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a Map of Antarctica showing the widespread distribution of brine ecosystems; b focus on the exact location of brine ecosystems in MDV. Image credit: Google Earth/PGC/NASA/U.S. (Geological Survey/Landsat/Copernicus)
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One of the main objectives of astrobiological research is the investigation of the habitability of other planetary bodies. Since space exploration missions are expensive and require long-term organization, the preliminary study of terrestrial environments is an essential step to prepare and support exploration missions. The Earth hosts a multitude...
Citations
... Moreover, this microbiota would have developed remarkable adaptations, including salient metabolic features and molecular mechanisms, to resist the harsh environment (Ramasamy et al., 2023). Thus, their study is valuable to expand our knowledge of on-the-edge life on Earth and possibly other planets (Cassaro et al., 2021;Correa and Abreu, 2020;Pacheco et al., 2019). ...
The high-latitude regions of Antarctica remain among the most remote, extreme, and least explored areas on Earth. Despite the highly restrictive conditions, microbial life has been found in these environments, although with limited information on their genetic properties and functional capabilities. Moreover, the accelerated melting of the Antarctic permafrost, the increasing exposure of soils, and the growing human transit pose the question of whether these environments could be a source of microbes or genes that could emerge and cause global health problems. In this line, although a high bacterial diversity and autochthonous multidrug-resistant bacteria have been found in soils of the Antarctic Peninsula, we still lack information regarding the resistome of areas closer to the South Pole. Moreover, no previous studies have evaluated the pathogenic potential of microbes inhabiting Antarctic soils. In this work, we combined metagenomic and culture-dependent approaches to investigate the microbial diversity, resistome, virulome, and mobile genetic elements (MGEs) in soils from Union Glacier, a high-latitude cold desert in West Antarctica. Despite the low organic matter content, diverse bacterial lineages were found, predominating Actinomycetota and Pseudomonadota, with limited archaeal and fungal taxa. We recovered more than 80 species-level representative genomes (SRGs) of predominant bacterial taxa and the archaeon Nitrosocosmicus sp. Diverse putative resistance and virulence genes were predicted among the SRGs, metagenomic reads, and contigs. Furthermore, we characterized bacterial isolates resistant to up to 24 clinical antibiotics, mainly Pseudomonas , Arthrobacter , Plantibacter, and Flavobacterium . Moreover, some isolates produced putative virulence factors, including siderophores, pyocyanins, and exoenzymes with hemolytic, lecithinase, protease, and DNAse activity. This evidence uncovers a largely unexplored resistome and virulome hosted by deep Antarctica’s soil microbial communities and the presence of bacteria with pathogenic potential, highlighting the relevance of One Health approaches for environmental surveillance in the white continent.
HIGHLIGHTS
-Union Glacier soils host a microbial community dominated by bacteria, mainly from the phylum Actinomycetota.
-Archaea from the Nitrosocosmicus genus (family Nitrosphaeraceae) were ubiquitously detected.
-Although extreme and remote, these soils host multidrug-resistant and potentially pathogenic bacteria. Some were cultured and tested in vitro .
-Metagenomes and species-level representative genomes revealed diverse putative resistance and virulence genes.
-Part of the putative antimicrobial resistance genes and virulence factors could be associated with mobile elements in bacterial genomes.
... In fact, microorganisms inhabiting the Antarctic ice sheet may have evolved mechanisms to withstand sub-zero temperatures, low temperatures, high solar UV radiation, osmotic pressures, and limited nutrient availability [2,3]. Moreover, the harshest conditions characterizing the Polar Plateau makes this location a suitable analogue for some extraterrestrial conditions [4]; thus, untangling microbial diversity, inhabiting one of the most extreme environments on Earth, may inform us on the terrestrial habitability but also on the possibility of life elsewhere in the Solar System, particularly in the subsurface of icy worlds [5]. The present research is based on a recent study performed by Napoli and colleagues [6], which, in the frame of the BacFinder project (European Space Agency), aimed to explore the microbial diversity of the surface snow surrounding the Concordia Research Station and potential human contamination. ...
