GATE 2023 ES – Question 38
Consider I Bacteriophage is an anaerobic bacterium;II Male-specific phages infect via pili of other microorganisms including viruses;III Phages occur in human/animal excreta;IV Phages cannot indicate bacteria. Choose the correct option.
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Correct answer: (D) III, IV both correct
Explanation
The official answer is **D**,accepting III and IV. III is correct:phages occur in fecal material. IV is overbroad:phages infect bacterial hosts and coliphages are used as indicators in water-quality assessment, although their use may target fecal contamination/viral behavior rather than directly enumerate all bacteria. I is false because phages are viruses, not bacteria; II wrongly extends a bacterial-pilus infection mechanism to viruses. The key is preserved while this indicator-wording problem is explicit.