title: Apparent redundancy of electron transfer pathways via bc(1) complexes and terminal oxidases in the extremophilic chemolithoautotrophic Acidithiobacillus ferrooxidans.
abstract: Acidithiobacillus ferrooxidans is an acidophilic chemolithoautotrophic bacterium that can grow in the presence of either the weak reductant Fe(2+), or reducing sulfur compounds that provide more energy for growth than Fe(2+). We have previously shown that the uphill electron transfer pathway between Fe(2+) and NAD(+) involved a bc(1) complex that functions only in the reverse direction [J. Bacteriol. 182, (2000) 3602]. In the present work, we demonstrate both the existence of a bc(1) complex functioning in the forward direction, expressed when the cells are grown on sulfur, and the presence of two terminal oxidases, a bd and a ba(3) type oxidase expressed more in sulfur than in iron-grown cells, besides the cytochrome aa(3) that was found to be expressed only in iron-grown cells. Sulfur-grown cells exhibit a branching point for electron flow at the level of the quinol pool leading on the one hand to a bd type oxidase, and on the other hand to a bc(1)-->ba(3) pathway. We have also demonstrated the presence in the genome of transcriptionally active genes potentially encoding the subunits of a bo(3) type oxidase. A scheme for the electron transfer chains has been established that shows the existence of multiple respiratory routes to a single electron acceptor O(2). Possible reasons for these apparently redundant pathways are discussed.
authors.affiliation: Laboratoire de Bioénergétique et Ingénierie des Protéines, IBSM, CNRS, 31 Chemin J. Aiguier 13402 Marseille Cedex 20, France.
authors.forename: G
authors.initials: G
authors.lastname: Brasseur
authors.forename: G
authors.initials: G
authors.lastname: Levican
authors.forename: V
authors.initials: V
authors.lastname: Bonnefoy
authors.forename: D
authors.initials: D
authors.lastname: Holmes
authors.forename: E
authors.initials: E
authors.lastname: Jedlicki
authors.forename: D
authors.initials: D
authors.lastname: Lemesle-Meunier
mesh_terms: D042763:Acidithiobacillus / Q000378:metabolism*; D000332:Aerobiosis; D055592:Biophysical Phenomena; D001703:Biophysics; D019295:Computational Biology; D003573:Cytochrome b Group / Q000737:chemistry / Q000235:genetics; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry / Q000378:metabolism*; D016680:Genome, Bacterial; D007501:Iron / Q000378:metabolism; D008954:Models, Biological; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D013379:Substrate Specificity; D013455:Sulfur / Q000378:metabolism
chemical_list: D003573:Cytochrome b Group; D013455:Sulfur; D007501:Iron; D010088:Oxidoreductases; D014450:Electron Transport Complex III; D010100:Oxygen