Geomicrobial dynamics of Trans-Himalayan sulfur-borax spring system reveals mesophilic bacteria's resilience to high heat
Date
2020Author
Roy, C.
Mondal, N.
Peketi, A.
Fernandes, S.
Mapder, T.
Volvoikar, S.P.
Haldar, P.K.
Nandi, N.
Bhattacharya, T.
Mazumdar, A.
Chakraborty, R.
Ghosh, W.
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Geomicrobiology of sulfur-boron-dominated, neutral-pH hydrothermal systems was revealed in a Trans-Himalayan spring named Lotus Pond, located at 4436 m, in Puga Valley, Ladakh (India), where water boils at 85°C. Water sampled along Lotus Pond's outflow (vent to an adjacent river called Rulang), representing an 85-14°C gradient, had high microbial diversity and boron/chloride/sodium/sulfate/thiosulfate concentration; potassium/silicon/sulfide/sulfite was moderately abundant, whereas cesium/lithium small but definite. Majority of the bacterial genera identified in the 85-72°C samples have no laboratory-growth reported at >45°C, and some of those mesophiles were culturable. Sulfur-species concentration and isotope-ratio along the hydrothermal gradient, together with the distribution of genera having sulfur-oxidizing members, indicated chemolithotrophic activities in the 85-72°C sites. While biodiversity increased in the vent-to-river trajectory all-day, maximum rise was invariably between the vent (85-81°C) and the 78-72°C site; below 72°C, diversity increased gradually. Biodiversity of the vent-water exhibited diurnal fluxes relatable to the sub-surface-processes-driven temporal fluxes in physicochemical properties of the discharge. Snow-melts infiltrating (via tectonic faults) the ~160°C geothermal reservoir located within the breccia, at ~450 m depth, apparently transport mesophilic microbes into the thermal waters. As these micro-organisms emanate with the vent-water, some remain alive, illustrating that natural bacterial populations are more heat-resilient than their laboratory counterparts.
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