anaerobses

Anaerobes are microorganisms that do not require oxygen for growth, and many cannot tolerate it. In microbiology, the term covers obligate anaerobes, which are harmed or killed by oxygen; facultative anaerobes, which can grow with or without oxygen; and aerotolerant anaerobes, which do not use oxygen but tolerate its presence. Many obligate anaerobes lack enzymes such as catalase or superoxide dismutase that detoxify reactive oxygen species, making oxygen harmful to them.

Metabolism in anaerobes is based on fermentation or anaerobic respiration using alternative electron acceptors. Fermenters produce energy and a variety of end products such as organic acids, alcohols, and gases. Some anaerobes perform anaerobic respiration with electron acceptors like nitrate, sulfate, or carbon dioxide, enabling growth in environments devoid of oxygen.

Habitat and ecology: Anaerobes are abundant in soil, sediments, and the gastrointestinal tracts of animals, including humans. They play key roles in nutrient cycling and digestion, and contribute to the stability and function of various ecosystems. While many anaerobes are beneficial or harmless commensals, others can be opportunistic or true pathogens under certain conditions.

Clinical relevance: Anaerobic bacteria are common causes of infections that occur in low-oxygen environments, such as deep wound infections, intra-abdominal infections, and periodontal diseases. Clostridium species are associated with gas gangrene and botulism, while Bacteroides fragilis group organisms are frequent culprits in intra-abdominal infections. Because many anaerobes are slow-growing and sensitive to oxygen, they can be difficult to culture and study.

Detection and treatment: Laboratory identification relies on anaerobic culture in specialized facilities or molecular methods. Treatment often includes antibiotics such as metronidazole, beta-lactam/beta-lactamase inhibitor combinations, carbapenems, or clindamycin, and may involve surgical management in severe infections. Prevention emphasizes proper infection control and judicious antibiotic use to preserve beneficial anaerobic microbes in the microbiome.