Sulfur Oxygenase Reductase (Sor) in the Moderately Thermoacidophilic Leaching Bacteria: Studies in Sulfobacillus thermosulfidooxidans and Acidithiobacillus caldus

Abstract

The sulfur oxygenase reductase (Sor) catalyzes the oxygen dependent disproportionation of elemental sulfur, producing sulfite, thiosulfate and sulfide. Being considered an “archaeal like” enzyme, it is also encoded in the genomes of some acidophilic leaching bacteria such as Acidithiobacillus caldus, Acidithiobacillus thiooxidans, Acidithiobacillus ferrivorans and Sulfobacillus thermosulfidooxidans, among others. We measured Sor activity in crude extracts from Sb. thermosulfidooxidans DSM 9293T. The optimum temperature for its oxygenase activity was achieved at 75 °C, confirming the “thermophilic” nature of this enzyme. Additionally, a search for genes probably involved in sulfur metabolism in the genome sequence of Sb. thermosulfidooxidans DSM 9293T was done. Interestingly, no sox genes were found. Two sor genes, a complete heterodisulfidereductase (hdr) gene cluster, three tetrathionate hydrolase (tth) genes, three sulfide quinonereductase (sqr), as well as the doxD component of a thiosulfate quinonereductase (tqo) were found. Seven At. caldus strains were tested for Sor activity, which was not detected in any of them. We provide evidence that an earlier reported Sor activity from At. caldus S1 and S2 strains most likely was due to the presence of a Sulfobacillus contaminant.

Microbial Functional Diversity in Vineyard Soils: Sulfur Metabolism and Links With Grapevine Plants and Wine Quality

“…P. denitrificans and T. denitrificans were more abundant in BRO11, where nir genes (niR, nirA, nirB, nirK, and nirS) were significantly enriched, confirming a greater denitrification process compared to BRO12. On the other hand, A. ferrooxidans resulted more enriched in BRO12, thus promoting the oxidation of sulfur to thiosulfate and, ultimately, to sulfate (Guo et al, 2014;Janosch et al, 2015). This result is consistent with the overexpression of sqr and fccAB genes detected in BRO12, which are involved in the sulfur and sulfide oxidation pathways, thus indicating an enhancement of oxidative reactions in S cycling of BRO12 soils.…”

“…The higher presence of Acidithiobacillus ferrooxidans in BRO12 is likely related to its ability to oxidize iron and various reduced inorganic sulfur compounds as energy sources, thus promoting the bioleaching and the extraction of such metals from soil. More specifically, despite its ability to use sulfur as substrate to form thiosulfate S 2 O 2− 3 thus promoting sulfur oxidation, the Sox multienzyme-complex is absent in A. ferrooxidans (Janosch et al, 2015). It worth mentioning the enrichment in Sulfobacillus thermosulfidooxidans sp.…”

Biogeochemical Cycling by a Low-Diversity Microbial Community in Deep Groundwater

“…The proteomes of the Deltaproteobacterial MAGs Desulfomicrobium , Desulfarculus and Pseudodesulfovibrio also harboured a subunit of the protein thiosulphate reductase (PhsA), which catalyses the initial step in the disproportionation of thiosulphate and is relatively common among sulphate-reducing Deltaproteobacteria ( Thorup et al, 2017 ). The Desulfomicrobium MAG additionally harbours a sulphur oxygenase reductase ( sor ) which typically encodes a protein that catalyses the oxygen-dependent disproportionation of elemental sulphur ( Janosch et al, 2015 ). The sor gene has also been reported in the sulphate- and sulphur-reducing Desulfomicrobium baculatum , but the physiological role of this enzyme in strictly anaerobic bacteria is unclear ( Veith et al, 2012 ).…”

Persulfide Dioxygenase From Acidithiobacillus caldus: Variable Roles of Cysteine Residues and Hydrogen Bond Networks of the Active Site

“…The SDO2 protein is 99% identical to the PDO described here. The deletion or overexpression of both sdo genes did not affect the growth properties of MTH-04 on elemental sulfur significantly ( Wu et al, 2017 ) suggesting that other sulfur-oxidizing enzymes like the sulfur oxygenase reductase ( Janosch et al, 2009 , 2015 ) might be more important. A deletion of the sdo1 gene, however, resulted in a complete inability of MTH-04 to grow on tetrathionate ( Wu et al, 2017 ).…”