Gram-negative bacteria
Gram-negative bacteria are
Within this category, notable species include the
Several
Characteristics
Conventional gram-negative (LPS-diderm) bacteria display the following characteristics:[citation needed]
- An inner cell membrane is present (cytoplasmic)
- A thin peptidoglycan layer is present (this is much thicker in gram-positive bacteria)
- Has O antigen) in its outer leaflet and phospholipidsin the inner leaflet
- Porins exist in the outer membrane, which act like pores for particular molecules
- Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel-like substance called periplasm
- The S-layer is directly attached to the outer membrane rather than to the peptidoglycan
- If present, flagellahave four supporting rings instead of two
- Teichoic acids or lipoteichoic acids are absent
- Lipoproteins are attached to the polysaccharide backbone
- Some contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond
- Most, with few exceptions, do not form spores
Classification
Along with cell shape, Gram staining is a rapid diagnostic tool and once was used to group species at the subdivision of Bacteria. Historically, the kingdom Monera was divided into four divisions based on Gram staining: Firmacutes (+), Gracillicutes (−), Mollicutes (0) and Mendocutes (var.).[3] Since 1987, the
Taxonomy
This section may be too technical for most readers to understand.(March 2014) |
It has been suggested that this section be split out into another article titled Gram stain. (Discuss) (November 2023) |
Bacteria are traditionally classified based on their
Of these two structurally distinct groups of
The conventional LPS-diderm group of gram-negative bacteria (e.g.,
Example species
The
Medically-relevant gram-negative
Medically relevant gram-negative
Gram-negative bacteria associated with
Bacterial transformation
Transformation is one of three processes for horizontal gene transfer, in which exogenous genetic material passes from one bacterium to another, the other two being conjugation (transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a bacteriophage virus into the host bacterium).[18][19] In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium.[18]
As of 2014 about 80 species of bacteria were known to be capable of transformation, about evenly divided between
Role in disease
One of the several unique characteristics of gram-negative bacteria is the structure of the
The outer membrane protects the bacteria from several
Orthographic note
The adjectives gram-positive and gram-negative derive from the surname of
See also
References
- This article incorporates NCBI. Archived from the originalon 2009-12-08.
Notes
- ^ from the original on 2021-07-06. Retrieved 2021-08-18.
- ^ from the original on 2022-04-13. Retrieved 2021-05-12.
- .
- PMID 2439888.
- PMID 16834776.
- ^ PMID 9841678.
- ^ (PDF) from the original on 2018-07-20. Retrieved 2017-10-24.
- ^ PMID 19299134.
- ^ PMID 20637628.
- ^ PMID 9723910.
- ^ PMID 21717204.
- ^ PMID 19667386.
- PMID 21413290, retrieved 2024-03-28
- PMID 30026943.
- ^ "Vaccine Preventable Diseases Surveillance Manual". CDC. April 3, 2018. Retrieved January 26, 2024.
- PMID 11781271.
- ^ "For Clinicians: Haemophilus influenzae". CDC. February 13, 2018. Retrieved January 26, 2024.
- ^ S2CID 23559881.
- PMID 36838287.
- ^ PMID 22928673.
- ^ Glück, Thomas (12 December 2003). "Gram-Negative Bacteria and Broad-Spectrum Antibiotics: Good News Except for Fluoroquinolones". www.jwatch.org. NEJM Journal Watch. Archived from the original on 10 March 2018. Retrieved 10 March 2018.
- ^ "Preferred Usage - Emerging Infectious Disease journal - CDC". CDC.gov. Centers for Disease Control and Prevention. Archived from the original on 2018-01-29. Retrieved 2018-03-04.