Regulatory interactions among the cya, crp and pts gene products in Salmonella typhimurium.

A well-characterized set of pts deletion mutants of Salmonella typhimurium were used to re-evaluate the purported role of the PTS in the inducer exclusion process and in regulation cAMP synthesis. During the course of these studies a class of secondary mutations was isolated which suppress the inhibition of cAMP synthesis caused by pts mutations. These suppressor mutations were traced to the crp locus and tentatively designated as acr (adenylate cyclase regulation) mutations. A new model is proposed in which CRP rather than adenylate cyclase is believed to be the central regulatory element in the catabolite repression phenomenon.