Project description:Bacteria modify expression of different types of terminal oxidase in response to oxygen availability. Corynebacterium glutamicum, a facultative anaerobic bacterium in Actinobacteria, possesses aa3-type cytochrome c oxidase and cytochrome bd-type quinol oxidase, the latter of which is induced upon oxygen limitation. We report here that an extracytoplasmic function sigma factor, SigC, is unprecedentedly responsible for the regulation. Chromatin immunoprecipitation in conjunction with microarray (ChIP-chip) analysis detected eight SigC-binding regions in the genome, leading to identification of a consensus promoter sequence for SigC recognition. The promoter sequences were found upstream of genes for cytochrome bd, heme a synthesis enzymes, and uncharacterized membrane proteins, all of which were upregulated by sigC overexpression. In contrast, that found on the antisense strand upstream of an operon encoding the cytochrome bc1 complex conferred a SigC-dependent negative effect on the operon expression. The SigC regulon was induced by cytochrome aa3 deficiency without modification of expression of sigC itself, but not by deficiency of the bc1 complex. These findings suggest that SigC is activated in response to impairment of electron transfer via cytochrome aa3, not directly to shift in oxygen levels. Our results provide a novel paradigm for transcriptional regulation of the aerobic respiratory system in bacteria.
