Which term describes bacteria that can continue metabolism at low pH and produce acid?

• A. Non-acidogenic
• B. Alkaliphilic
• C. Acidogenic and aciduric
• D. Acidogenic only

Answer: (C)

This question tests the idea of bacteria that both produce acid and can keep functioning in acidic environments. Acidogenic means the organism generates acid from carbohydrate metabolism. Aciduric means it can survive and continue metabolic activity even when the pH drops, i.e., it tolerates and thrives in acid. To satisfy both conditions—continuing metabolism at low pH and producing acid—the organism must be both acidogenic and aciduric. The other terms describe only one aspect: non-acidogenic does not produce acid; alkaliphilic prefers high pH; acidogenic only produces acid but may not sustain activity as the environment becomes acidic. Therefore, acidogenic and aciduric best fits the description.