Organisms that are indifferent to the presence of oxygen are…

• A. Aerotolerant anaerobes.
• B. Facultative anaerobes.
• C. Obligate aerobes.
• D. Microaerophiles.

Answer: (A)

Verified step by step guidance

1. Begin by understanding the definitions of each term related to oxygen tolerance in organisms.
2. Aerotolerant anaerobes are organisms that do not require oxygen for growth but can tolerate its presence. They perform anaerobic metabolism regardless of oxygen availability.
3. Facultative anaerobes can grow in both the presence and absence of oxygen. They use aerobic respiration when oxygen is available and switch to anaerobic metabolism when it is not.
4. Obligate aerobes require oxygen for survival and growth, as they rely on aerobic respiration.
5. Microaerophiles require oxygen but at lower concentrations than what is found in the atmosphere. They thrive in environments with reduced oxygen levels.