Subsurface processes influence oxidant availability and chemoautotrophic hydrogen metabolism in Yellowstone hot springs

Abstract

The geochemistry of hot springs and the availability of oxidants capable of supporting microbial metabolisms are influenced by subsurface processes including the separation of hydrothermal fluids into vapor and liquid phases. Here, we characterized the influence of geochemical variation and oxidant availability on the abundance, composition, and activity of hydrogen (H )-dependent chemoautotrophs along the outflow channels of two-paired hot springs in Yellowstone National Park. The hydrothermal fluid at Roadside East (RSE; 82.4°C, pH 3.0) is acidic due to vapor-phase input while the fluid at Roadside West (RSW; 68.1°C, pH 7.0) is circumneutral due to liquid-phase input. Most chemotrophic communities exhibited net rates of H oxidation, consistent with H support of primary productivity, with one chemotrophic community exhibiting a net rate of H production. Abundant H -oxidizing chemoautotrophs were supported by reduction in oxygen, elemental sulfur, sulfate, and nitrate in RSW and oxygen and ferric iron in RSE; O utilizing hydrogenotrophs increased in abundance down both outflow channels. Sequencing of 16S rRNA transcripts or genes from native sediments and dilution series incubations, respectively, suggests that members of the archaeal orders Sulfolobales, Desulfurococcales, and Thermoproteales are likely responsible for H oxidation in RSE, whereas members of the bacterial order Thermoflexales and the archaeal order Thermoproteales are likely responsible for H oxidation in RSW. These observations suggest that subsurface processes strongly influence spring chemistry and oxidant availability, which in turn select for unique assemblages of H oxidizing microorganisms. Therefore, these data point to the role of oxidant availability in shaping the ecology and evolution of hydrogenotrophic organisms.

Effects of salinity on microbialite‐associated production in Great Salt Lake, Utah

“…, Lindsay et al. ). DPMs measured in killed controls were subtracted from experimental microcosms, and the average and standard error of the mean of three replicate assays for each microcosm at each salinity are presented (a total of nine assays for each salinity).…”

“…Thirtyfive cycles of PCR were conducted as previously described (Colman et al 2016) at an annealing temperature of 55°C. Quantitative PCR (qPCR) of 16S rRNA genes was performed on DNA extracts using the same primers (515F-806R) and the SsoAdvanced Universal SYBR Green Supermix (Bio-Rad Laboratories, Hercules, California, USA) using previously described methods (Lindsay et al 2018). Plasmid standards for use in relating copy numbers of templates to threshold amplification signals were prepared as described previously (Boyd et al 2011).…”

“…Filters and associated material were placed in scintillation vials and were overlaid with 10 mL of CytoScint ES liquid scintillation fluid. The radioactivity measured in counts per minute (CPM) was measured on a Beckman LS 6500 liquid scintillation counter (Beckman Coulter, Inc., Indianapolis, Indiana, USA) and converted to disintegrations per minute (DPM) and to rates of CO 2 uptake, according to previously published protocols (Urschel et al 2015, Lindsay et al 2018. DPMs measured in killed controls were subtracted from experimental microcosms, and the average and standard error of the mean of three replicate assays for each microcosm at each salinity are presented (a total of nine assays for each salinity).…”

Probing the geological source and biological fate of hydrogen in Yellowstone hot springs

“…Samples for other cations and anions were filtered through a 0.22 μm membrane filter, acidified in Nalgene bottles, and stored at −20°C. Concentrations were determined on a Dionex DX‐600 ion chromatography system according to previously published protocols (Lindsay et al ., ), except that columns were equilibrated for 10 min. prior to each injection.…”

“…Thermodynamic calculations using field geochemical measurements in YNP hot springs indicate H 2 to be a more favourable reductant in springs with acidic pH when compared to those with alkaline pH (Shock et al, 2010). Therefore, it follows that the geological processes that control hot spring geochemical composition, including spring pH and the availability of H 2 and other sources of reductants, likely influence the distribution, abundance and activity of hydrogenotrophic organisms (Lindsay et al, 2018).…”