Gram-negative

[ gram-neg-uh-tiv ]

adjective

, (often lowercase)

1. (of bacteria) not retaining the violet dye when stained by Gram's method.

Gram-negative

adjective

1. designating bacteria that fail to retain the violet stain in Gram's method

gram-negative

1. Relating to a group of bacteria that do not change color when subjected to the laboratory staining method known as Gram's method or Gram's stain. Gram-negative bacteria have relatively thin cell walls and are generally resistant to the effects of antibiotics or the actions of the body's immune cells. Gram-negative bacteria include E. coli and the bacteria that cause gonorrhea, typhoid fever, rickettsial fever, cholera, syphilis, plague, and Lyme disease.
2. Compare gram-positive

Word History and Origins

Origin of Gram-negative¹

First recorded in 1905–10; Gram's method

Example Sentences

Gram-negative bacteria have a double layer of protection, making them more difficult to kill, Muñoz said.

From Science Daily

Fusobacterium is a Gram-negative microbe found in the GI tract and the oral cavity, and previous studies have connected it to the development of CRC.

From Science Daily

A new medicine capable of combating Gram-negative bacteria, a particularly hardy type of bug with inner and outer membranes that antibiotics struggle to cross, hasn’t hit the market in 50 years.

From Los Angeles Times

Encased in both an inner and outer membrane that antibiotics struggle to cross, Gram-negative bacteria are resistant to most currently available therapies.

From Los Angeles Times

Gram-negative bacteria differ from gram-positive in the composition of their cell walls.

From Science Daily