Defining the Functional Potential and Active Community Members of a Sediment Microbial Community in a High-Arctic Hypersaline Subzero Spring

Abstract

bThe Lost Hammer (LH) Spring is the coldest and saltiest terrestrial spring discovered to date and is characterized by perennial discharges at subzero temperatures (؊5°C), hypersalinity (salinity, 24%), and reducing (Ϸ؊165 mV), microoxic, and oligotrophic conditions. It is rich in sulfates (10.0%, wt/wt), dissolved H 2 S/sulfides (up to 25 ppm), ammonia (Ϸ381 M), and methane (11.1 g day ؊1 ). To determine its total functional and genetic potential and to identify its active microbial components, we performed metagenomic analyses of the LH Spring outlet microbial community and pyrosequencing analyses of the cDNA of its 16S rRNA genes. Reads related to Cyanobacteria (19.7%), Bacteroidetes (13.3%), and Proteobacteria (6.6%) represented the dominant phyla identified among the classified sequences. Reconstruction of the enzyme pathways responsible for bacterial nitrification/denitrification/ammonification and sulfate reduction appeared nearly complete in the metagenomic data set. In the cDNA profile of the LH Spring active community, ammonia oxidizers (Thaumarchaeota), denitrifiers (Pseudomonas spp.), sulfate reducers (Desulfobulbus spp.), and other sulfur oxidizers (Thermoprotei) were present, highlighting their involvement in nitrogen and sulfur cycling. Stress response genes for adapting to cold, osmotic stress, and oxidative stress were also abundant in the metagenome. Comparison of the composition of the functional community of the LH Spring to metagenomes from other saline/ subzero environments revealed a close association between the LH Spring and another Canadian high-Arctic permafrost environment, particularly in genes related to sulfur metabolism and dormancy. Overall, this study provides insights into the metabolic potential and the active microbial populations that exist in this hypersaline cryoenvironment and contributes to our understanding of microbial ecology in extreme environments. Cryoenvironments are defined as permanently subzero or frozen environments, such as permafrost, glaciers, ice sheets, multiyear sea ice, high-elevation Antarctic dry valleys, and some cold saline springs (1-6). Microorganisms inhabiting cryoenvironments must face the challenges of subzero temperatures, low water activity, and, often, high solute concentrations to sustain their viability. The cold saline springs on Axel Heiberg Island (AHI) in the Canadian high Arctic discharge through 500 to 600 m of thick permafrost, maintain a liquid state at subzero temperatures, and offer a unique opportunity to assess microbial adaptations to extremes of both high salinity and subzero temperatures (3, 4, 7-9). These springs occur in an area with an average annual air temperature of Ϫ15°C, reaching below Ϫ40°C during the winter months, and probably originate from subpermafrost groundwater flow through carboniferous evaporites in areas of diapiric uplift on AHI (10, 11). Other Arctic cold springs, on Ellesmere Island in the Canadian high Arctic and on the Norwegian highArctic Svalbard archipelago, have been reported (12-14), although t...

Natural Analogue Constraints on Europa's Non‐ice Surface Material

“…Brine compositions and salt mineralogy at the springs are consistent with published data (Battler et al, ; Lay et al, ; Omelon et al, ; Ward & Pollard, ). Across all springs, fluids are dominated by sodium and chloride and contain significant concentrations of sulfate (Figure a and Table S1).…”

Viral Induced Microbial Mortality in Arctic Hypersaline Spring Sediments

“…The abundant ions of LH are the same as GH4, in similar ratios but greater concentrations (Niederberger et al, 2010). Microbial and molecular characterization from both the spring outlet and channel indicate a low diversity community and the presence of anaerobic methanotrophs, methanogens, sulfur oxidizing bacteria and ammonia oxidizers (Niederberger et al, 2010; Lay et al, 2012, 2013; Lamarche-Gagnon et al, 2015). The biomass of both springs are very low, with the channel sediments of each inhabited by an order of magnitude more microbes than the outlet of the same spring (Colangelo-Lillis et al, 2016b).…”

“…Four of these vials were amended with lactate and another four with acetate (60 μL of 1 M carbon source, final concentration 10 mM). Per spring site, EdU ± carbon treated vials were formaldehyde fixed at time points: 0, 8, 24, and 96 h. Lactate was chosen because it can be utilized by many sulfate-reducers, known to be present and active in these sediments (Perreault et al, 2007; Lay et al, 2013). Acetate was chosen as it is among the most simple and ubiquitously utilized carbon sources, and has been employed in culturing isolates from LH (Niederberger et al, 2010).…”

“…Methods employed here did not distinguish between Bacteria, Archaea, and small single-celled Eukaryota. Members of each domain have been reported in both springs (Perreault et al, 2007, 2008; Niederberger et al, 2010; Lay et al, 2012, 2013) and are herein collectively referred to as microbes.…”

Microbial dynamics in a thawing world: Microbial ecology of a permafrost active layer

“…However, E. sibiricu lost flagella at -2.5 °C, in contrast to P. halocryophilus which becomes motile at -15 °C. Metagenomic analysis of low temperature microbial communities in a high-arctic subzero hypersaline spring also revealed high abundance of genes associated with unsaturated fatty acid metabolism, suggestive of cell wall remodeling, along with periplasmic glucan, and cytosolic betaine synthesis genes associated with osmotolerance (betaine balances high osmotic pressure in high saline environments) (Lay et al, 2013). Oxidative stress genes were also highly abundant which has been attributed to a requirement to detoxify reactive radicals resulting from accumulation of electrons in the respiratory chain at very low metabolic rates (Lay et al, 2013).…”