gram-negative
UK[ˌɡræm ˈneɡətɪv]US[ˌɡræm ˈneɡətɪv]
adj
(of a bacterium) not retaining the violet stain used in Gram's method of staining, typically having a thinner cell wall.
Morpheme Breakdown
gram
negative
gram
name
negative
state
Etymology
The term is a scientific eponym combined with a descriptive adjective. It originates from the Gram stain, a differential staining technique developed by Hans Christian Gram in 1884 to classify bacteria. The suffix "negative" is applied in its standard scientific sense of "not showing a specified reaction or characteristic." Thus, "gram-negative" literally means "negative for the Gram stain," describing bacteria whose cell wall structure does not retain the crystal violet dye, a key diagnostic feature in microbiology.
Analysis
Structure: gram (name) + negative (state)
- gram: From the surname of the Danish bacteriologist Hans Christian Gram (1853–1938). It functions as a proper noun attributive, naming the specific staining method.
- negative: From Latin negativus, meaning "that denies, negative." It functions as an adjective indicating the absence or opposite of a quality (here, the absence of stain retention).
Examples
Gram-negative bacteria, such as E. coli, are often responsible for infections in the intestinal tract.
The outer membrane of gram-negative cells provides an additional barrier against certain antibiotics.
Laboratory tests confirmed the presence of a gram-negative rod in the blood culture.