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. This process was developed by the Danish bacteriologist Hans Christian Gram, who divided bacteria into two groups - Gram-positive and Gram-negative.

Characteristics

Gram-negative bacteria are characterized by their cell walls, which are thin but complex. The cell wall contains a thin layer of peptidoglycan, a polymer consisting of sugars and amino acids, and an outer membrane. The outer membrane of Gram-negative bacteria is rich in lipopolysaccharides, which are complex lipid molecules that provide a barrier against certain antibiotics, dyes, and detergents.

Classification

Gram-negative bacteria include a wide variety of species, which can be classified based on their shape, metabolism, and other characteristics. Some of the major groups of Gram-negative bacteria include:

• Enterobacteriaceae, a large family that includes many common pathogens such as Escherichia coli and Salmonella.
• Pseudomonadaceae, a family of bacteria that are often found in soil and water, and include species that can cause disease in humans.
• Neisseriaceae, a family that includes the pathogens Neisseria gonorrhoeae, which causes gonorrhea, and Neisseria meningitidis, which causes meningitis.

Pathogenesis

Many Gram-negative bacteria are pathogenic, meaning they can cause disease. The lipopolysaccharides in their outer membrane can trigger a strong immune response in humans and other animals. This can lead to inflammation, fever, and other symptoms of infection. Some Gram-negative bacteria also produce exotoxins, which are toxic substances that can damage tissues or interfere with normal bodily functions.

Treatment

Treating infections caused by Gram-negative bacteria can be challenging, as these bacteria are often resistant to many common antibiotics. This resistance is due in part to the outer membrane, which can prevent drugs from reaching their target. However, certain antibiotics, such as aminoglycosides and quinolones, are effective against many Gram-negative bacteria.

See also

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

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