Simple Summary
The Antarctic Polar Plateau is one of the most extreme environments on Earth and our knowledge on the microbial diversity inhabiting this region is still limited. The BacFinder project investigated microbial diversity on the snow surface of the Polar Plateau, focusing on the vicinity of the Concordia Antarctic Research Station, to assess the microbial diversity and the potential impact of human presence on such a pristine environment. We found that seasonality was the main driver for both bacterial and fungal assemblages, while biodiversity appeared unaffected by distance from the base. Amplicon sequencing revealed a predominance of Basidiomycota (49%) and Ascomycota (42%) for the fungal component. Bacteroidota (65.8%) is the main representative of the bacterial component. Basidiomycetes are almost exclusively represented by yeast-like fungi. Overall, the study highlighted the impact of human activity on the microbial composition in this environment and may provide critical information on the habitability of extra-terrestrial analogs on our planet and on the possibility to explore the surfaces of icy worlds.
Abstract
The French–Italian Concordia Research Station, situated on the Antarctic Polar Plateau at an elevation of 3233 m above sea level, offers a unique opportunity to study the presence and variation of microbes introduced by abiotic or biotic vectors and, consequently, appraise the amplitude of human impact in such a pristine environment. This research built upon a previous work, which explored microbial diversity in the surface snow surrounding the Concordia Research Station. While that study successfully characterized the bacterial assemblage, detecting fungal diversity was hampered by the low DNA content. To address this knowledge gap, in the present study, we optimized the sampling by increasing ice/snow collected to leverage the final DNA yield. The V4 variable region of the 16S rDNA and Internal Transcribed Spacer (ITS1) rDNA was used to evaluate bacterial and fungal diversity. From the sequencing, we obtained 3,352,661 and 4,433,595 reads clustered in 930 and 3182 amplicon sequence variants (ASVs) for fungi and bacteria, respectively. Amplicon sequencing revealed a predominance of Basidiomycota (49%) and Ascomycota (42%) in the fungal component; Bacteroidota (65.8%) is the main representative among the bacterial phyla. Basidiomycetes are almost exclusively represented by yeast-like fungi. Our findings provide the first comprehensive overview of both fungal and bacterial diversity in the Antarctic Polar Plateau’s surface snow/ice near Concordia Station and to identify seasonality as the main driver of microbial diversity; we also detected the most sensitive microorganisms to these factors, which could serve as indicators of human impact in this pristine environment and aid in planetary protection for future exploration missions.
... Ascomycota usually have high relative abundance in soil fungal communities [49]. This phylum is regarded as a pollution indicator which display a greater environmental tolerance over anthropogenic contamination and thrives at high pollution loading environments [50]. The results in this study showed that the contamination of PFHxS had a positive influence on the abundance of Ascomycota in soil. ...
Per- and poly-fluoroalkyl substances (PFAS) have raised global concerns regarding soil contamination and the subsequent adverse effects on soil organisms. PFOS, PFOA, and PFHxS are among the commonly detected PFAS in the environment with much attention directed to PFOS and PFOA and minimal information available on the toxicity of PFHxS for ecotoxicological assessments. Therefore, this study focuses on the toxic potential of PFHxS to soil biota. The effects of PFHxS to microbial processes and earthworms were assessed in a wide range of concentration (0–1000 mg/kg) in soil to define the safe concentration. The soil enzyme activities (dehydrogenase activity and soil respiration rate) were significantly reduced after exposure to PFHxS at concentrations exceeding 100 mg/kg. The bacterial community suffered more than the fungal community upon PFHxS exposure. Bacterial diversity and richness were inhibited due to PFHxS exposure. However, at taxonomic level, growth of some bacterial phyla was stimulated (e.g., Actinobacteria) while others were inhibited (e.g., Acidobacteria). Earthworm survival was also significantly affected at concentrations exceeding 100 mg/kg. Our findings showed that exposure to PFHxS negatively affects the soil microbial processes and earthworm survival, potentially jeopardising their functions.
