New Insights Into Acidithiobacillus thiooxidans Sulfur Metabolism Through Coupled Gene Expression, Solution Chemistry, Microscopy, and Spectroscopy Analyses

Here, we experimentally expand understanding of the reactions and enzymes involved in Acidithiobacillus thiooxidans ATCC 19377 S(0) and [Formula: see text] metabolism by developing models that integrate gene expression analyzed by RNA-Seq, solution sulfur speciation, electron microscopy and spectroscopy. The A. thiooxidans [Formula: see text] metabolism model involves the conversion of [Formula: see text] to [Formula: see text] , S(0) and [Formula: see text] mediated by the sulfur oxidase complex (Sox), tetrathionate hydrolase (TetH), sulfide quinone reductase (Sqr), and heterodisulfate reductase (Hdr) proteins. These same proteins, with the addition of rhodanese (Rhd), were identified to convert S(0) to [Formula: see text] , [Formula: see text] and polythionates in the A. thiooxidans S(0) metabolism model. Our combined results shed light onto the important role specifically of TetH in [Formula: see text] metabolism. Also, we show that activity of Hdr proteins rather than Sdo are likely associated with S(0) oxidation. Finally, our data suggest that formation of intracellular [Formula: see text] is a critical step in S(0) metabolism, and that recycling of internally generated [Formula: see text] occurs, through comproportionating reactions that result in [Formula: see text]. Electron microscopy and spectroscopy confirmed intracellular production and storage of S(0) during growth on both S(0) and [Formula: see text] substrates.