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

David Camacho,Rodolfo Frazao,Antonio Nanci,Christian Baron,B Franz Lang,Simon C Apte,Lesley A Warren,Aurélien Fouillen

doi:10.3389/fmicb.2020.00411

Abstract

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

Highlights

The stepwise oxidation of reduced sulfur species from sulfide to sulfate can occur via several pathways involving a variety of sulfur oxidation intermediate (SOI) compounds that are dynamically influenced by environmental and geochemical characteristics as well as the microbes involved (Schippers et al, 1996; Schippers and Sand, 1999; Nordstrom, 2015)
The plasmids apparently do not code for genes that are of interest in this context, with the potential exception of a gene for a “divalent metal cation transporter” (MntH), which may have been recruited via a plasmid to manage the high metal ion concentrations in its natural environment
Models of A. thiooxidans S0 and S2O23− Metabolism By combining the analysis of gene expression, solution sulfur speciation and electron microscopy, our results provide new insights into A. thiooxidans sulfur metabolism revealing the importance of intracellular pathways

Summary

Introduction

The stepwise oxidation of reduced sulfur species from sulfide to sulfate can occur via several pathways involving a variety of sulfur oxidation intermediate (SOI) compounds that are dynamically influenced by environmental and geochemical characteristics as well as the microbes involved (Schippers et al, 1996; Schippers and Sand, 1999; Nordstrom, 2015) This range of Acidithiobacillus thiooxidans Sulfur Metabolism sulfur oxidation states contributes to a complex, and only partially constrained biogeochemical cycle in which sulfur compounds can be variably reduced, oxidized and disproportionated via abiotic and/or biotic processes depending on environmental conditions (Johnston and McAmish, 1973; Kelly and Baker, 1990; Pronk et al, 1990; Druschel, 2002; Zopfi et al, 2004; Bernier and Warren, 2007; Boyd and Druschel, 2013). Sulfur mass balance is rarely employed in studies of sulfur cycling

Methods

Results

Discussion

Conclusion