Metagenomic Analysis of the Methane-rich Anoxic Basin of the Antarctic Lake Untersee as an Enceladus Analog.

Abstract:

Biological methane production may be possible on Enceladus [1] and other ocean worlds [2]. Using an isolated, perennially ice-covered Antarctic lake with near freezing temperatures and almost no light reaching its deeper sections as an analog, we study the chemosynthetic pathways used by life in an extreme environment with relevant similarities to ocean worlds. While the top 50m of Untersee’s anoxic basin are well-mixed [4], there is an oxycline zone from 65-75m, below which there is a uniformly anoxic region. With CH₄ concentrations up to 21.8 mM, these anoxic waters comprise one of the most methane-rich aquatic ecosystems on Earth [3]. In Fall 2018, we collected samples from the water column as well as Untersee’s benthic lake sediments using sterile techniques. Using a concentrator pipette (Innova Prep), DNA was extracted from these samples and sequenced using next-generation sequencing techniques, and multiple bioinformatics pipelines were used for analysis. We found a great abundance of Unclassified organisms recognized as Microbial Dark Matter, which point to an opportunity to broaden our understanding of communities living in extreme Antarctic environments. We are focusing on the metabolic collaboration between the classified and unclassified microbial communities. Additionally, we are studying the metabolic processes focused on methane oxidation and sulfur reduction since these pathways are linked in anaerobic environments. These results will give us the opportunity to learn more about the habitability of Enceladus, and warrant additional study of sources of energy as well as metabolic processes occurring in the water column and benthic sediments.

[1] Taubner, R., Nature Communications, 2018 [2] Seckbach, J., Kluwer Academic Publishers, 2004 [3] Wand, U., Limnology and Oceanography, 2006 [4] Bevington, J., Antarctic Science 2018