Taxonomic and functional analyses of intact microbial communities thriving in extreme, astrobiology-relevant, anoxic sites

Background: Extreme terrestrial, analogue environments are widely used models to study the limits of life and to infer habitability of extraterrestrial settings. In contrast to Earth’s ecosystems, potential extraterrestrial biotopes are usually characterized by a lack of oxygen. Methods: In the MASE project (Mars Analogues for Space Exploration), we selected representative anoxic analogue environments (permafrost, salt-mine, acidic lake and river, sulfur springs) for the comprehensive analysis of their microbial communities. We assessed the microbiome profile of intact cells by propidium monoazide-based amplicon and shotgun metagenome sequencing, supplemented with an extensive cultivation effort. Results: The information retrieved from microbiome analyses on the intact microbial community thriving in the MASE sites, together with the isolation of 31 model microorganisms and successful binning of 15 high-quality genomes allowed us to observe principle pathways, which pinpoint specific microbial functions in the MASE sites compared to moderate environments. The microorganisms were characterized by an impressive machinery to withstand physical and chemical pressures. All levels of our analyses revealed the strong and omnipresent dependency of the microbial communities on complex organic matter. Moreover, we identified an extremotolerant cosmopolitan group of 34 poly-extremophiles thriving in all sites. Conclusions: Our results reveal the presence of a core microbiome and microbial taxonomic similarities between saline and acidic anoxic environments. Our work further emphasizes the importance of the environmental, terrestrial parameters for the functionality of a microbial community, but also reveals a high proportion of living microorganisms in extreme environments with a high adaptation potential within habitability borders

Physiological features of Halomonas lionensis sp. nov., a novel bacterium isolated from a Mediterranean Sea sediment

A novel halophilic bacterium, strain RHS90T, was isolated from marine sediments from the Gulf of Lions, in the Mediterranean Sea. Its metabolic and physiological characteristics were examined under various cultural conditions, including exposure to stressful ones (oligotrophy, high pressure and high concentrations of metals). Based on phylogenetic analysis of the 16S rRNA gene, the strain was found to belong to the genus Halomonas in the class Gammaproteobacteria. Its closest relatives are H. axialensis and H. meridiana (98% similarity). DNA-DNA hybridizations indicated that the novel isolate is genotypically distinct from these species. The DNA G+C content of the strain is 54.4 mol%. The main fatty acids (C18:1ω7c, 2-OH iso-C15:0, C16:0 and/or C19:0 cyclo ω8c), main polar lipids (diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unidentified phosphoglycolipid) and major respiratory quinone (ubiquinone Q9) were determined. The novel isolate is heterotrophic, mesophilic, euryhaline (growth optimum ranging from 2-8% w/v NaCl) and able to grow under stressful conditions. The strain accumulates poly-β-hydroxyalkanoates granules and compatible solutes. Based on genotypic, chemotaxonomic and phenotypic distinctiveness, this isolate is likely to represent a novel species, for which the name Halomonas lionensis is proposed. The type strain of Halomonas lionensis is RHS90T (DSM 25632T = CIP 110370T = UBOCC 3186T)

Potential for fossilization of an extremotolerant bacterium isolated from a past mars analog environment

In the context of astrobiological missions to Mars, the key question is what biosignatures to search for and how? lndigenous Martian organisms, if they existed or still exist, can be classified as extremophile per se. Following this precept the FP7-funded European MASE project (Mars Analogues for Space Exploration} is investigating various aspects of anaerobic life under Mars' extreme envrionmental conditions, including the potential for preservation over long geological time periods of certain strains. In this contribution, we report on the mineralisation and preservation of Yersinia sp. in silica and gypsum, two minerals that have been reported on Mars, in cold and anaerobic conditions, similar to Martian conditions. The organism, polyextremotolerant bacterium Yersinia sp. MASE-LG-1 (hereafter named Yersinia. sp.) was isolated from the lcelandic Graenavatn Lake, an acidic (pH3), cold and oligotrophic volcanic crater lake. These organisms have a strong tolerance to diverse Mars-like stresses (Rettberg et al., 2015). We also studied the effect of physiological status on mineralisation by exposing Yersinia to two common stresses thought to have increased du ring Mars history, desiccation and radiation. The mineralisation process has been studied using microbiological (microbial viability), morphological (scanning and transmission electron microscopy), biochemical (GC-MS, Rock-Eval) and spectroscopic (FTIR and RAMAN spectroscopy) methodologies. Based on these approaches, the potential of mineralised Yersinia sp. cells to be preserved over geological time scales is also discussed. Salient results include the fact that fossilisation in gypsum solutions is slower than in silica; not all cells were mineralised, even after 6-months in the fossilising solutions, although the FTIR, Raman and SOLID biomarker signatures were lost by this time period; Rock-Eval analysis suggests that the kerogen in the fossilised strain may not survive preservation over long geological periods, although carbon molecules preserved in fossil microbial traces up to ~3.45 Ga have been detected in the rock record

Metabolie response of Yersinia MASE-LGl to osmotic stress and ionizing radiation

The MASE (Mars Analogues for space exploration) project intends to gain deeper insights into the habitability of Mars by searching for anaerobic extremophiles in Mars analogue environments on Earth like the cold sulfidic springs in Germany, the deep-subsurface salt mine in UK, the iron-rich Rio Tinto and the cold acidic lake Graenavatn in lceland. From the latter, the MASE team isolated a Yersinia sp. strain. The surface of Mars is known to host deposits of magnesium and iron sulfates, suggesting that liquid water on that planet might contain high concentrations of sulfates. Halites have also been identified. Therefore, of significance to astrobiology and understanding the habitability of Mars is to understand the microbial response to sulfate and chloride salt exposure in combination with the ubiquitous ionizing radiation in the near-surface of Mars

Methionine supplementation for multi-organ dysfunction in MetRS-related pulmonary alveolar proteinosis

International audienceIntroduction Pulmonary alveolar proteinosis related to mutations in the methionine tRNA synthetase ( MARS1 ) gene is a severe, early-onset disease that results in death before the age of 2 years in one-third of patients. It is associated with a liver disease, growth failure and systemic inflammation. As methionine supplementation in yeast models restored normal enzymatic activity of the synthetase, we studied the tolerance, safety and efficacy of daily oral methionine supplementation in patients with severe and early disease. Methods Four patients received methionine supplementation and were followed for respiratory, hepatic, growth, and inflammation-related outcomes. Their course was compared to those of historical controls. Reactive oxygen species (ROS) production by patient monocytes before and after methionine supplementation was also studied. Results Methionine supplementation was associated with respiratory improvement, clearance of the extracellular lipoproteinaceous material, and discontinuation of whole-lung lavage in all patients. The three patients who required oxygen or non-invasive ventilation could be weaned off within 60 days. Liver dysfunction, inflammation, and growth delay also improved or resolved. At a cellular level, methionine supplementation normalised the production of reactive oxygen species by peripheral monocytes. Conclusion Methionine supplementation was associated with important improvements in children with pulmonary alveolar proteinosis related to mutations in the MARS1 gene. This study paves the way for similar strategies for other tRNA synthetase deficiencies