Metagenomic Insights into Microbial Metabolisms of a Sulfur-Influenced Glacial Ecosystem

Abstract

25Biological sulfur cycling in polar, low-temperature ecosystems is an understudied 26 phenomenon in part due to difficulty of access and the ephemeral nature of such environments. 27 One such environment where sulfur cycling plays an important role in microbial metabolisms is 28 located at Borup Fiord Pass (BFP) in the Canadian High Arctic. Here, transient springs emerge 29 from the toe of a glacier creating a large proglacial aufeis (spring-derived ices) that are often 30 covered in bright yellow/white sulfur, sulfate, and carbonate mineral precipitates that are 31 accompanied by a strong odor of hydrogen sulfide. Metagenomic sequencing from multiple 32 sample types at sites across the BFP glacial system produced 31 highly complete metagenome 33 assembled genomes (MAGs) that were queried for sulfur-, nitrogen-and carbon-34 cycling/metabolism genes. Sulfur cycling, especially within the Sox complex of enzymes, was 35 widespread across the isolated MAGs and taxonomically associated with the bacterial classes 36 Alpha-, Beta-, Gamma-, and Epsilon-Proteobacteria. While this does agree with previous 37 research from BFP implicating organisms within the Gamma-and Epsilon-Proteobacteria as the 38 primary classes responsible for sulfur oxidation, our new data suggests putative sulfur oxidation 39 by organisms within Alpha-and Beta-Proteobacterial classes which was not predicted. These 40 findings indicate that in a low-temperature, ephemeral sulfur-based environment such as this, 41functional redundancy may be a key mechanism that microorganisms use to co-exist whenever 42 energy is limited and/or focused by redox chemistry. 43 44 Importance 45 Borup Fiord Pass is a unique environment characterized by a sulfur-enriched glacial 46 ecosystem, in the low-temperature environment of the Canadian High Arctic. This unique 47 3combination makes BFP one of the best analog sites for studying icy, sulfur-rich worlds outside 48 of our own, such as Europa and Mars. The site also allows investigation of sulfur-based 49 microbial metabolisms in cold environments here on Earth. Herein, we report whole genome 50 sequencing data that suggests sulfur cycling metabolisms at BFP are more widely used across 51 bacterial taxa than predicted. From our data, the metabolic capability of sulfur oxidation among 52 multiple community members appears likely due to functional redundancy within their genomes. 53Functional redundancy, with respect to sulfur-oxidation at BFP, may indicate that this dynamic 54 ecosystem hosts microorganisms that are able to use multiple sulfur electron donors alongside 55 other important metabolic pathways, including those for carbon and nitrogen. 56 57

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

“…Full-length sequences permitted a more precise taxonomic assignment of the most abundant community members as well as 14 minor taxa with relative abundance ranging from 0.05 to 1%. Many of these taxa are closely related to psychrotolerant strains, including a member of Brevundimonas, a taxon detected in the Arctic (Trivedi et al, 2018) and Antarctic (González-Toril et al, 2009) and which is known to be resistant to cold temperatures (Dartnell et al, 2010) and the genus Pedobacter, also found in Arctic environments (Zhou et al, 2012;Peter and Sommaruga, 2016;Trivedi et al, 2018).…”