Role of extracellular reactive sulfur metabolites on microbial Se(0) dissolution

Abstract

The dissolution of elemental selenium [Se(0)] during chemical weathering is an important step in the global selenium cycle. While microorganisms have been shown to play a key role in selenium dissolution in soils, the mechanisms of microbial selenium solubilization are poorly understood. In this study, we isolated a Bacillus species, designated as strain JG17, that exhibited the ability to dissolve Se(0) under oxic conditions and neutral pH. Growth of JG17 in a defined medium resulted in the production and accumulation of extracellular compounds that mediated Se(0) dissolution. Analysis of the spent medium revealed the presence of extracellular sulfite, sulfide, and thiosulfate. Abiotic Se(0) dissolution experiments with concentrations of sulfite, sulfide, and thiosulfate relevant to our system showed similar extents of selenium solubilization as the spent medium. Together, these results indicate that the solubilization of Se(0) by JG17 occurs via the release of extracellular inorganic sulfur compounds followed by chemical dissolution of Se(0) by the reactive sulfur metabolites. Our findings suggest that the production of reactive sulfur metabolites by soil microorganisms and the formation of soluble selenosulfur complexes can promote selenium mobilization during chemical weathering.

Selenite Stable Isotope Fractionation during Abiotic Reduction by Sodium Sulfide

“…Combined, these two S species account for <3% of the mass of S added. The presence of oxidized S species can result in the oxidation of Se(0) at pH > 7 . The pH was not measured during sample collection.…”

“…The presence of oxidized S species can result in the oxidation of Se(0) at pH > 7. 49 The pH was not measured during sample collection. If the pH increased after the precipitation reaction, it is possible that oxidized S species could oxidize Se(0), if left in contact for over 2 days.…”

Extracellular sulfite is protective against reactive oxygen species and antibiotic stress in Shewanella oneidensis MR‐1

“…The production and release of significant quantities of sulfite from the assimilatory sulfate reduction pathway is a well‐documented process in eukaryotic yeasts (Dott and Trüper, 1976). A similar process for extracellular sulfite production in a Bacillus strain was also recently suggested (Goff et al ., 2019). Shewanella oneidensis MR‐1 has homologues to the entire sulfate assimilation pathway that is well characterized in E. coli .…”

Selenium species transforming along soil–plant continuum and their beneficial roles for horticultural crops

“…1 ). Several studies have considered the crucial roles of microorganisms in influencing the biogeochemical cycle of Se (reduction, methylation, or oxidation), which alter Se speciation and contents [ 9 – 11 ]. However, the results of most studies have utilized culture-based approaches, and individual microorganisms involved in Se species transformation in Se cycling processes have been identified.…”