Which statement is true about obligate anaerobes?

Which statement is true about obligate anaerobes?

• A. They require oxygen to grow
• B. They can grow only in oxygen-free environments
• C. They can grow with or without oxygen
• D. They cannot tolerate oxygen and must be cultured in oxygen-free environments

Answer: (D)

Obligate anaerobes cannot survive in the presence of oxygen because they lack the protective enzymes (like catalase and superoxide dismutase) that detoxify reactive oxygen species produced when oxygen is present. This makes oxygen toxic to them, so they must be grown under strictly anaerobic, oxygen-free conditions. That’s why the statement describing them as unable to tolerate oxygen and requiring an oxygen-free environment best captures their biology. In practice, labs culture these organisms in anaerobic chambers or jars with reducing agents to remove residual oxygen.

Obligate anaerobes cannot survive in the presence of oxygen because they lack the protective enzymes (like catalase and superoxide dismutase) that detoxify reactive oxygen species produced when oxygen is present. This makes oxygen toxic to them, so they must be grown under strictly anaerobic, oxygen-free conditions. That’s why the statement describing them as unable to tolerate oxygen and requiring an oxygen-free environment best captures their biology. In practice, labs culture these organisms in anaerobic chambers or jars with reducing agents to remove residual oxygen.