Gram-negative bacteria

Gram-negative bacteria are a group of bacteria that are classified by the color they turn after a chemical process called Gram staining is used on them. Gram-negative bacteria are more resistant to antibiotics than Gram-positive bacteria because they have a protective outer layer that prevents the antibiotics from reaching their target.

Characteristics

Gram-negative bacteria have a characteristic cell envelope structure. The cell wall is thin and is located between the cell membrane and an additional outer membrane. The outer membrane of Gram-negative bacteria is often associated with pathogenicity as it contains lipopolysaccharides (LPS) that can act as endotoxins.

Classification

Gram-negative bacteria include a wide variety of species. Some are pathogens, causing diseases in humans and other animals, while others are important in environmental or industrial contexts. They can be classified according to their shape into cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped).

Pathogenicity

Many Gram-negative bacteria are pathogenic, meaning they can cause disease. This is often due to the presence of LPS in their outer membrane, which can trigger a strong immune response in animals. Some examples of diseases caused by Gram-negative bacteria include pneumonia, meningitis, and gonorrhea.

Treatment

Treatment of infections caused by Gram-negative bacteria can be challenging due to their inherent resistance to many antibiotics. This resistance is due to the presence of an outer membrane that acts as a barrier to many drugs, as well as the ability of these bacteria to pump out drugs that do penetrate the outer membrane.

See also

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

• Pseudomonas aeruginosa under Gram stain
  Pseudomonas aeruginosa under Gram stain
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  Structure of Gram-negative cell wall
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  Comparison of Gram-positive and Gram-negative cell walls
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  Diagnostic algorithm of possible bacterial infection