Special Issue "Astrobiology and Microorganisms: Life to the Extreme, on Earth and Beyond"

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Environmental Microbiology".

Deadline for manuscript submissions: closed (31 December 2021).

Special Issue Editors

Dr. Paola Di Donato
E-Mail Website
Guest Editor
Department of Science and Technology, Parthenope University of Naples, Centro Direzionale Isola C4, 80143 Napoli, Italy
Interests: biochemistry; microorganisms in extreme conditions; planetary field analogues
Dr. Annarita Poli
E-Mail Website
Guest Editor
Institute of Biomolecular Chemistry, National Research Council of Italy -Via Campi Flegrei, 34, (80078) Pozzuoli (NA), Italy
Interests: astrobiology; extremophiles; taxonomy of extremophiles

Special Issue Information

Dear Colleagues,

Astrobiology is the multidisciplinary approach to the investigation of origin, development, and future of life in the Universe. Many studies in Astrobiology point at microorganisms, both prokaryotic and eukaryotic, since they are likely to have been the first forms of life on Earth; moreover, most of them have adapted to living in extreme environments that are considered as “planetary field analogues”, i.e., sites whose chemical and physical conditions partly resemble those of other planetary bodies in the Solar System.

The study of microorganisms represents a powerful tool to answer some key questions in Astrobiology, spanning from the identification of life forms that could adapt to living in space and potentially colonizing other planets, to the prevention of the planetary contamination that can occur as a consequence of space missions.

Papers dealing with the identification of new microbial life forms from extreme environments that can be considered as planetary field analogues, the investigation of the response of microorganisms to real or simulated space conditions, the study of the strategies and mechanisms by which microorganisms survive to extreme conditions resembling those of space and/or exoplanets, and the search for tools to prevent contamination of spacecraft assembly facilities will be considered for this Special Issue.

Prof. Paola Di Donato
Guest Editor

Manuscript Submission Information

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Keywords

  • astrobiology
  • new microbial life forms
  • microorganisms in extreme conditions

Published Papers (6 papers)