... Indeed, Mars analog fields are a reservoir of microorganisms used as models for understanding long-term survival and biomarker stability in habitable surface/subsurface environments on Mars (Martins et al., 2017). On Earth, due to the low temperature and extreme liquid water scarcity, the Dry Valleys in Antarctica and the Atacama Desert in Chile are considered the closest hyper-arid analogs of Mars (Cassaro et al., 2021;Azua-Bustos et al., 2022). Since on Earth the transition from arid to hyper-arid deserts causes a shift from edaphic communities to lithic communities and finally to communities in hygroscopic substrates, it is conceivable that, if life occurred on Mars, it may have withdrawn to subsurface environments (Davila and Schulze-Makuch, 2016). ...
The effect of a Mars-like UV flux and γ-radiation on the detectability of biomarkers in dried cells of Chroococcidiopsis sp. CCMEE 029 was investigated using a fluorescence sandwich microarray immunoassay. The production of anti-Chroococcidiopsis antibodies allowed the immunoidentification of a reduced, though still detectable, signal in dried cells mixed with phyllosilicatic and sulfatic Mars regolith simulants after exposure to 6.8 × 105 kJ/m2 of a Mars-like UV flux. No signal was detected in dried cells that were not mixed with minerals after 1.4 × 105 kJ/m2. For γ-radiation (60Co), no detectable variations of the fluorescence signal occurred in dried cells exposed to 113 kGy compared to non-irradiated dried cells. Our results suggest that immunoassay-based techniques could be used to detect life tracers eventually present in the martian subsurface in freshly excavated materials only if shielded from solar UV. The high structural integrity of biomarkers irradiated with γ-radiation that mimics a dose accumulated in 13 Myr at 2 m depth from the martian surface has implications for the potential detectability of similar organic molecules/compounds by future life-detection missions such as the ExoMars Rosalind Franklin rover.
... Due to the expensive and long-term dependent organization of space exploration, terrestrial analogs can serve as models for studies on the habitability of Mars, which has been a priority of Mars science investigations [5]. Generally, the terrestrial analogs on Earth are characterized by extreme environmental conditions, such as hyper-arid desert, saline or hypersaline habitat, thermal acidic spring, and cryogenic and dry Antarctica [9][10][11][12][13][14][15] Microbial composition and ecology in different Mars analogs have drawn attention due to their ecological and astrobiological importance. Microbiological studies in Mars analogs performed in the past decades have contributed to our better understanding of the strategy and spatiotemporal limit of life on Earth [16][17][18][19][20][21][22][23]. ...
The Qaidam Basin is the highest and one of the largest and driest deserts on Earth. It is considered a mars analog area in China. In contrast to numerous studies concerning its geology, geophysical, and chemistry, relatively few studies have reported microbial diversity and distribution in this area. Here, we investigated culturable yeast diversity in the northeast Qaidam Basin. A total of 194 yeast strains were isolated, and 12 genera and 21 species were identified, among which 19 were basidiomycetous yeasts. Naganishia albida, N. adeliensis, and Filobasidium magnum were the three most dominant species and were distributed in thirteen samples from eight locations. Five new species (Filobasidium chaidanensis, Kondoa globosum, Symmetrospora salmoneus, Teunia nitrariae, and Vishniacozyma pseudodimennae) were found and described based on ITS and D1D2 gene loci together with phenotypic characteristics and physiochemical analysis. Representative strains from each species were chosen for the salt-tolerant test, in which species showed different responses to different levels of NaCl concentrations. Further, the strain from soil can adapt well to the higher salt stress compared to those from plants or lichens. Our study represents the first report of the yeast diversity in the Qaidam Basin, including five new species, and also provides further information on the halotolerance of yeasts from the saline environment in mars analog.
