Rare Taxa and Microbial Metabolisms in Subglacial Lakes Revealed through Targeted Enrichment
Abstract
Subglacial lakes are difficult to access and the resident microbes are rarely sequenced, grown, or described. Understanding how life persists in these systems may facilitate studies of similar environments on the early Earth, Mars, Europa, and other icy worlds. In this study, samples were obtained from the Skaftarkatlar subglacial lakes of Iceland, which are formed by volcanic heating and melting of the overlying Vatnajokull Ice Cap. Metabolically significant microbial populations and rare members of the microbial community were targeted with a series of enrichments from two Icelandic lakes at multiple depths, and the 16S rRNA gene and the total DNA of the enriched communities were sequenced and analyzed. The enriched microbial communities contain a variety of known psychrophiles, including Brevundimonas, Janthinobacterium, Polaromonas, and Sulfuricurvum. Enrichment experiments that targeted sulfur oxidation, hydrogen oxidation, acetogenesis, and sulfate reduction were successful in selecting for the corresponding metabolisms. Some of the enriched and isolated genera represent relatively rare taxa previously identified in investigations of the lake 16S rRNA gene content. Metagenome Assembled Genomes from the sulfur oxidizing, hydrogen oxidizing, and sulfate reducing enrichments reveal the presence of many different metabolic energy pathways and potentially novel taxa. When compared to the concentrations of sulfate, sulfide, nitrate, acetate, and phosphate from the lakes, the differences in the enriched microbial communities correspond more closely to lake depth and chemical concentration than to the individual lake of origin. Isolates from the sulfur oxidation medium use both sulfide and thiosulfate as electron donors. These results strongly suggest that the Skaftarkatlar microbial populations are influenced by volcanic inputs. Additionally, numerous previously overlooked microbial taxa were enriched and isolated, organisms that may play a significant role in the biogeochemical cycling of sulfur.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B23E2551F
- Keywords:
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- 0444 Evolutionary geobiology;
- BIOGEOSCIENCESDE: 0495 Water/energy interactions;
- BIOGEOSCIENCESDE: 4805 Biogeochemical cycles;
- processes;
- and modeling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICALDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS