Induction of the Operon Encoding the Quinol Oxidase Under Respiration-Inhibitory Conditions by the Major cAMP Receptor Protein MSMEG_6189 in .

The respiratory electron transport chain (ETC) of is terminated with two terminal oxidases, the cytochrome oxidase and the cytochrome quinol oxidase. The quinol oxidase with a higher binding affinity for O than the oxidase is known to play an important role in aerobic respiration under oxygen-limiting conditions. Using relevant () and () mutant strains of , we demonstrated that Crp1 plays a predominant role in induction of the operon under ETC-inhibitory conditions. Two Crp-binding sequences were identified upstream of the gene, both of which are necessary for induction of expression under ETC-inhibitory conditions. The intracellular level of cAMP in was found to be increased under ETC-inhibitory conditions. The gene was found to be negatively regulated by Crp1 and Crp2, which appears to lead to significantly low cellular abundance of Crp2 relative to Crp1 in . Our RNA sequencing analyses suggest that in addition to the SigF partner switching system, Crp1 is involved in induction of gene expression in exposed to ETC-inhibitory conditions.