... The evaluation of the stability/degradation of organics in conditions similar to those experienced beyond Earth's magnetic field protection, is of outmost importance to support the in situ life-detection missions. Among the microorganisms and biomolecules tested in the STARLIFE project, we have chosen the cryptoendolithic black fungus Cryomyces antarcticus, isolated from McMurdo Dry Valleys (Antarctica), one of the best terrestrial analogues of the Martian environment (Cassaro et al., 2021a). ...
The question about the stability of certain biomolecules is directly connected to the life-detection missions aiming to search for past or present life beyond Earth. The extreme conditions experienced on extraterrestrial planet surface ( e.g. Mars), characterized by ionizing and non-ionizing radiation, CO 2 -atmosphere and reactive species, may destroy the hypothetical traces of life. In this context, the study of the biomolecules behaviour after ionizing radiation exposure could provide support for the onboard instrumentation and data interpretation of the life exploration missions on other planets. Here, as a part of STARLIFE campaign, we investigated the effects of gamma rays on two classes of fungal biomolecules–nucleic acids and melanin pigments – considered as promising biosignatures to search for during the ‘ in situ life-detection’ missions beyond Earth.
... Establishing continuous, systematic, long-term, and spatially adequate monitoring of this remote and harsh setting is very challenging (Sanderson, 2010). Directly monitoring Antarctica has been likened to surveying and monitoring extra-terrestrial planetary conditions (Barthels, 2020;Cassaro et al., 2021;Page, 2019;Salvatore & Levy, 2021;Sassenroth et al., 2021). Although polar environments are home to unique ecosystems, have high conservation value, and are vital for regulating global climate (British Antarctic Survey, 2017;Meredith et al., 2019;National Aeronautics and Space Administration, 2021;Norwegian Polar Institute, 2021), only a fraction has been invested in Antarctic research compared to the amount of money invested in past Mars missions (McCarthy, 2021). ...
Monitoring and understanding Antarctica is critical for conservation of its values. Remote sensing has been increasingly employed to observe large areas at higher frequency than traditional monitoring methods, enabling systematic assessments at low cost. However, currently there are limitations in the ability of the available remote sensing tools to answer the most pressing scientific, ecological, and biological questions associated with anthropogenic impacts, including climate change, in Antarctica. Here we summarise the latest findings on remote sensing tools and techniques, identifying the gaps and highlighting priority areas for future development. Major ongoing challenges concern the intensive cloud coverage and ephemeral snow cover that prevent ongoing observations of ice-free areas and the fine spatial scales required to undertake assessments of terrestrial ecosystems, their biota, and the human footprint. Opportunities arise in the realms of advanced statistical techniques to harness the potential of increasingly available data from orbital satellites and Unmanned Aerial Systems also commonly known as drones, at multiple scales and resolutions. We conclude that harnessing emerging technological advances in remote sensing will enable new understanding and ultimately protection of Antarctic ecosystems.
... The features of the Antarctic terrestrial environment are characterized by high ultraviolet radiation, freezing, and extreme dryness (Perera-Castro et al., 2020;Cassaro et al., 2021). Notably, the strong ultraviolet radiation in Antarctica is a typical consequence of global climate change and human activities. ...
The Antarctic continent has extreme natural environment and fragile ecosystem. Mosses are one of the dominant floras in the Antarctic continent. However, their genomic features and adaptation processes to extreme environments remain poorly understood. Here, we assembled the high-quality genome sequence of the Antarctic moss (Pohlia nutans) with 698.20 Mb and 22 chromosomes. We found that the high proportion of repeat sequences and a recent whole-genome duplication (WGD) contribute to the large size genome of P. nutans when compared to other bryophytes. The genome of P. nutans harbors the signatures of massive segmental gene duplications and large expansions of gene families, likely facilitating neofunctionalization. Genomic characteristics that may support the Antarctic lifestyle of this moss comprise expanded gene families involved in phenylpropanoid biosynthesis, unsaturated fatty acid biosynthesis, and plant hormone signal transduction. Additional contributions include the significant expansion and upregulation of several genes encoding DNA photolyase, antioxidant enzymes, flavonoid biosynthesis enzymes, possibly reflecting diverse adaptive strategies. Notably, integrated multi-omic analyses elucidate flavonoid biosynthesis may function as the reactive oxygen species detoxification under UV-B radiation. Our studies provide insight into the unique features of the Antarctic moss genome and their molecular responses to extreme terrestrial environments.
