Antarctica as a reservoir of planetary analogue environments

Biomarker Preservation in Antarctic Sandstones after Prolonged Space Exposure Outside the International Space Station During the ESA EXPOSE-E Lichens and Fungi Experiment

A primary aim of current and future space exploration missions is the detection and identification of chemical and biological indicators of life, namely biomarkers, on Mars. The Mars Sample Return NASA-ESA program will bring to Earth samples of martian soil, acquired from up to 7 cm depth. The ESA Rosalind Franklin rover will search for signs of life in the subsurface (down to a depth of 2 meters), given the highly radioactive conditions on Mars' surface, which are not ideal for life as we know it and for the preservation of its traces. In the frame of the Lichens and Fungi Experiment, small fragments of Antarctic sandstones colonized by cryptoendolithic microbial communities were exposed to space and simulated martian conditions in low Earth orbit for 18 months, aboard the EXPOSE-E payload. Through the use of Raman and infrared spectroscopies, as well as a metabolomic approach, we aimed to detect organic compounds in a quartz mineral matrix. The results show that pigments, such as melanin, carotenoids, and chlorophyll, lipids, and amino acids, maintained their stability within minerals under simulated martian conditions in space, which makes them ideal biomarkers for the exploration of putative life on Mars.

The Antarctic moss 2-oxoglutarate/Fe(II)-dependent dioxygenases (Pn2-ODD2) enhanced the tolerance to drought and oxidative stress

BACKGROUND

Flavonoid biosynthesis pathway is generally thought unique to land plants and has assisted plants to adapt the terrestrial ecosystems. In this pathway, four 2-oxoglutarate/Fe(II)-dependent dioxygenases (2-ODDs), i.e., flavone synthase I (FNSI), flavanone-3-hydroxylase (F3H), flavonol synthase (FLS) and anthocyanin synthase/leucoanthocyanidin dioxygenase (ANS/LDOX), catalyze the hydroxylation and desaturation reactions. In bryophytes, the earliest land plant group, little is known about the biological functions of these enzymes.

RESULTS

Here, we cloned a Pn2-ODD2 gene of flavonoid biosynthesis pathway from Antarctic moss Pohlia nutans, which was induced by exogenous NaCl, PEG and abscisic acid (ABA) treatment. Overexpression of Pn2-ODD2 increased the drought resistance in Physcomitrium patens and Arabidopsis thaliana during gametophyte growth and seed germination, respectively. Overexpressed-Pn2-ODD2 Arabidopsis also exhibited the enhanced tolerance to oxidative stress, with the downregulation of ROS generation gene and increased the total flavonoid content. Also, overexpression of Pn2-ODD2 decreased the ABA sensitivity in transgenic P. patens and Arabidopsis. Meanwhile, overexpression of Pn2-ODD2 resulted in an increase in both anthocyanins and flavonols in Arabidopsis, which was correlated with the up-regulated anthocyanin biosynthesis gene.

CONCLUSIONS

Taken together, Pn2-ODD2 conferred the resistance to drought and oxidative stress by regulating antioxidant defense system in plants.

Adaptation of the psychrophilic Mucor psychrophilus (Mucorales, Mucoromycota) to lower temperatures and under conditions of heat and osmotic shocks

The definitions of psychrophilia and psychrotolerance are based on the optimal temperature of growth (≤15 and 20 °C, respectively), and it is not clear whether differences exist in adaptation mechanisms. We analyzed the composition of osmolytes and membrane lipids of a true psychrophile Mucor psychrophilus during submerged cultivation at 12.5 °C and 4 °C, as well as under heat and osmotic shocks. The main osmolyte at 12.5 °C is trehalose (70 % of the total), whereas at 4 °C, comparable proportions of glycerol, glucose, and trehalose are observed. Under heat shock, the amount of trehalose increases threefold, and osmotic shock leads to an increase of the glycerol level without a reduction in the amount of trehalose. The predominant membrane lipids at both temperatures are non-bilayer phosphatidic acids (about 65 % of the sum) and phosphatidylethanolamines (20-30 %). An increase in the degree of unsaturation and a decrease in the sterols proportion are observed during growth at 4 °C, whereas at 12.5 °C, as well as under heat and osmotic shocks, the changes are insignificant. Similarity of the adaptation mechanisms of the psychrophilic and psychrotolerant fungi indicates the ambiguity of psychrophilia and psychrotolerance definitions.

