True about corynebacterium diptheria includes all of the following except :
“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.
Deep invasion is not seen
Elek’s test is done for toxigenicity
Metachromatic granules are seen
Toxigenicity is mediated by chromosomal change