Metagenomic analyses of a microbial assemblage in a subglacial lake beneath the Vatnajökull ice cap, Iceland

Pauline Vannier; Gregory K Farrant; Alexandra Klonowski; Eric Gaidos; Thorsteinn Thorsteinsson; Viggó Þór Marteinsson

doi:10.3389/fmicb.2023.1122184

Metagenomic analyses of a microbial assemblage in a subglacial lake beneath the Vatnajökull ice cap, Iceland

Front Microbiol. 2023 Mar 30:14:1122184. doi: 10.3389/fmicb.2023.1122184. eCollection 2023.

Authors

Pauline Vannier¹, Gregory K Farrant¹, Alexandra Klonowski¹, Eric Gaidos², Thorsteinn Thorsteinsson³, Viggó Þór Marteinsson^{1

4}

Affiliations

¹ MATIS, Department of Research and Innovation, Reykjavík, Iceland.
² Department of Earth Sciences, University of Hawai'i at Mānoa, Honolulu, HI, United States.
³ Icelandic Meteorological Office, Reykjavík, Iceland.
⁴ Faculty of Food Science and Nutrition, University of Iceland, Reykjavík, Iceland.

Abstract

Skaftárkatlar are two subglacial lakes located beneath the Vatnajökull ice cap in Iceland associated with geothermal and volcanic activity. Previous studies of these lakes with ribosomal gene (16S rDNA) tag sequencing revealed a limited diversity of bacteria adapted to cold, dark, and nutrient-poor waters. In this study, we present analyses of metagenomes from the lake which give new insights into its microbial ecology. Analyses of the 16S rDNA genes in the metagenomes confirmed the existence of a low-diversity core microbial assemblage in the lake and insights into the potential metabolisms of the dominant members. Seven taxonomic genera, Sulfuricurvum, Sulfurospirillum, Acetobacterium, Pelobacter/Geobacter, Saccharibacteria, Caldisericum, and an unclassified member of Prolixibacteraceae, comprised more than 98% of the rDNA reads in the library. Functional characterisation of the lake metagenomes revealed complete metabolic pathways for sulphur cycling, nitrogen metabolism, carbon fixation via the reverse Krebs cycle, and acetogenesis. These results show that chemolithoautotrophy constitutes the main metabolism in this subglacial ecosystem. This assemblage and its metabolisms are not reflected in enrichment cultures, demonstrating the importance of in situ investigations of this environment.

Keywords: Iceland; metabolism; metagenome; microbial assemblage; subglacial lakes.

Grants and funding

This project had received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie actions grant agreement no. 704956. Sampling expeditions and sample analysis were provided by the Icelandic Centre for Research (Contract No. 080222023). Partial support for fieldwork was provided by the National Aeronautics and Space Administration through the NASA Astrobiology Institute under Cooperative Agreement No. NNA04CC08A issued through the Office of Space Science.