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Research

Article
Effects of Ionizing Radiation and Long-Term Storage on Hydrated vs. Dried Cell Samples of Extremophilic Microorganisms
Microorganisms 2022, 10(1), 190; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10010190 - 16 Jan 2022
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Abstract
A main factor hampering life in space is represented by high atomic number nuclei and energy (HZE) ions that constitute about 1% of the galactic cosmic rays. In the frame of the “STARLIFE” project, we accessed the Heavy Ion Medical Accelerator (HIMAC) facility [...] Read more.
A main factor hampering life in space is represented by high atomic number nuclei and energy (HZE) ions that constitute about 1% of the galactic cosmic rays. In the frame of the “STARLIFE” project, we accessed the Heavy Ion Medical Accelerator (HIMAC) facility of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. By means of this facility, the extremophilic species Haloterrigena hispanica and Parageobacillus thermantarcticus were irradiated with high LET ions (i.e., Fe, Ar, and He ions) at doses corresponding to long permanence in the space environment. The survivability of HZE-treated cells depended upon either the storage time and the hydration state during irradiation; indeed, dry samples were shown to be more resistant than hydrated ones. With particular regard to spores of the species P. thermantarcticus, they were the most resistant to irradiation in a water medium: an analysis of the changes in their biochemical fingerprinting during irradiation showed that, below the survivability threshold, the spores undergo to a germination-like process, while for higher doses, inactivation takes place as a consequence of the concomitant release of the core’s content and a loss of integrity of the main cellular components. Overall, the results reported here suggest that the selected extremophilic microorganisms could serve as biological model for space simulation and/or real space condition exposure, since they showed good resistance to ionizing radiation exposure and were able to resume cellular growth after long-term storage. Full article
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Article
Potential of Acidithiobacillus ferrooxidans to Grow on and Bioleach Metals from Mars and Lunar Regolith Simulants under Simulated Microgravity Conditions
Microorganisms 2021, 9(12), 2416; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9122416 - 23 Nov 2021
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Abstract
The biomining microbes which extract metals from ores that have been applied in mining processes worldwide hold potential for harnessing space resources. Their cell growth and ability to extract metals from extraterrestrial minerals under microgravity environments, however, remains largely unknown. The present study [...] Read more.
The biomining microbes which extract metals from ores that have been applied in mining processes worldwide hold potential for harnessing space resources. Their cell growth and ability to extract metals from extraterrestrial minerals under microgravity environments, however, remains largely unknown. The present study used the model biomining bacterium Acidithiobacillus ferrooxidans to extract metals from lunar and Martian regolith simulants cultivated in a rotating clinostat with matched controls grown under the influence of terrestrial gravity. Analyses included assessments of final cell count, size, morphology, and soluble metal concentrations. Under Earth gravity, with the addition of Fe3+ and H2/CO2, A. ferrooxidans grew in the presence of regolith simulants to a final cell density comparable to controls without regoliths. The simulated microgravity appeared to enable cells to grow to a higher cell density in the presence of lunar regolith simulants. Clinostat cultures of A. ferrooxidans solubilised higher amounts of Si, Mn and Mg from lunar and Martian regolith simulants than abiotic controls. Electron microscopy observations revealed that microgravity stimulated the biosynthesis of intracellular nanoparticles (most likely magnetite) in anaerobically grown A. ferrooxidans cells. These results suggested that A. ferrooxidans has the potential for metal bioleaching and the production of useful nanoparticles in space. Full article
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Article
The Abundance and Taxonomic Diversity of Filterable Forms of Bacteria during Succession in the Soils of Antarctica (Bunger Hills)
Microorganisms 2021, 9(8), 1728; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9081728 - 13 Aug 2021
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Abstract
Previous studies have shown that a significant part of the bacterial communities of Antarctic soils is represented by cells passing through filters with pore sizes of 0.2 µm. These results raised new research questions about the composition and diversity of the filterable forms [...] Read more.
Previous studies have shown that a significant part of the bacterial communities of Antarctic soils is represented by cells passing through filters with pore sizes of 0.2 µm. These results raised new research questions about the composition and diversity of the filterable forms of bacteria (FFB) in Antarctic soils and their role in the adaptation of bacteria to the extreme living conditions. To answer such questions, we analyzed the succession of bacterial communities during incubation of Antarctic soil samples from the Bunger Hills at increased humidity and positive temperatures (5 °C and 20 °C). We determined the total number of viable cells by fluorescence microscopy in all samples and assessed the taxonomic diversity of bacteria by next-generation sequencing of the 16S rRNA gene region. Our results have shown that at those checkpoints where the total number of cells reached the maximum, the FFB fraction reached its minimum, and vice versa. We did not observe significant changes in taxonomic diversity in the soil bacterial communities during succession. During our study, we found that the soil bacterial communities as a whole and the FFB fraction consist of almost the same phylogenetic groups. We suppose rapid transition of the cells of the active part of the bacterial population to small dormant forms is one of the survival strategies in extreme conditions and contributes to the stable functioning of microbial communities in Antarctic soils. Full article
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Article
Microbial Hotspots in Lithic Microhabitats Inferred from DNA Fractionation and Metagenomics in the Atacama Desert
Microorganisms 2021, 9(5), 1038; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9051038 - 12 May 2021