An astrobiological perspective on microbial biofilms: their importance for habitability and production of detectable and lasting biosignatures

The search for life elsewhere in the universe has remained one of the main goals of astrobiological exploration. In this quest, extreme environments on Earth have served as analogs to study the potential habitability of Mars and icy moons, which include but are not limited to hydrothermal vent systems, acid lakes, deserts, and polar ice, among others. Within the various forms that life manifests, biofilms constitute one of the most widespread phenotypes and are ubiquitous in extreme environments. Biofilms are structured communities of microorganisms enclosed in a matrix of extracellular polymeric substances (EPS) that protect against unfavorable and dynamic conditions. These concentrated structures and their associated chemistry may serve as unique and persistent signatures of life processes that may aid in their detection. Here we propose biofilms as a model system to understand the habitability of extraterrestrial systems and as sources of recognizable and persistent biosignatures for life detection. By testing these ideas in extreme analog environments on Earth, this approach could be used to guide and focus future exploration of samples encompassing the geologic record of early Earth as well as other planets and moons of our solar system.

Advocating microbial diversity conservation in Antarctica

Antarctica, a seemingly barren and icy wilderness, is home to a diverse array of microbial life that plays a critical role in sustaining its ecosystems. These resilient microorganisms drive nutrient cycling and carbon sequestration, but their function in global processes remains unclear. This pristine environment faces mounting threats from human activities, climate change, and increasing tourism. Contaminants, non-native species, and microplastics are increasingly reaching even the most remote regions, disrupting delicate microbial communities existing for millions of years. Antarctic microorganisms are not only ecologically significant but also valuable for biotechnological advancements, making their conservation imperative. Climate change exacerbates these threats, altering microbial habitats and promoting shifts in community structure. Tourism growth, though beneficial for education and economic reasons, poses significant challenges through biological and chemical contamination. Despite efforts under the Antarctic Treaty System to protect the region, there is a critical need for enhanced measures specifically targeting microbial conservation. This article underscores the importance of conserving Antarctic microbial diversity. It highlights the intricate microbial ecosystems and the urgency of implementing strategies such as stringent biosecurity measures, sustainable tourism practices, and comprehensive monitoring programs. Additionally, fostering international collaboration and research initiatives is vital for understanding and designing strategies to mitigate the impacts of environmental changes on microbial life. By prioritizing microbial conservation in policy frameworks and strengthening global cooperation, we can safeguard these unique ecosystems and ensure their resilience for future generations.

Comparative omics directed gene discovery and rewiring for normal temperature-adaptive red pigment synthesis by polar psychrotrophic fungus Geomyces sp. WNF-15A

The Antarctic fungus Geomyces sp. WNF-15A can produce high-quality red pigments (AGRP) with good prospects for the use in food and cosmetic area. However, efficient AGRP synthesis relies on low-temperature and thus limits its industrial development. Here genome sequencing and comparative analysis were performed on the wild-type versus to four mutants derived from natural mutagenesis and transposon insertion mutation. Eleven mutated genes were identified from 2309 SNPs and 256 Indels. A CRISPR-Cas9 gene-editing system was established for functional analysis of these genes. Deficiency of scaffold1.t692 and scaffold2.t704 with unknown functions highly improved AGRP synthesis at all tested temperatures. Of note, the two mutants produced comparable levels of AGRP at 20 °C to the wild-type at 14 °C. They also broke the normal-temperature limitation and effectively synthesized AGRP at 25 °C. Comparative metabolomic analysis revealed that deficiency of scaffold1.t692 improved AGRP synthesis by regulation of global metabolic pathways especially downregulation of the competitive pathways. Knockout of key genes responsible for the differential metabolites confirmed the metabolomic results. This study shows new clues for cold-adaptive regulatory mechanism of polar fungi. It also provides references for exploitation and utilization of psychrotrophic fungal resources.

