True about corynebacterium diptheria includes all of the following except :: (A) Deep invasion is not seen, (B) Elek’s test is done for toxigenicity, (C) Metachromatic granules are seen, (D) Toxigenicity is mediated by chromosomal change
Answer is D. “Corynebacteriophage beta carries the structural gene (tox + ) encoding diptheria toxin and a family of closely related corynebacteriophage are responsible for toxigenic conversion of tox – C.diptheria to tox + phenotype.”

Elek’s gel precipitation test is in vitro test for toxin detection.