Gram-positive bacterium

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.

Classification

Gram-negative bacteria include a wide variety of species. Some are harmless, while others are pathogenic and can cause serious diseases. They are classified into several families, including Enterobacteriaceae, Pseudomonadaceae, and Neisseriaceae, among others.

Pathogenesis

Many Gram-negative bacteria are pathogenic, meaning they can cause disease in a host organism. These bacteria often produce endotoxins, which are toxins released when the bacteria die and their cell walls disintegrate. Endotoxins can trigger a strong immune response, leading to symptoms such as fever, inflammation, and shock.

Antibiotic Resistance

Gram-negative bacteria are often more resistant to antibiotics than Gram-positive bacteria. This is due to their outer membrane, which can block the entry of certain drugs. In addition, many Gram-negative bacteria have efflux pumps, which can expel drugs from the cell.

See Also

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

References

Gram-positive bacterium Resources
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