<prompt> All are true regarding diphtheria toxin exceptToxins blocks elongation of proteinBeta lysogenic strain produces toxinIron is critical for toxin productionToxic is necessary for local wound infection  <response>: Virulent strains of diphtheria bacilli produce a very powerful exotoxin. The pathogenic effects of the bacillus are due to the toxin. Almost all strains of gravis and intermedius are toxigenic. The toxin is extremely potent and the lethal dose for a 250 g guinea pig is 0.0001g. The toxin has a special affinity for ceain tissues such as the myocardium, adrenals and nerve endings. Reference: Textbook of Microbiology; Anathanarayan and panickers; 10th edition; Page no: 240 