This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
What genetic pecularity is there in pathogenic/ toxigenic strain of corynebacterium diphtheriae but not in nonpathogenic strain - 
Select and explain. 
A. Presence of R-factor, B. Presence of gene, C. Integrated temperate phage, D. Presence of MDR gene
C: Integrated temperate phage
Answer: C: Integrated temperate phage 
Explanation: Ans. is 'c' i.e., Integrated temperate phage The toxigenicity of the diphtheria bacilli depends on the presence in it of corynephages (tox +). Nontoxigenic strains may be rendered toxigenic by infecting them with beta phage or some other larger phage.This is known as lysogenic conversion or phage conversion.