Which term describes bacteria that can grow both in the presence and absence of oxygen?

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

Answer: (A)

Verified step by step guidance

1. Understand the oxygen requirements of different types of bacteria: Obligate aerobes require oxygen to grow, obligate anaerobes cannot tolerate oxygen, microaerophiles require oxygen but at lower concentrations than atmospheric levels, and facultative anaerobes can grow with or without oxygen.
2. Recall that facultative anaerobes have metabolic flexibility, allowing them to switch between aerobic respiration when oxygen is present and anaerobic respiration or fermentation when it is absent.
3. Identify that the question asks for bacteria that can grow both in the presence and absence of oxygen, which matches the definition of facultative anaerobes.
4. Eliminate other options based on their oxygen requirements: obligate aerobes only grow with oxygen, obligate anaerobes only grow without oxygen, and microaerophiles require low oxygen levels but not complete absence.
5. Conclude that the correct term describing bacteria capable of growth in both conditions is facultative anaerobes.