True about corynebacterium diptheriae is

Toxin production is also influenced by the concentration of iron in the medium. The optimum level of iron for toxin production is 0.1mg/ l. The concentration of 0.5 mg / l inhibits the formation of the toxin. Only virulent strain produce powerful exotoxin. It inhibits protein synthesis. It is heat liable. Incubation at 37deg C for 4-6 weeks conve toxin to toxoid. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 240