When Listeria monocytogenes is growing in the absence of oxygen, which metabolic process does it primarily use to generate ATP?

• A. Aerobic respiration
• B. Photosynthesis
• C. Chemolithotrophy
• D. Fermentation

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the metabolic options available to bacteria for ATP generation, including aerobic respiration, anaerobic respiration, fermentation, photosynthesis, and chemolithotrophy.
2. Step 2: Recognize that aerobic respiration requires oxygen as the final electron acceptor in the electron transport chain, so it cannot occur in the absence of oxygen.
3. Step 3: Recall that photosynthesis is a process used by certain bacteria and plants to convert light energy into chemical energy, which is unrelated to Listeria monocytogenes' metabolism.
4. Step 4: Know that chemolithotrophy involves the oxidation of inorganic molecules to generate energy, which is not the primary metabolic pathway for Listeria monocytogenes under anaerobic conditions.
5. Step 5: Conclude that in the absence of oxygen, Listeria monocytogenes primarily uses fermentation, a metabolic process that generates ATP by substrate-level phosphorylation without the need for oxygen.