C. diphtheriae was the first bacterium for which the symptoms of disease could be explained entirely by the action of a single secreted protein, DT. DT is produced when iron levels are low. Describe...

C. diphtheriae was the first bacterium for which the symptoms of disease could be explained entirely by the action of a single secreted protein, DT. DT is produced when iron levels are low. Describe in detail how you would determine if the dtxR gene encodes a transcriptional activator or repressor of DT gene (tox) expression under low-iron conditions.