Abstract
Antarctic cryptoendolithic communities are self-supporting borderline ecosystems spreading across the extreme conditions of the Antarctic desert and represent the predominant life-form in the ice-free areas of McMurdo Dry Valleys, accounted as the closest terrestrial Martian analogue. Components of these communities are highly adapted extremophiles and extreme-tolerant microorganisms, among the most resistant known to date. Recently, studies investigated biodiversity and community composition in these ecosystems but the metabolic activity of the metacommunity has never been investigated. Using an untargeted metabolomics, we explored stress-response of communities spreading in two sites of the same location, subjected to increasing environmental pressure due to opposite sun exposure, accounted as main factor influencing the diversity and composition of these ecosystems. Overall, 331 altered metabolites (206 and 125 unique for north and south, respectively), distinguished the two differently exposed communities. We also selected 10 metabolites and performed two-stage Receiver Operating Characteristic (ROC) analysis to test them as potential biomarkers. We further focused on melanin and allantoin as protective substances; their concentration was highly different in the community in the shadow or in the sun. These results clearly indicate that opposite insolation selected organisms in the communities with different adaptation strategies in terms of key metabolites produced.
Highlights
The Antarctic cryptoendolithic communities are microbial ecosystems that dominate the biology of most ice-free areas in Continental Antarctica
An untargeted metabolomics analysis was performed on six differently exposed rocks and more than 10,000 peaks per sample were referred to the KEGG database; among them, 2,807 metabolites were analysed more precisely and identified
The significant discriminating metabolites were identified using the Volcano plot analysis (Fig 2); the univariate analysis identified significant accumulation of specific metabolites; most of them were expressed in rocks collected in south exposure, while few others were overexpressed in north exposed rocks
Summary
The Antarctic cryptoendolithic communities are microbial ecosystems that dominate the biology of most ice-free areas in Continental Antarctica. They were described for the first time in the McMurdo Dry Valleys, Southern Victoria Land [1], the largest ice-free area of the continent. Analysed, stored in the Culture Collection of Fungi from Extreme Environments (CCFEE), University of Tuscia, Italy. The authors wish to thank Italian Space Agency The authors wish to thank Italian Space Agency (ASI n. 2018-6-U0) for co-funding the BIOSIGNMicrofossils project
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