Gram-negative bacteria
Gram-negative bacteria
Gram-negative bacteria (pronunciation: /ɡræmˈnɛɡətɪv bækˈtɪəriə/) are a group of bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell walls which are thin but complex in structure.
Etymology
The term "Gram-negative" is named after the Danish bacteriologist Hans Christian Gram, who developed the Gram staining technique in 1884. The "-negative" part of the term refers to the fact that these types of bacteria do not retain the crystal violet stain during the Gram staining process.
Characteristics
Gram-negative bacteria have a characteristic cell wall structure. The outer membrane of these bacteria contains lipopolysaccharide (LPS), which can trigger a strong immune response in animals. The cell wall also contains peptidoglycan, but much less than the Gram-positive bacteria. This makes the cell wall thinner and more permeable, which is why Gram-negative bacteria do not retain the crystal violet stain.
Related Terms
- Gram staining: A method of differentiating bacterial species into two large groups (Gram-positive and Gram-negative).
- Gram-positive bacteria: Bacteria that retain the crystal violet stain used in the Gram staining method.
- Lipopolysaccharide: A large molecule consisting of a lipid and a polysaccharide, found in the outer membrane of Gram-negative bacteria.
- Peptidoglycan: A polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria.
See Also
External links
- Medical encyclopedia article on Gram-negative bacteria
- Wikipedia's article - Gram-negative bacteria
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