Cryptic roles of tetrathionate in the sulfur cycle of marine sediments: microbial drivers and indicators
<p>To explore the potential role of tetrathionate in the sedimentary sulfur cycle, population ecology of microorganisms capable of metabolizing this polythionate was revealed at 15–30 cm resolution along two, <span class="inline-formula">∼3</span> m...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-09-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/17/4611/2020/bg-17-4611-2020.pdf |
| Summary: | <p>To explore the potential role of tetrathionate in the sedimentary sulfur
cycle, population ecology of microorganisms capable of metabolizing this
polythionate was revealed at 15–30 cm resolution along two, <span class="inline-formula">∼3</span> m long, cores collected from 530 and 580 m below the sea level, off
India's west coast, within the oxygen minimum zone (OMZ) of the Arabian Sea.
Metagenome analysis along the cores revealed widespread occurrence of genes
involved in the formation, oxidation, and reduction of tetrathionate; high
diversity and relative abundance were also detected for bacteria that are
known to render these metabolisms in vitro. Results of slurry culture of the
sediment samples in thiosulfate- or tetrathionate-containing microbial
growth media, data obtained via pure-culture isolation, and finally
metatranscriptome analyses corroborated the in situ functionality of the
tetrathionate-forming, tetrathionate-oxidizing, and tetrathionate-reducing microorganisms. Ion
chromatography of pore waters revealed the presence of up to 11.1 <span class="inline-formula">µ</span>M
thiosulfate in the two cores, whereas tetrathionate remained undetected in
spectroscopic assay based on its reaction with cyanide. While thiosulfate
oxidation by chemolithotrophic bacteria prevalent in situ is the apparent source of
tetrathionate in this ecosystem, high biochemical and geochemical reactivity
of this polythionate could be instrumental in its cryptic status in the
sulfur cycle. Potential abiotic origin of tetrathionate in the
sediment horizon explored could neither be ruled out nor confirmed from the
geochemical information available. On the other hand, tetrathionate
potentially present in the system can be either oxidized to sulfate or
reduced back to thiosulfate/sulfide via chemolithotrophic oxidation and
respiration by native bacterial populations, respectively. Up to 2.01 mM
sulfide present in the sediment cores may also reduce tetrathionate
abiotically to thiosulfate and elemental sulfur. However, in the absence of
measured data for <span class="inline-formula">O<sub>2</sub></span> or other oxyanions having possibilities of serving
as electron acceptors, the biogeochemical modalities of the oxidative half
of the tetrathionate cycle remained unresolved.</p> |
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| ISSN: | 1726-4170 1726-4189 |