New Insights Into Acidithiobacillus thiooxidans Sulfur Metabolism Through Coupled Gene Expression, Solution Chemistry, Microscopy, and Spectroscopy Analyses
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Here, we experimentally expand understanding of the reactions and enzymes involved in Acidithiobacillus thiooxidans ATCC 19377 S0 and S 2 O 3 2 - metabolism by developing models that integrate gene expression analyzed by RNA-Seq, solution sulfur speciation, electron microscopy and spectroscopy. The A. thiooxidans S 2 O 3 2 - metabolism model involves the conversion of S 2 O 3 2 - to SO 4 2 - , S0 and S 4 O 6 2 - , 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 SO 3 2 - , S 2 O 3 2 - and polythionates in the A. thiooxidans S0 metabolism model. Our combined results shed light onto the important role specifically of TetH in S 2 O 3 2 - 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 S 2 O 3 2 - is a critical step in S0 metabolism, and that recycling of internally generated SO 3 2 - occurs, through comproportionating reactions that result in S 2 O 3 2 - . Electron microscopy and spectroscopy confirmed intracellular production and storage of S0 during growth on both S0 and S 2 O 3 2 - substrates.
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