Which statement defines an aerobe?

• A. Bacteria that grows in the presence of oxygen.
• B. Bacteria that grows without oxygen.
• C. Bacteria that requires oxygen to survive.
• D. Bacteria that can survive without oxygen but prefers oxygen.

Answer: (A)

Oxygen availability defines how these microorganisms grow. An aerobe relies on oxygen for its metabolism, using aerobic respiration to generate energy, so it needs oxygen to grow. The statement describing bacteria that grows in the presence of oxygen matches this idea, because it highlights that oxygen supports their growth.

In contrast, organisms that grow without oxygen are anaerobes; those that can grow with or without oxygen (often preferring oxygen) describe facultative anaerobes and similar categories, which don’t fit the strict requirement that aerobes need oxygen for growth.