Which organism type does not use oxygen but tolerates it?

• A. Aerotolerant organisms
• B. Aerobes
• C. Anaerobes
• D. Facultative anaerobes

Answer: (A)

When bacteria are grouped by how they interact with oxygen, you’ll see several patterns: some need oxygen to grow, some are poisoned by it, some can use it if it’s available, and a special group doesn’t use oxygen for metabolism but can survive in its presence. The correct type here is the one that does not use oxygen for energy but can tolerate its presence. These organisms rely on fermentation rather than aerobic respiration, so oxygen doesn’t help them grow. However, they keep their cells safe in oxygen-rich environments because they possess enzymes that detoxify reactive oxygen species, such as superoxide dismutase and catalase. That combination—no use of oxygen for metabolism, but ability to survive in its presence—defines aerotolerant organisms.