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• Gram-negative
  Gram-negative

  adjective

  (of bacteria) not retaining the violet dye when stained by Gram's method.
• gram-negative
  gram-negative

  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.

Gram-negative

American  

[gram-neg-uh-tiv] / ˈgræmˈnɛg ə tɪv /

adjective

(often lowercase)

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

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Gram-negative British  

adjective

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

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gram-negative Scientific  

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

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Etymology

Origin of Gram-negative

First recorded in 1905–10; see origin at Gram's method

Example Sentences

See Examples For:

Gram-negative gram-negative

This data will then be fed into the AI so it can learn what it takes for an antibiotic to persist inside a Gram-negative bacterium.

From BBC ● Nov. 18, 2025

He will be targeting AI at a tricky group of infections, called Gram-negative bacteria, that includes well known bugs such as E. coli and Klebsiella pneumoniae.

From BBC ● Nov. 18, 2025

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 ● Feb. 15, 2024

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

From Science Daily ● Nov. 22, 2023

All strains show tendency to chain formation, some being arranged 116in chains of six to twenty-five segments, which may contain both Gram-positive and Gram-negative individuals.

From The Bacillus of Long Life a manual of the preparation and souring of milk for dietary purposes, together with and historical account of the use of fermente by Loudon Douglas

Both pathogens studied are gram-negative bacteria with shared characteristics, but also notable differences.

From Science Daily ● Mar. 7, 2024

Subsequent cryo-electron tomographic analysis visualized the step-by-step details of how this secretion system exports cellular contents via a previously unknown lytic mode of action that overcomes the three barriers surrounding gram-negative bacteria.

From Science Daily ● Jan. 19, 2024

Methicillin-resistant Staphylococcus aureus and drug-resistant tuberculosis raised alarms; additionally, so-called gram-negative bacteria were proving evermore resistant to antibiotics.

From Washington Post ● Jan. 18, 2023

In gram-negative bacteria, the proton gradient that supplies the free energy to convert ADP into ATP is established across the inner membrane.

From Textbooks ● Jun. 9, 2022

Cells believe that it signifies the presence of gram-negative bacteria, and they will stop at nothing to avoid this threat.

From "The Lives of a Cell" by Lewis Thomas