Cited by 3 | Viewed by 1361
Abstract
The existence of microbial activity hotspots in temperate regions of Earth is driven by soil heterogeneities, especially the temporal and spatial availability of nutrients. Here we investigate whether microbial activity hotspots also exist in lithic microhabitats in one of the most arid regions [...] Read more.
The existence of microbial activity hotspots in temperate regions of Earth is driven by soil heterogeneities, especially the temporal and spatial availability of nutrients. Here we investigate whether microbial activity hotspots also exist in lithic microhabitats in one of the most arid regions of the world, the Atacama Desert in Chile. While previous studies evaluated the total DNA fraction to elucidate the microbial communities, we here for the first time use a DNA separation approach on lithic microhabitats, together with metagenomics and other analysis methods (i.e., ATP, PLFA, and metabolite analysis) to specifically gain insights on the living and potentially active microbial community. Our results show that hypolith colonized rocks are microbial hotspots in the desert environment. In contrast, our data do not support such a conclusion for gypsum crust and salt rock environments, because only limited microbial activity could be observed. The hypolith community is dominated by phototrophs, mostly Cyanobacteria and Chloroflexi, at both study sites. The gypsum crusts are dominated by methylotrophs and heterotrophic phototrophs, mostly Chloroflexi, and the salt rocks (halite nodules) by phototrophic and halotolerant endoliths, mostly Cyanobacteria and Archaea. The major environmental constraints in the organic-poor arid and hyperarid Atacama Desert are water availability and UV irradiation, allowing phototrophs and other extremophiles to play a key role in desert ecology. Full article
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Article
A Weakened Immune Response to Synthetic Exo-Peptides Predicts a Potential Biosecurity Risk in the Retrieval of Exo-Microorganisms
Microorganisms 2020, 8(7), 1066; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8071066 - 17 Jul 2020
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Abstract
The discovery of liquid water at several locations in the solar system raises the possibility that microbial life may have evolved outside Earth and as such could be accidently introduced into the Earth’s ecosystem. Unusual sugars or amino acids, like non-proteinogenic isovaline and [...] Read more.
The discovery of liquid water at several locations in the solar system raises the possibility that microbial life may have evolved outside Earth and as such could be accidently introduced into the Earth’s ecosystem. Unusual sugars or amino acids, like non-proteinogenic isovaline and α-aminoisobutyric acid that are vanishingly rare or absent from life forms on Earth, have been found in high abundance on non-terrestrial carbonaceous meteorites. It is therefore conceivable that exo-microorganisms might contain proteins that include these rare amino acids. We therefore asked whether the mammalian immune system would be able to recognize and induce appropriate immune responses to putative proteinaceous antigens that include these rare amino acids. To address this, we synthesised peptide antigens based on a backbone of ovalbumin and introduced isovaline and α-aminoisobutyric acid residues and demonstrated that these peptides can promote naïve OT-I cell activation and proliferation, but did so less efficiently than the canonical peptides. This is relevant to the biosecurity of missions that may retrieve samples from exoplanets and moons that have conditions that may be permissive for life, suggesting that accidental contamination and exposure to exo-microorganisms with such distinct proteomes might pose an immunological challenge. Full article
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Article
Limited Response of Indigenous Microbes to Water and Nutrient Pulses in High-Elevation Atacama Soils: Implications for the Cold–Dry Limits of Life on Earth
Microorganisms 2020, 8(7), 1061; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms8071061 - 16 Jul 2020
Cited by 1 | Viewed by 1059
Abstract
Soils on the world’s highest volcanoes in the Atacama region represent some of the harshest ecosystems yet discovered on Earth. Life in these environments must cope with high UV flux, extreme diurnal freeze–thaw cycles, low atmospheric pressure and extremely low nutrient and water [...] Read more.
Soils on the world’s highest volcanoes in the Atacama region represent some of the harshest ecosystems yet discovered on Earth. Life in these environments must cope with high UV flux, extreme diurnal freeze–thaw cycles, low atmospheric pressure and extremely low nutrient and water availability. Only a limited spectrum of bacterial and fungal lineages seems to have overcome the harshness of this environment and may have evolved the ability to function in situ. However, these communities may lay dormant for most of the time and spring to life only when enough water and nutrients become available during occasional snowfalls and aeolian depositions. We applied water and nutrients to high-elevation soils (5100 meters above sea level) from Volcán Llullaillaco, both in lab microcosms and in the field, to investigate how microbial communities respond when resource limitations are alleviated. The dominant taxon in these soils, the extremophilic yeast Naganishia sp., increased in relative sequence abundance and colony-forming unit counts after water + nutrient additions in microcosms, and marginally in the field after only 6 days. Among bacteria, only a Noviherbaspirillum sp. (Oxalobacteraceae) significantly increased in relative abundance both in the lab and field in response to water addition but not in response to water and nutrients together, indicating that it might be an oligotroph uniquely suited to this extreme environment. The community structure of both bacteria and eukaryotes changed significantly with water and water + nutrient additions in the microcosms and taxonomic richness declined with amendments to water and nutrients. These results indicate that only a fraction of the detected community is able to become active when water and nutrients limitations are alleviated in lab microcosms, and that water alone can dramatically change community structure. Our study sheds light on which extremophilic organisms are likely to respond when favorable conditions occur in extreme earthly environments and perhaps in extraterrestrial environments as well. Full article
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