dgg32
iron_oxidation
Bonnefoy 2012 Genomic insights into microbial iron oxidation and iron uptake strategies in extremely acidic environments
Model of the oxidation of Fe(II) in At. ferrooxidans based on biochemical, molecular genetics, bioenergetic, bioinformatic and functional genomics evidence. A redox tower has been placed below the model to facilitate comparison of the redox potentials of some of the reactions. Electrons extracted from the oxidation of Fe(II) by the outer membrane embedded cytochrome c Cyc2 are passed to the periplasmic copper protein rusticyanin (R). From rusticyanin, the electrons can take a download pathway to reduce O2 to water (solid arrow) passing through the cytochrome c4 Cyc1 and the aa3 type cytochrome oxidase complex or an uphill pathway (dotted arrow) to the NADH1 complex via the cytochrome c4 CycA1, the bc1 complex and membrane-associated quinones. The energy to push electrons uphill against this thermodynamically unfavourable gradient is postulated to come from the influx of protons (solid arrows) generated by the proton motive force across the inner membrane resulting from the difference in proton concentration inside the cell (pH 6.5) and outside (pH 2). This uphill pathway is similar in many respects to the pathways taken by electrons and protons in mitochondrial and prokaryotic oxidative phosphorylation, only in reverse. The figure also shows the influx of protons through the ATP synthetase complex (ATPase) driving the biosynthesis of ATP. These protons and also those that enter the cell to drive electrons uphill are postulated to be consumed, at least in part, by the reduction of O2 to water using electrons derived from the oxidation of Fe(II) via the downhill pathway. Abbreviations used: R, rusticyanin; OM, outer membrane; IM, inner membrane. * = values of E•0 for the Fe(III)/Fe(II) and 1/2 O2/H2O couples for pH 2 (Ferguson and Ingledew, 2008). Figure reproduced with modifications from Quatrini and colleagues (2009).
iron_oxidation
Bonnefoy 2012 Genomic insights into microbial iron oxidation and iron uptake strategies in extremely acidic environments
Model of the oxidation of Fe(II) in At. ferrooxidans based on biochemical, molecular genetics, bioenergetic, bioinformatic and functional genomics evidence. A redox tower has been placed below the model to facilitate comparison of the redox potentials of some of the reactions. Electrons extracted from the oxidation of Fe(II) by the outer membrane embedded cytochrome c Cyc2 are passed to the periplasmic copper protein rusticyanin (R). From rusticyanin, the electrons can take a download pathway to reduce O2 to water (solid arrow) passing through the cytochrome c4 Cyc1 and the aa3 type cytochrome oxidase complex or an uphill pathway (dotted arrow) to the NADH1 complex via the cytochrome c4 CycA1, the bc1 complex and membrane-associated quinones. The energy to push electrons uphill against this thermodynamically unfavourable gradient is postulated to come from the influx of protons (solid arrows) generated by the proton motive force across the inner membrane resulting from the difference in proton concentration inside the cell (pH 6.5) and outside (pH 2). This uphill pathway is similar in many respects to the pathways taken by electrons and protons in mitochondrial and prokaryotic oxidative phosphorylation, only in reverse. The figure also shows the influx of protons through the ATP synthetase complex (ATPase) driving the biosynthesis of ATP. These protons and also those that enter the cell to drive electrons uphill are postulated to be consumed, at least in part, by the reduction of O2 to water using electrons derived from the oxidation of Fe(II) via the downhill pathway. Abbreviations used: R, rusticyanin; OM, outer membrane; IM, inner membrane. * = values of E•0 for the Fe(III)/Fe(II) and 1/2 O2/H2O couples for pH 2 (Ferguson and Ingledew, 2008). Figure reproduced with modifications from Quatrini and colleagues (2009).