AUTHOR=Camacho David , Frazao Rodolfo , Fouillen Aurélien , Nanci Antonio , Lang B. Franz , Apte Simon C. , Baron Christian , Warren Lesley A. TITLE=New Insights Into Acidithiobacillus thiooxidans Sulfur Metabolism Through Coupled Gene Expression, Solution Chemistry, Microscopy, and Spectroscopy Analyses JOURNAL=Frontiers in Microbiology VOLUME=11 YEAR=2020 URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00411 DOI=10.3389/fmicb.2020.00411 ISSN=1664-302X ABSTRACT=

Here, we experimentally expand understanding of the reactions and enzymes involved in Acidithiobacillus thiooxidans ATCC 19377 S⁰ and S2⁢O32- metabolism by developing models that integrate gene expression analyzed by RNA-Seq, solution sulfur speciation, electron microscopy and spectroscopy. The A. thiooxidansS2⁢O32- metabolism model involves the conversion of S2⁢O32- to SO42-, S⁰ and S4⁢O62-, 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 SO32-, S2⁢O32- and polythionates in the A. thiooxidans S⁰ metabolism model. Our combined results shed light onto the important role specifically of TetH in S2⁢O32- 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 S2⁢O32- is a critical step in S⁰ metabolism, and that recycling of internally generated SO32- occurs, through comproportionating reactions that result in S2⁢O32-. Electron microscopy and spectroscopy confirmed intracellular production and storage of S⁰ during growth on both S⁰ and S2⁢O32- substrates.