gram-negative

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gram-negative

 [gram-neg´ah-tiv]
losing the stain or decolorized by alcohol in Gram's method of staining; see Gram stain. This is a primary characteristic of bacteria having a cell wall composed of a thin layer of peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide.

gram-neg·a·tive

(gram-neg'ă-tiv), In this expression gram begins with lowercase g but Gram stain takes an uppercase G.
Refers to the inability of a type of bacterium to resist decolorization with alcohol after being treated with crystal violet. However, following decolorization, these bacteria can be readily counterstained with safranin, imparting a pink or red color to them when viewed by light microscopy. This reaction is usually an indication that the outer structure of the bacterium consists of a cytoplasmic (inner) membrane surrounded by a relatively thin peptidoglycan layer, which in turn is surrounded by an outer membrane. See: Gram stain.

gram-negative

/gram-neg·a·tive/ (-neg´ah-tiv) losing the stain or decolorized by alcohol in Gram's method of staining, characteristic of bacteria having a cell wall surface more complex in chemical composition than the gram-positive bacteria.

gram-negative

or

Gram-negative

(grăm′nĕg′ə-tĭv)
adj.
Of, relating to, or being a bacterium that does not retain the violet stain used in the Gram stain method.

gram-negative

Etymology: Hans C.J. Gram, Danish physician, 1853-1938; L, negare, to say no
having the pink color of the counterstain used in Gram's method of staining microorganisms. This property is a primary method of characterizing organisms in microbiology. Some of the most common gram-negative pathogenic bacteria are Bacteroides fragilis, Brucella abortus, Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Neisseria gonorrhoeae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae, and Yersinia pestis.

gram-neg·a·tive

(gram-neg'ă-tiv)
Refers to the inability of a bacterium to resist decolorization with alcohol after being treated with Gram crystal violet. However, following decolorization, these bacteria can be readily counterstained with safranin, imparting a pink or red color to the bacterium when viewed by light microscopy.
See: Gram stain

Gram-negative

see GRAM'S STAIN.

Gram-negative

Refers to the property of many bacteria that causes them to not take up color with Gram's stain, a method which is used to identify bacteria. Gram-positive bacteria which take up the stain turn purple, while Gram-negative bacteria which do not take up the stain turn red.

gram-neg·a·tive

(gram-neg'ă-tiv)
Refers to the inability of a type of bacterium to resist decolorization with alcohol after being treated with crystal violet.

gram-negative

said of bacteria that are decolorized by alcohol in Gram's method of staining (see gram's stain), and are thus stained only with the counter stain (usually red). Gram-negative bacteria have a much thinner layer of peptidoglycan in the cell wall than Gram-positive bacteria.
References in periodicals archive ?
The percentage distribution of the number of the Gram-negative bacteria from gills and intestine.
In order to generate a set of rules that could be used to make antibiotics that will target Gram-negative bacteria, the team screened 180 different chemicals for their ability to penetrate E.
Gram-positive and gram-negative bacteria differ in their sensitivity to antibiotics.
Although most clinicians can agree that most bacteria identified on Gram's stain should be gram positive, there is a difference of opinion as to what percentage of gram-negative bacteria is acceptable.
In addition, 10 clinical isolates of MRSA and 13 clinical isolates of Gram-negative bacteria were included in this study.
Specifically disrupts lipids found in Gram-negative bacteria membranes while not affecting membranes in eukaryotic cells--cells with the nucleus and other structures enclosed in separate membranes found in mammals and other nonmicrobial life.
Pattern of bacterial isolates and frequency of ESBL gram-negative bacteria from wound culture is shown in Table-I.
The evidence supports the theory that limiting the use of specific antimicrobial drugs will reduce the prevalences of resistant gram-negative bacteria and CDAD.
Goodlett is an associate professor in the Medicinal Chemistry Department at the University of Washington, where he directs mass spectrometry cores for biodefense research in gram-negative bacteria and ecogenetics and environmental health.
Initial antibacterial testing results indicate that the natural product is effective against gram-positive bacteria and not gram-negative bacteria.
Durner and his colleagues tested another group of telltale molecules, the lipopolysaccharides from the cell surfaces of gram-negative bacteria.
Lipopolysaccharide is a component of the outer membrane of gram-negative bacteria and is the principal mediator of gram-negative bacterial toxicity to animals.

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