A strain of Corynebacterium diphtheriae isolated from a healthy carrier is nontoxigenic on Elek's test. After infection with bacteriophage beta in vitro, the same strain produces diphtheria toxin and tests positive. What is this phenomenon called?
- A Generalized transduction
- B Transformation with naked phage DNA
- C Phage (lysogenic) conversion ✓
- D Transfer of the tox gene by conjugation
Correct answer: C. Phage (lysogenic) conversion
Explanation
The structural gene for diphtheria toxin resides on the genome of corynephage beta, so only strains lysogenised by this temperate phage become toxigenic. Acquisition of new phenotypic traits through expression of prophage genes is termed phage conversion or lysogenic conversion. Generalized transduction involves accidental packaging of random host chromosomal DNA rather than expression of a resident prophage gene, transformation requires naked extracellular DNA, and C. diphtheriae does not exchange this trait by conjugation.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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