Abstract
Nunataks are permanent ice-free rocky peaks that project above ice caps in polar regions, thus being exposed to extreme climatic conditions throughout the year. They undergo extremely low temperatures and scarcity of liquid water in winter, while receiving high incident and reflected (albedo) UVA-B radiation in summer. Here, we investigate the geomicrobiology of the permanently exposed lithic substrates of nunataks from Livingston Island (South Shetlands, Antarctic Peninsula), with focus on prokaryotic community structure and their main metabolic traits. Contrarily to first hypothesis, an extensive sampling based on different gradients and multianalytical approaches demonstrated significant differences for most geomicrobiological parameters between the bedrock, soil, and loose rock substrates, which overlapped any other regional variation. Brevibacillus genus dominated on bedrock and soil substrates, while loose rocks contained a diverse microbial community, including Actinobacteria, Alphaproteobacteria and abundant Cyanobacteria inhabiting the milder and diverse microhabitats within. Archaea, a domain never described before in similar Antarctic environments, were also consistently found in the three substrates, but being more abundant and potentially more active in soils. Stable isotopic ratios of total carbon (δ 13C) and nitrogen (δ 15N), soluble anions concentrations, and the detection of proteins involved in key metabolisms via the Life Detector Chip (LDChip), suggest that microbial primary production has a pivotal role in nutrient cycling at these exposed areas with limited deposition of nutrients. Detection of stress-resistance proteins, such as molecular chaperons, suggests microbial molecular adaptation mechanisms to cope with these harsh conditions. Since early Mars may have encompassed analogous environmental conditions as the ones found in these Antarctic nunataks, our study also contributes to the understanding of the metabolic features and biomarker profiles of a potential Martian microbiota, as well as the use of LDChip in future life detection missions.
Highlights
A small area on Antarctica is permanently ice-free, corresponding to approximately 49,500 km2 (0.35–0.40% of total surface (Bockheim et al, 2015; Convey et al, 2018)
Similar environmental parameters are described for the islands within the South Shetlands archipelago, TOC, and TN values found at Hurd Peninsula nunataks are more comparable to those found for Dry Valleys soils – subjected to much more severe conditions, especially in terms of low water content and temperature
The specific combination of extreme physicochemical parameters in these unique nunatak environments suppresses most of microbial groups, while the prevailing taxa show different adaptation strategies to cope with these conditions
Summary
A small area on Antarctica is permanently ice-free, corresponding to approximately 49,500 km (0.35–0.40% of total surface (Bockheim et al, 2015; Convey et al, 2018). Exposed terrains in most of the Antarctic ice-free regions mainly consist of sandy material with very low organic matter and microbial populations (Lambrechts et al, 2019). They can be considered representatives of one of four different orders of soil, i.e. Gelisols, Entisols, Inceptisols and Histosols (Cowan et al, 2014; Bockheim et al, 2015; Garrido-Benavent et al, 2020). Nunataks can be found in continental and peninsular (including archipelagos close to it) regions of Antarctica, they have received little attention from a biological perspective, with only a few studies analysing nunatak microbiology in the last decades [e.g., (Brinkmann et al, 2007; Yergeau et al, 2009), both studying Coal Nunatak in Alexander Island, 72°03' S 68°31' W, and (Almela et al, 2021), not focused but including samples from Clark Nunatak, Byers Peninsula, Livingston Island]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
