title: The cytochrome bd oxidase of Escherichia coli prevents respiratory inhibition by endogenous and exogenous hydrogen sulfide.
abstract: When sulfur compounds are scarce or difficult to process, Escherichia coli adapts by inducing the high-level expression of sulfur-compound importers. If cystine then becomes available, the cystine is rapidly overimported and reduced, leading to a burgeoning pool of intracellular cysteine. Most of the excess cysteine is exported, but some is adventitiously degraded, with the consequent release of sulfide. Sulfide is a potent ligand of copper and heme moieties, raising the prospect that it interferes with enzymes. We observed that when cystine was provided and sulfide levels rose, E. coli became strictly dependent upon cytochrome bd oxidase for continued respiration. Inspection revealed that low-micromolar levels of sulfide inhibited the proton-pumping cytochrome bo oxidase that is regarded as the primary respiratory oxidase. In the absence of the back-up cytochrome bd oxidase, growth failed. Exogenous sulfide elicited the same effect. The potency of sulfide was enhanced when oxygen concentrations were low. Natural oxic-anoxic interfaces are often sulfidic, including the intestinal environment where E. coli dwells. We propose that the sulfide resistance of the cytochrome bd oxidase is a key trait that permits respiration in such habitats.
authors.affiliation: Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: Sergey
authors.initials: S
authors.lastname: Korshunov
authors.affiliation: Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: Karin R C
authors.initials: KR
authors.lastname: Imlay
authors.affiliation: Department of Microbiology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Imlay
mesh_terms: D003573:Cytochrome b Group; D003580:Cytochromes / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006862:Hydrogen Sulfide / Q000378:metabolism* / Q000494:pharmacology*; D010088:Oxidoreductases / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli; C038862:cytochrome o oxidase; D003576:Electron Transport Complex IV; D010100:Oxygen; D006862:Hydrogen Sulfide