Fig. 5: Schematic metabolic model of D. alkaliphilus for sulfide oxidation with iron(iii) oxides based on comparative transcriptomics.
From: Microbial iron oxide respiration coupled to sulfide oxidation
D. alkaliphilus uses a reversed canonical dissimilatory sulfate reduction (Dsr) pathway to oxidize sulfide to sulfate (blue protein labels). Sulfide reacts with DsrC to form DsrC trisulfide (DCT), which is oxidized stepwise to sulfate via DsrAB, AprAB and Sat. The reducing equivalents are transferred to iron(iii) oxides via EET mechanisms (green protein labels) facilitated by MHCs. D. alkaliphilus also has genes encoding type IV pili (grey protein labels). The tight adhesion (Tad) pilus may drive the cell adherence to the surface of solid iron oxides and/or FeS. The transcription level of each gene during MISO is indicated by mean reads per kilobase of transcript per million mapped reads (RPKM) of four replicates corresponding to the colour in the legend. Blue and green dots show significantly increased gene transcription during sulfide/FeS oxidation and ferrihydrite reduction, respectively. The identifier, full name, RPKM, statistical significance of differential transcription and genomic arrangement for each gene are provided in Extended Data Fig. 3 and Supplementary Tables 2–5. Electron flow and proton translocation are indicated by red arrows. Black dotted arrows indicate putative sulfur redox reactions with unclear enzymology. APS, adenosine-5′-phosphosulfate, Qox, oxidized menaquinone; Qred, reduced menaquinone; FoxFeR, incubation of D. alkaliphilus under formate-oxidizing and ferrihydrite-reducing conditions; FeSoxFeR, incubation of D. alkaliphilus under FeS-oxidizing and ferrihydrite-reducing conditions; Sdisp, incubation of D. alkaliphilus under S(0) disproportionation conditions; SoxFeR, incubation of D. alkaliphilus under sulfide-oxidizing and ferrihydrite-reducing conditions; SoxNR, incubation of D. alkaliphilus under sulfide-oxidizing and nitrate-reducing conditions.
