selected mutant gene for a wild-type gene.

Gene library : A collection of cloned DNA fragments that contains all the genetic information of a particular organism.

Gene therapy : Replacement or augmentation of a dysfunctional gene for medical purposes.

Generation time : Time needed for a population to double. See also doubling time.

Genetic code : The "code" in which information for the synthesis of proteins is contained in the nucleotide sequence of a DNA molecule (or in certain viruses of an RNA molecule).

Genetic engineering : The use of in vitro techniques in the isolation, manipulation, recombination, and expression of DNA.

Genetic map : The physical arrangement and order of genes on the chromosome.

Genetics : The science of studying heredity and variation of organisms.

Geniculate : Bent like a knew.

Genital primordium : Ovoid clump of cells that becomes the reproductive system (seen in the rhabditiform larvae of Strongyloides stercoralis and hookworm).

Genome : The complete set of genes present in an organism.

Genotype : The precise genetic constitution of an organism. Compare with phenotype.

Genus (plural genera) : The first name of the scientific name (binomial); the taxon between family and species.

Geophilic : Fungi whose natural habitat is in the soil.

Germ tube : A tubelike outgrowth from a conidium or spore; the beginning of a hypha.

Germicide : An agent that destroys germs; disinfectant.

GF : Gastric fluid, germ-free, glomerulaur filtration, growth factor.

GFR : Glomerular filtration rate.

GI : Gastrointestinal.

Glabrous : Smooth; without or almost without aerial hyphae.

GLC : Gas-liquid chromatography.

Gliding Motility : A type of movement across surfaces that is exhibited by some bacteria devoid of flagella and incapable of swimming motility.

Glomerulonephritis : Bilateral inflammatory changes of the glomeruli that are the result of renal disease rather than infection.

Glove box : A device with flexible, semirigid, or rigid plastic walls used for cultivation of anaerobic bacteria. Bacteriologist must work by way of glove ports, and materials are brought into and out of the anaerobic work area by way of an interchange (Airlock) that can be evacuated and refilled with an anaerobic atmosphere repeatedly until it itself is anaerobic. The interchange has one door leading into the glove box per se and another door to the outside. Some glove boxes have incubators within them. Also called anaerobic chamber or anaerobic cabinet.

Glycocalyx : General term for polysaccharide components outside the bacterial cell wall. See also capsule and slime layer.

Glycolysis : Reactions of the Embden-Meyerhof pathway in which glucose is oxidized to pyruvate.

Glycosidic bond : A type of covalent bond that links sugar units together in a polysaccharide.

Gm; g; gm : Gram(s).

GM-CSF : Granulocyte-macrophage colony-stimulating factor.

GN : Gram-negative (broth).

GNR : Gram-negative rods.

Golgi complex : An eukaryotic organelle involved in the secretion of certain proteins.

Gonococcus : Neisseria gonorrhoeae, the gram-negative diplococcus that causes the disease gonorrhea.

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.

Gram-negative : To describe a prokaryotic cell whose cell wall stains pink (negative) in Gram stain. The cell wall of a gram-negative bacterium contains relatively little peptidoglycan but contains an outer membrane composed of lipopolysaccharide (LPS), lipoprotein, and other complex macromolecules.

Gram-positive : To describe a prokaryotic cell whose cell wall stains purple (positive) in Gram stain. The cell wall of a gram-positive bacterium consists chiefly of peptidoglycan and lacks the outer membrane of gram-negative cells.

Gram stain : A differential stain that divides bacteria into two groups, gram-positive and gram-negative based on the ability to retain crystal violet when decolorized with an organic solvent such as ethanol.

Gram Variable : Some Gram-positive cells occur in an otherwise Gram-negative pure culture.

Granulocytopenia : Reduced number of granulocytic white blood cells int the blood.

Granuloma : Aggregation and proliferation of macrophages to form small (usually microscopic) nodules.

Granulomatous : Pertaining to or resembling a granuloma.

Green (sulfur) bacteria : Anoxygenic phototrophs containing chlorosomes and bacteriochlorophyll c, cs, d or e and light harvesting chlorophyll.

Growth : In microbiology, an increase in both cell number and cellular constituents.

Growth factor : 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 organisms themselves.

Growth rate : The rate at which growth occurs, usually expressed as the generation time.

GTT : Glucose tolerance test.

GU : Genitourinary.

Guaiac : Used as a reagent to test for blood in the stool.

Guillain-Barre syndrome : Inflammation of the peripheral nerves leading to increasing weakness or paralysis; most often occurs in more distal areas before affecting portions of the body more proximally. Usually remists with resolution of the underlying disease.

Gymnothecium (pl. gymnothecia) : A cleistothecium-like ascocarp with loosely woven hyphae with asci loosely distributed throughout.

Gyn : Gynecology.