Gram-negative

Gram-negative bacteria 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 envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.

Characteristics

Gram-negative bacteria are distinguished by the structure of their cell wall. The cell wall is thinner than that of Gram-positive bacteria, and it is located between two membranes, the inner or cytoplasmic membrane and the outer membrane. The space between these two membranes is known as the periplasmic space.

Pathogenesis

Many species of Gram-negative bacteria are pathogenic, meaning they can cause disease in the host organism. This pathogenic capability is usually associated with certain components of the Gram-negative cell wall, in particular the lipopolysaccharide (also known as LPS or endotoxin) layer. In humans, LPS triggers an immune response characterized by inflammation, fever, and blood clotting.

Examples

Examples of Gram-negative bacteria include Escherichia coli, Salmonella, Proteus, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Neisseria meningitidis, Moraxella catarrhalis, Helicobacter pylori, and many others.

Treatment

The treatment of Gram-negative bacterial infections often involves antibiotics. However, the effectiveness of these drugs is decreasing due to the increasing prevalence of antibiotic resistance among Gram-negative bacteria.

See also

• Gram-positive bacteria
• Bacterial cell structure
• Antibiotic resistance

Gram-negative Resources
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