Anaerobe

Anaerobe

An anaerobe is an organism that does not require oxygen for growth and may even die in its presence. Anaerobes can be classified into two main categories: obligate anaerobes and facultative anaerobes.

Types of Anaerobes

Obligate Anaerobes

Obligate anaerobes are organisms that cannot survive in the presence of oxygen. They rely on anaerobic respiration or fermentation to obtain energy. Examples include Clostridium species, which are known for causing diseases such as tetanus and botulism.

Facultative Anaerobes

Facultative anaerobes can grow in the presence or absence of oxygen. They can switch between aerobic respiration and anaerobic methods such as fermentation depending on the availability of oxygen. An example of a facultative anaerobe is Escherichia coli.

Metabolic Pathways

Anaerobes utilize various metabolic pathways to generate energy in the absence of oxygen. These include:

• Fermentation: A process that converts sugars to acids, gases, or alcohol. Lactic acid fermentation and alcoholic fermentation are common types.
• Anaerobic Respiration: Uses electron acceptors other than oxygen, such as nitrate, sulfate, or carbon dioxide.

Clinical Significance

Anaerobic bacteria are significant in both health and disease. They are part of the normal human microbiota, particularly in the gastrointestinal tract, oral cavity, and skin. However, they can also be pathogenic, causing infections such as:

• Bacterial vaginosis
• Periodontal disease
• Intra-abdominal infections

Laboratory Identification

Identifying anaerobes in the laboratory involves:

• Culture Techniques: Using anaerobic chambers or jars to create an oxygen-free environment.
• Biochemical Tests: To determine metabolic capabilities.
• Molecular Methods: Such as PCR for detecting specific anaerobic pathogens.

Treatment of Anaerobic Infections

Treatment often involves the use of antibiotics effective against anaerobes, such as:

• Metronidazole
• Clindamycin
• Carbapenems

See Also

• Aerobe
• Microaerophile
• Fermentation

References

• Madigan, M.T., Martinko, J.M., Bender, K.S., Buckley, D.H., & Stahl, D.A. (2014). Brock Biology of Microorganisms. Pearson.
• Brook, I. (2002). "Anaerobic infections in children". Pediatric Infectious Disease Journal.