Abstract
Thioarsenates are common arsenic species in sulfidic geothermal waters, yet little is known about their biogeochemical traits. In the present study, a novel sulfate-reducing bacterial strain Desulfotomaculum TC-1 was isolated from a sulfidic hot spring in Tengchong geothermal area, Yunnan Province, China. The arxA gene, encoding anaerobic arsenite oxidase, was successfully amplified from the genome of strain TC-1, indicating it has a potential ability to oxidize arsenite under anaerobic condition. In anaerobic arsenite oxidation experiments inoculated with strain TC-1, a small amount of arsenate was detected in the beginning but became undetectable over longer time. Thioarsenates (AsO4-xSx2- with x = 1–4) formed with mono-, di- and tri-thioarsenates being dominant forms. Tetrathioarsenate was only detectable at the end of the experiment. These results suggest that thermophilic microbes might be involved in the formation of thioarsenates and provide a possible explanation for the widespread distribution of thioarsenates in terrestrial geothermal environments.
Highlights
High concentrations of arsenic have been reported in global terrestrial hot springs (McKenzie et al, 2001; Cleverley et al, 2003; Aiuppa et al, 2006; Pascua et al, 2007; Landrum et al, 2009; McCleskey et al, 2010)
One geochemical study on arsenic speciation in the Tengchong geothermal zone (TGZ) of Yunnan Province, China reported that thioarsenates are widely distributed in the high-sulfidic Tengchong hot springs (Guo et al, 2017)
We provided biological evidence on the potential involvement of a novel sulfate-reducing bacterium isolated from a TGZ hot spring, designated as Desulfotomaculum sp
Summary
High concentrations of arsenic have been reported in global terrestrial hot springs (McKenzie et al, 2001; Cleverley et al, 2003; Aiuppa et al, 2006; Pascua et al, 2007; Landrum et al, 2009; McCleskey et al, 2010). The aioA and arxA genes have become molecular biomarkers to study the distribution and activity of arsenite-oxidizing bacteria in natural environments (Hamamura et al, 2009, 2010, 2014; Zargar et al, 2012; Engel et al, 2013; Jiang et al, 2014; Wu et al, 2015; Hernandez-Maldonado et al, 2016). One geochemical study on arsenic speciation in the Tengchong geothermal zone (TGZ) of Yunnan Province, China reported that thioarsenates are widely distributed in the high-sulfidic Tengchong hot springs (Guo et al, 2017). The results in this study suggested that microbial activities may be involved in the formation of thioarsenates in geothermal features and could explain the reported distribution of thioarsenates in sulfidic hot springs
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