Question

Mutant strains of Vibrio cholerae can be isolated that fail to produce cholera. As a microbiologist you may postulate that the defect is related to the following CA. Vibrio cholerae is in the lytic phase CB. Vibrio cholerae is in the lysogenic phase CC. Lack of repressor in the Vibrio cholerae D. Mutations in the phages genes

Answer 1

Answer:   “ D ” mutation in phage genes

Vibrio cholerae is a Gram negative organism and is a causative agent of cholera. The organism requires 2 regulated factors for full virulence. The 2 factors are as follows

• Cholera toxin (CT)   it is a Enterotoxin
• Toxin –co regulated pili (TCP) it is surface organelles required for colonization of Vibrio.

The structural genes required for CT are encoded by a Filamentous bacteriophage which is incorporated in genome of Vibrio Cholerae.( this is lysogenic state )

So if there is mutation in phage related genes, which is integrated in to the Vibrio genome, resulting in lack of ability to produce the enterotoxin. This would results in loss of pathogenicity of Vibrio .