04 Jul 2019
04 Jul 2019
Status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Cryptic role of tetrathionate in the sulfur cycle: A study from Arabian Sea oxygen minimum zone sediments

Subhrangshu Mandal1, Sabyasachi Bhattacharya1, Chayan Roy1, Moidu Jameela Rameez1, Jagannath Sarkar1, Svetlana Fernandes2, Tarunendu Mapder3, Aditya Peketi2, Aninda Mazumdar2, and Wriddhiman Ghosh1 Subhrangshu Mandal et al.
  • 1Department of Microbiology, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata 700054, India
  • 2CSIR-National Institute of Oceanography, Dona Paula, Goa 403004, India
  • 3ARC CoE for Mathematical and Statistical Frontiers, School of Mathematical Sciences, Queensland University of Technology, Brisbane, QLD 4000, Australia

Abstract. To explore the potential role of tetrathionate in the sulfur cycle of marine sediments, the population ecology of tetrathionate-forming, oxidizing, and respiring microorganisms was revealed at 15–30 cm resolution along two, ~ 3-m-long, cores collected from 530- and 580-mbsl water-depths of Arabian Sea, off India’s west coast, within the oxygen minimum zone (OMZ). Metagenome analysis along the two sediment-cores revealed widespread occurrence of the structural genes that govern these metabolisms; high diversity and relative-abundance was also detected for the bacteria known to render these processes. Slurry-incubation of the sediment-samples, pure-culture isolation, and metatranscriptome analysis, corroborated the in situ functionality of all the three metabolic-types. Geochemical analyses revealed thiosulfate (0–11.1 µM), pyrite (0.05–1.09 wt %), iron (9232–17234 ppm) and manganese (71–172 ppm) along the two sediment-cores. Pyrites (via abiotic reaction with MnO2) and thiosulfate (via oxidation by chemolithotrophic bacteria prevalent in situ) are apparently the main sources of tetrathionate in this ecosystem. Tetrathionate, in turn, can be either converted to sulfate (via oxidation by the chemolithotrophs present) or reduced back to thiosulfate (via respiration by native bacteria); 0–2.01 mM sulfide present in the sediment-cores may also reduce tetrathionate abiotically to thiosulfate and elemental sulfur. Notably tetrathionate was not detected in situ – high microbiological and geochemical reactivity of this polythionate is apparently instrumental in the cryptic nature of its potential role as a central sulfur cycle intermediate. Biogeochemical roles of this polythionate, albeit revealed here in the context of OMZ sediments, may well extend to the sulfur cycles of other geomicrobiologically-distinct marine sediment horizons.

Subhrangshu Mandal et al.

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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Subhrangshu Mandal et al.

Subhrangshu Mandal et al.


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Short summary
Sulfur cycling is a crucial component of sediment biogeochemistry within the marine realm. Microbial processes of sulfur cycle work in conjunction with the carbon cycle to remineralize organic matters sequestered in the sea-bed, influenceing metal deposition. Whereas thiosulfate has long been appreciated as a key junction in the sulfur cycle of global marine sediment, the present geomicrobial study brings to the fore hitherto-unappreciated roles of tetrathionate.