Dynamics of microbial stress responses driven by abiotic changes along a temporal gradient in Deception Island, Maritime Antarctica.

Whalers Bay (WB), Deception Island, is an environment that can drastically change its temperature within a few meters. The main forms of life inhabiting this environment are microorganisms, which, due to the high diversity and their adaptive potential, can survive and thrive under harsh stress conditions. However, the genetic potential and mechanisms to cope with fluctuating adverse conditions as well as what extent environmental variations shape the microbial community over the years it is still unknown in Antarctic environments. In this work, sediments collected in a transect in Whalers Bay, Deception Island, during the Austral Summers of 2014, 2015 and 2017 were analyzed using shotgun metagenomics. Sequence data were further processed with the SqueezeMeta tool for assembly, gene prediction, mapping, taxonomic and functional annotations. Results showed that stress-related functions had the influence of temperatures and solar radiation observed in the years of 2015 and 2017. The most differentiated functions were the ones related to oxidative stress, comparing 2014 vs 2015 and 2014 vs 2017. The genes coding for HSP20 and oxidoreductases (nrdH, grxA, korC and korD), as well as the genes clpE, cspL, and operons mtrAB and vicKR, were differentially enriched between the years, most of them found in gram-positive bacteria. The selective pressures of temperature and radiation may have favored the growth of gram-positive bacteria in 2017, with emphasis on Arthrobacter genus. Data gathered in this work showed that temperature and solar radiation could potentially be the primary driving forces shaping the repertoire of stress-response genes for the maintenance of microbial diversity in WB Antarctic sediments.

Unveiling resistome profiles in the sediments of an Antarctic volcanic island.

The Deception Island, located in Maritime Antarctica, is a volcanic island with geothermal activity and one of the most visited by tourists. However, the extent of the anthropogenic impact remains largely unknown and the factors shaping the resistance/tolerance mechanisms in the microbiomes from Whalers Bay ecosystems have never been investigated. In this context, this study aimed to reveal the resistome profiles of Whalers Bay sediments and correlate them with environmental factors. Samples were collected at four sites during the summer 2014/2015 along a transect of 27.5 m in the Whalers Bay sediments. DNA isolated from sediment samples was sequenced using the Illumina HiSeq platform. Bioinformatic analyses allowed the assembly of contigs and scaffolds, prediction of ORFs, and taxonomic and functional annotation using NCBI RefSeq database and KEGG orthology, respectively. Microorganisms belonging to the genera Psychrobacter, Flavobacterium and Polaromonas were shown to dominate all sites, representing 60% of taxonomic annotation. Arsenic (As), copper (Cu) and iron (Fe) were the most abundant metal resistance/tolerance types found in the microbiomes. Beta-lactam was the most common class related to antibiotics resistance/tolerance, corroborating with previous environmental resistome studies. The acridine class was the most abundant amongst the biocide resistance/tolerances, related to antiseptic compounds. Results gathered in this study reveal a repertoire of resistance/tolerance classes to antibiotics and biocides unusually found in Antarctica. However, given the volcanic nature (heavy metals-rich region) of Deception Island soils, this putative impact must be viewed with caution.

Taxonomic assessment and enzymes production by yeasts isolated from marine and terrestrial Antarctic samples.

The aim of the present study was to investigate the taxonomic identity of yeasts isolated from the Antarctic continent and to evaluate their ability to produce enzymes (lipase, protease and xylanase) at low and moderate temperatures. A total of 97 yeast strains were recovered from marine and terrestrial samples collected in the Antarctica. The highest amount of yeast strains was obtained from marine sediments, followed by lichens, ornithogenic soils, sea stars, Salpa sp., algae, sea urchin, sea squirt, stone with lichens, Nacella concinna, sea sponge, sea isopod and sea snail. Data from polyphasic taxonomy revealed the presence of 21 yeast species, distributed in the phylum Ascomycota (n = 8) and Basidiomycota (n = 13). Representatives of encapsulated yeasts, belonging to genera Rhodotorula and Cryptococcus were recovered from 7 different Antarctic samples. Moreover, Candida glaebosa, Cryptococcus victoriae, Meyerozyma (Pichia) guilliermondii, Rhodotorula mucilaginosa and R. laryngis were the most abundant yeast species recovered. This is the first report of the occurrence of some species of yeasts recovered from Antarctic marine invertebrates. Additionally, results from enzymes production at low/moderate temperatures revealed that the Antarctic environment contains metabolically diverse cultivable yeasts, which could be considered as a target for biotechnological applications. Among the evaluated yeasts in the present study 46.39, 37.11 and 14.43 % were able to produce lipase (at 15 °C), xylanase (at 15 °C) and protease (at 25 °C), respectively. The majority of lipolytic, proteolytic and xylanolytic strains were distributed in the phylum Basidiomycota and were mainly recovered from sea stars, lichens, sea urchin and marine sediments.