"Monitoring inflammatory, immune system mediators, and mitochondrial changes related to brain metabolism during space flight"

The possibility of impaired cognitive function during deep space flight missions or while living on a Martian colony is a critical point of concern and pleads for further research. In addition, a fundamental gap exists both in our understanding and application of countermeasures for the consequences of long duration space travel and/or living in an extreme environment such as on the Moon or Mars. Previous studies, while heavily analyzing pre- and post-flight conditions, mostly fail to appreciate the cognitive stressors associated with space radiation, microgravity, confinement, hostile or closed environments, and the long distances from earth. A specific understanding of factors that affect cognition as well as structural and/or physiological changes in the brains of those on a space mission in addition to new countermeasures should result in improved health of our astronauts and reduce risks. At the core of cognitive changes are mechanisms we typically associate with aging, such as inflammatory responses, changes in brain metabolism, depression, and memory impairments. In fact, space flight appears to accelerate aging. In this review, we will discuss the importance of monitoring inflammatory and immune system mediators such as nuclear factor kappa B (NF-κB), and mitochondrial changes related to brain metabolism. We conclude with our recommended countermeasures that include pharmacological, metabolic, and nutritional considerations for the risks on cognition during space missions.

A preliminary survey of the cellular responses of the black fungus Cryomyces antarcticus to long and short-term dehydration

The McMurdo Dry Valleys in Southern Victoria Land, Antarctica, are known for their extreme aridity, cold, and nutrient-poor conditions. These valleys provide a valuable comparison to environments on Mars. The survival of microorganisms in these areas hinges on their ability to withstand dehydration due to the limited availability of liquid water. Some microorganisms have adapted to survive extended periods of metabolic inactivity and dehydration, a physiological response to the harsh conditions in which they exist. This adaptation is significant for astrobiology studies as it allows for testing the resilience of microorganisms under extraterrestrial conditions, exploring the boundaries and potential for life beyond Earth. In this study, we examined the survivability, metabolic activity, cellular membrane integrity, and ultrastructural damage of Cryomyces antarcticus, a eukaryotic organism used for astrobiological studies, following two dehydration processes. We conducted a fast dehydration process, simulating what happens on the surface of Antarctic rocks under typical environmental conditions, and a slow dehydration process, which is commonly used in astrobiological experiments. Our findings revealed a higher percentage of damaged cells following slow dehydration treatments, confirming that rapid dehydration reflects the adaptability of microorganisms to respond to sudden and drastic changes in the Antarctic environment.

Active microbiota persist in dry permafrost and active layer from Elephant Head, Antarctica

Dry permafrost is a challenging environment for microbial life due to cold, dry, and often oligotrophic conditions. In 2016, Elephant Head, Antarctica, was confirmed as the second site on Earth to contain dry permafrost. It is geographically distinct from the McMurdo Dry Valleys where dry permafrost has been studied previously. Here, we present the first study of the microbial activity, diversity, and functional potential of Elephant Head dry permafrost. Microbial activity was measured using radiorespiration assays with radiolabeled acetate as a carbon source at 5, 0, and -5°C. Low, but detectable, rates of microbial activity were measured in some samples at 0 and -5°C. This is distinct from previous studies of McMurdo Dry Valley dry permafrost which concluded that dry permafrost represents a cold-arid limit to life on the planet. The isolation of cold-adapted organisms from these soils, including one capable of subzero growth, further supports that the Elephant Head dry active layer and dry permafrost harbor viable microbial life, which may be active in situ. Metagenomic, 16S rRNA gene, and internal transcribed spacer and amplicon sequencing identified similar microbial communities to other Antarctic and cold environments. The Elephant Head microbial community appears to be adapted for survival in cold, dry, and oligotrophic conditions based on the presence of cold adaptation and stress response genes in the metagenomes. Together, our results show that dry permafrost environments do not exclude active microbial life at subzero temperatures, suggesting that the cold, dry soils of Mars may also not be as inhospitable as previously thought.

Metabolic versatility of soil microbial communities below the rocks of the hyperarid Dalangtan Playa

IMPORTANCE

The hyperarid Dalangtan Playa in the western Qaidam Basin, northwestern China, is a unique terrestrial analog of Mars. Despite the polyextreme environments of this area, habitats below translucent rocks capable of environmental buffering could serve as refuges for microbial life. In this study, the hybrid assembly of Illumina short reads and Nanopore long reads recovered high-quality and high-continuity genomes, allowing for high-accuracy analysis and a deeper understanding of extremophiles in the sheltered soils of the Dalangtan Playa. Our findings reveal self-supporting and metabolically versatile sheltered soil communities adapted to a hyperarid and hypersaline playa, which provides implications for the search for life signals on Mars.