... Here, the endurance of biomolecules of the extremotolerant fungus Cryomyces antarcticus after the exposure to the ground-based Science Verification Tests (SVTs), conducted in preparation for the flight mission EXPOSE-R2 as part of the Biology and Mars Experiment (BIOMEX) project (Rabbow et al., 2012(Rabbow et al., , 2015 were analysed through a metabolomic approach. The ESA's BIOMEX project aimed to investigate the (i) survivability of the selected extremophilic organisms and (ii) stability/degradation of biomolecules under simulated Martian and space conditions and into low Earth orbit (LEO;de Vera et al., 2012de Vera et al., , 2019. Previous works reported the capability of C. antarcticus to tolerate different kinds of stressors (Onofri et al., 2007;Pacelli et al., 2017aPacelli et al., ,b,c, 2019Pacelli et al., , 2021Aureli et al., 2020;Cassaro et al., 2021) and to resist in real space (Onofri et al., 2012) under simulated Martian conditions for 1.5 years in LEO (Onofri et al., 2015). ...
... The ESA's BIOMEX project aimed to investigate the (i) survivability of the selected extremophilic organisms and (ii) stability/degradation of biomolecules under simulated Martian and space conditions and into low Earth orbit (LEO;de Vera et al., 2012de Vera et al., , 2019. Previous works reported the capability of C. antarcticus to tolerate different kinds of stressors (Onofri et al., 2007;Pacelli et al., 2017aPacelli et al., ,b,c, 2019Pacelli et al., , 2021Aureli et al., 2020;Cassaro et al., 2021) and to resist in real space (Onofri et al., 2012) under simulated Martian conditions for 1.5 years in LEO (Onofri et al., 2015). Survivability studies conducted after SVTs treatments, reported a good metabolic activity and growth rate without significant DNA or ultrastructural damages (Pacelli et al., 2019). ...
The identification of traces of life beyond Earth (e.g., Mars, icy moons) is a challenging task because terrestrial chemical-based molecules may be destroyed by the harsh conditions experienced on extraterrestrial planetary surfaces. For this reason, studying the effects on biomolecules of extremophilic microorganisms through astrobiological ground-based space simulation experiments is significant to support the interpretation of the data that will be gained and collected during the ongoing and future space exploration missions. Here, the stability of the biomolecules of the cryptoendolithic black fungus Cryomyces antarcticus, grown on two Martian regolith analogues and on Antarctic sandstone, were analysed through a metabolomic approach, after its exposure to Science Verification Tests (SVTs) performed in the frame of the European Space Agency (ESA) Biology and Mars Experiment (BIOMEX) project. These tests are building a set of ground-based experiments performed before the space exposure aboard the International Space Station (ISS). The analysis aimed to investigate the effects of different mineral mixtures on fungal colonies and the stability of the biomolecules synthetised by the fungus under simulated Martian and space conditions. The identification of a specific group of molecules showing good stability after the treatments allow the creation of a molecular database that should support the analysis of future data sets that will be collected in the ongoing and next space exploration missions.
... On the other hand, cells and products of their vital activity, found in the cryosphere of the Earth, represent a possible analogue of extraterrestrial ecosystems. If life existed in the early stages of the development of the planets, it is likely that its traces will be preserved in alien cryolitic zone and ice sheets of heavenly bodies [4,5]. ...
