Figure 1

Model of the iron oxidation electron transport pathway of At. ferrooxidans based partly on references [10, 75]. Electrons are transferred from the membrane-located cytochrome c 2 [97] to rusticyanin and then along one of two paths. The downhill path is via cytochrome c₄ (Cyt1) to cytochrome aa₃ [2] or the uphill, reverse electron transport path via cytochrome c₄ (CytA1) to a bc₁ I complex and a NADH-Q oxidoreductase [28]. At. ferrooxidans has up to twelve cytochromes c [98] and a variety of cytochrome oxidases some of which appear to play different roles depending on whether iron or sulfur is being oxidized [10]. The NADH is responsible for mercury reduction using a MerA mercuric reductase and the cytochrome aa₃ is required to reduce mercury via the unique iron dependent mechanism discovered in At. ferrooxidans [84].