Seasonality Is the Main Determinant of Microbial Diversity Associated to Snow/Ice around Concordia Station on the Antarctic Polar Plateau

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.

Survival, metabolic activity, and ultrastructural damages of Antarctic black fungus in perchlorates media

Evidence from recent Mars landers identified the presence of perchlorates salts at 1 wt % in regolith and their widespread distribution on the Martian surface that has been hypothesized as a critical chemical hazard for putative life forms. However, the hypersaline environment may also potentially preserve life and its biomolecules over geological timescales. The high concentration of natural perchlorates is scarcely reported on Earth. The presence of perchlorates in soil and ice has been recorded in some extreme environments including the McMurdo Dry Valleys in Antarctica, one of the best terrestrial analogues for Mars. In the frame of "Life in space" Italian astrobiology project, the polyextremophilic black fungus Cryomyces antarcticus, a eukaryotic test organism isolated from the Antarctic cryptoendolithic communities, has been tested for its resistance, when grown on different hypersaline substrata. In addition, C. antarcticus was grown on Martian relevant perchlorate medium (0.4 wt% of Mg(ClO4)2 and 0.6 wt% of Ca(ClO4)2) to investigate the possibility for the fungus to survive in Martian environment. Here, the results indicate a good survivability and metabolic activity recovery of the black fungus when grown on four Martian relevant perchlorates. A low percentage of damaged cellular membranes have been found, confirming the ultrastructural investigation.

Mars-like UV Flux and Ionizing Radiation Differently Affect Biomarker Detectability in the Desert Cyanobacterium Chroococcidiopsis as Revealed by the Life Detector Chip Antibody Microarray

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.

Yeast Diversity in the Qaidam Basin Desert in China with the Description of Five New Yeast Species

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.

Naturally low biodiversity is getting a raw deal in the media

While media usage has helped biodiversity gain a central spot in the contemporary conservation landscape, it is acknowledged that high biodiversity in itself is not always the best indication of conservation value. There are multiple reasons why low-biodiversity systems have to be valued. Such systems are easier to appreciate by the general public in their entirety, and also easier to study, with most model systems referring to low numbers of species. In remote and environmentally harsh settings, biodiversity can increase via biological invasion, which is usually perceived as a negative anthropogenic impact. Island systems, typically lower in biodiversity compared to continental settings, are, specifically thanks to the available niche space, laboratories of speciation and potentially macroevolutionary innovation. Although biodiversity hotspots are at the centre of global conservation efforts, coldspots have their own dynamics and conservation needs, generally poorly understood at this stage due to the high-biodiversity focus. Here, I discuss the media relevance and, where applicable, distortion, of these aspects. I conclude by recommending a local rather than global focus in the marketing of conservation, which could encourage an appreciation of naturally low biodiversity.

Metabolomic Profile of the Fungus Cryomyces antarcticus Under Simulated Martian and Space Conditions as Support for Life-Detection Missions on Mars

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.

Investigation of fungal biomolecules after Low Earth Orbit exposure: a testbed for the next Moon missions

The Moon is characterized by extremely harsh conditions due to ultraviolet irradiation, wide temperature extremes, vacuum resulting from the absence of an atmosphere and high ionizing radiation. Therefore, its surface may provide a unique platform to investigate the effects of such conditions. For lunar exploration with the Lunar Gateway platform, exposure experiments in Low Earth Orbit are useful testbeds to prepare for lunar space experiments and to understand how and if potential biomarkers are influenced by extra‐terrestrial conditions. During the BIOMEX (BIOlogy and Mars EXperiment) project, dried colonies of the fungus Cryomyces antarcticus grown on Lunar Regolith Analogue (LRA) were exposed to space conditions for 16 months aboard the EXPOSE‐R2 payload outside the International Space Station. In this study, we investigated the stability/degradation of fungal biomarkers in LRA after exposure to (i) simulated space and (ii) real space conditions, using Raman spectroscopy, gas chromatography–mass spectrometry and DNA amplification. The results demonstrated that fungal biomarkers were detectable after 16 months of real space exposure. This work will contribute to the interpretation of data from future biological experiments in the Cislunar orbit with the Lunar Gateway platform and/or on the lunar surface, in preparation for the next step of human exploration.

The Antarctic Moss Pohlia nutans Genome Provides Insights Into the Evolution of Bryophytes and the Adaptation to Extreme Terrestrial Habitats

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.