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Overexpression of sigC in the wild type

ABSTRACT: 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.

ORGANISM(S): Corynebacterium glutamicum Corynebacterium glutamicum R

PROVIDER: GSE72451 | GEO | 2016/08/22

SECONDARY ACCESSION(S): PRJNA294085

REPOSITORIES: GEO

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Project description:Hydrogen can be an important source of energy for chemolithotrophic acidophiles, especially in the deep terrestrial subsurface. Nevertheless, the current knowledge of microbial hydrogen utilization in acidic environments is minimal. A multi-omics analysis was applied on Acidithiobacillus ferrooxidans growing aerobically and anaerobically (with ferric iron) on hydrogen as an electron donor, and a respiratory model proposed from the results obtained. In this model, both [NiFe] hydrogenases, cytoplasmic uptake and membrane-bound respiratory, oxidize molecular hydrogen to two protons and two electrons. The electrons are used to reduce membrane-soluble ubiquinone to ubiquinol. Genetically associated [FeS]-binding proteins mediate electron relay from the hydrogenases to the ubiquinone pool. Under aerobic conditions, reduced ubiquinol transfers electrons to either cytochrome aa3 oxidase via cytochrome bc1 complex and cytochrome c4 or the alternate directly to cytochrome bd oxidase, resulting in proton efflux together with the reduction of molecular oxygen to water. Under anaerobic conditions, reduced ubiquinol transfers electrons to outer membrane cytochrome c (ferric iron reductase) via cytochrome bc1 complex and a cascade of electron transporters (cytochrome c4, cytochrome c552, rusticyanin, and high potential iron-sulfur protein), resulting in proton efflux together with the reduction of ferric iron to ferrous iron. The proton gradient generated by molecular hydrogen oxidation maintains the membrane potential and allows the generation of ATP via ATP synthase and NADH via NADH-ubiquinone oxidoreductase. To a lesser extent, NADH can also be generated by another bidirectional cytoplasmic hydrogenase. ATP and NADH are further utilized in the Calvin–Benson–Bassham cycle for inorganic carbon uptake and assimilation. These results further clarify the role of extremophiles in biogeochemical processes and their impact on the composition and features of the deep terrestrial subsurface from the distant past to the present.

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Overexpression of sigC in the wild type

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