Diphtheria toxin is produced only by those strains of C. diphtheriae that are
All toxigenic strains of Corynebacterium diphtheriae are lysogenic for b-phage carrying the Tox gene, which codes for the toxin molecule. The expression of this gene is controlled by the metabolism of the host bacteria. The greatest amount of toxin is produced by bacteria grown on media containing very low amounts of iron.
Glucose fermenters
Sucrose fermenters
Lysogenic for b-prophage
Of the mitis strain
Bacteria