This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Corynebacterium, Subject name: Microbiology
All are true regarding diphtheria toxin EXCEPT : 
Select and explain. 
A. Toxin blocks elongation of protein, B. Beta lysogenic strain produces toxin, C. Iron is critical for toxin production, D. Toxin is necessary for local wound production
D: Toxin is necessary for local wound production
Answer: D: Toxin is necessary for local wound production 
Explanation: Ans. is 'd' i.e Toxin is necessary for local wound production " Corynebacterium Diptheria does not need to be toxigenic to establish localized infection, In the nasopharynx or skin, but non toxigenic strains do not yield the localized or systemic effect" - JawetzWhat I get from the above lines is that Non toxigenic strains of C diphtheriae can cause local wound production or infection but they will not be able to produce clinical effects.C.Diphtheriae produces a heat labile exotoxinThe production of this toxin depends largely on the concentration of Iron. Toxin production is optimal at 0.14mg/ml and is suppressed at 0.5 mg/mlThe toxigenicity of the Diptheria Bacillus depends on the presence in it of corynephages (tox+ i.e. toxigenic).Non toxigenic strains may be rendered toxigenic by infecting them with Beta phage or some other tox* phage.This is known as lysogenic conversion or phage conversion.Toxin inhibits the protein synthesis by inhibiting the polypeptide chain elongation.