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

Abstract

Here, we experimentally expand understanding of the reactions and enzymes involved in Acidithiobacillus thiooxidans ATCC 19377 S0 and (Formula presented.) metabolism by developing models that integrate gene expression analyzed by RNA-Seq, solution sulfur speciation, electron microscopy and spectroscopy. The A. thiooxidans (Formula presented.) metabolism model involves the conversion of (Formula presented.) to (Formula presented.), S0 and (Formula presented.) 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 S0 to (Formula presented.), (Formula presented.) and polythionates in the A. thiooxidans S0 metabolism model. Our combined results shed light onto the important role specifically of TetH in (Formula presented.) metabolism. Also, we show that activity of Hdr proteins rather than Sdo are likely associated with S0 oxidation. Finally, our data suggest that formation of intracellular (Formula presented.) is a critical step in S0 metabolism, and that recycling of internally generated (Formula presented.) occurs, through comproportionating reactions that result in (Formula presented.). Electron microscopy and spectroscopy confirmed intracellular production and storage of S0 during growth on both S0 and (Formula presented.) substrates.