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 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 - , S ⁰ 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 S ⁰ to SO 3 2 - , S 2 ⁢ O 3 2 - and polythionates in the A. thiooxidans S ⁰ 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 S ⁰ oxidation. Finally, our data suggest that formation of intracellular S 2 ⁢ O 3 2 - is a critical step in S ⁰ 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 S ⁰ during growth on both S ⁰ and S 2 ⁢ O 3 2 - substrates.
(Copyright © 2020 Camacho, Frazao, Fouillen, Nanci, Lang, Apte, Baron and Warren.)