Granary weevil

Gram-positive bacteria are a group of bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories. This test is named after its inventor, Danish scientist Hans Christian Gram.

Characteristics

Gram-positive bacteria are characterized by having a thick peptidoglycan cell wall, which retains the violet crystal violet stain during the Gram staining procedure. This is in contrast to Gram-negative bacteria, which do not retain the crystal violet stain and instead take up the counterstain (red) in the Gram stain procedure.

Classification

Gram-positive bacteria are classified into two main groups, the Actinobacteria and the Firmicutes. The Actinobacteria include the genera Mycobacterium, Corynebacterium, Propionibacterium, and others. The Firmicutes include the genera Bacillus, Clostridium, Streptococcus, Staphylococcus, Enterococcus, and others.

Medical relevance

Many Gram-positive bacteria are pathogenic in humans and cause a variety of diseases. For example, Staphylococcus aureus can cause skin infections, pneumonia, and toxic shock syndrome. Streptococcus pyogenes can cause strep throat, skin infections, and rheumatic fever. Clostridium difficile can cause severe diarrhea and pseudomembranous colitis.

Treatment

Gram-positive bacteria are generally more susceptible to antibiotics than Gram-negative bacteria, because they do not have an outer cell membrane that can block the entry of the drugs. However, many Gram-positive bacteria have developed resistance to commonly used antibiotics, which is a major concern in healthcare.

See also

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

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