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

The responses of an anaerobic microorganism, Yersinia intermedia MASE-LG-1 to individual and combined simulated Martian stresses

The limits of life of aerobic microorganisms are well understood, but the responses of anaerobic microorganisms to individual and combined extreme stressors are less well known. Motivated by an interest in understanding the survivability of anaerobic microorganisms under Martian conditions, we investigated the responses of a new isolate, Yersinia intermedia MASE-LG-1 to individual and combined stresses associated with the Martian surface. This organism belongs to an adaptable and persistent genus of anaerobic microorganisms found in many environments worldwide. The effects of desiccation, low pressure, ionizing radiation, varying temperature, osmotic pressure, and oxidizing chemical compounds were investigated. The strain showed a high tolerance to desiccation, with a decline of survivability by four orders of magnitude during a storage time of 85 days. Exposure to X-rays resulted in dose-dependent inactivation for exposure up to 600 Gy while applied doses above 750 Gy led to complete inactivation. The effects of the combination of desiccation and irradiation were additive and the survivability was influenced by the order in which they were imposed. Ionizing irradiation and subsequent desiccation was more deleterious than vice versa. By contrast, the presence of perchlorates was not found to significantly affect the survival of the Yersinia strain after ionizing radiation. These data show that the organism has the capacity to survive and grow in physical and chemical stresses, imposed individually or in combination that are associated with Martian environment. Eventually it lost its viability showing that many of the most adaptable anaerobic organisms on Earth would be killed on Mars today

« Obituary: Jean-Michel Berthelot », Newsletter of Research Commitee on the History of Sociology (RSCH),

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« Les voyages d'étude aux États-unis dans les années 1950 : de l'initiation à la redéfinition de la sociologie française. »,

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Mattei Dogan, pionnier de la recherche de la sociologie politique au Centre d’Études Sociologiques (1954-1968)

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Raymond Ledrut, sociologue bâtisseur, ou les frontières de la sociologie en question

International audienceLa sociologie toulousaine a une histoire ancienne, elle est présente dès la fin des années 50 en grande partie grâce à Raymond Ledrut, sociologue urbain. Nous traiterons de l’histoire de la sociologie toulousaine, de ses modalités de construction, en mettant l’accent sur deux caractéristiques : ses liens disciplinaires (notamment avec la philosophie et la géographie) et la notion de « patron » avec le rôle prépondérant de Raymond Ledrut. L’objectif est d’examiner les modalités à la fois historiques, disciplinaires et institutionnelles, mais aussi locales ou régionales de la construction de la sociologie. En effet, regarder les liens disciplinaires de la sociologie permet de comprendre l’histoire de sa filiation et de son autonomisation, avec éventuellement des nuances locales liées à l’histoire propre d’une université et pour laquelle nous verrons l’importance du rôle joué par le « patron » – en l’occurrence ici R. Ledrut pour l’Université de Toulouse.Enfin, en évoquant le parcours scientifique et institutionnel de R. Ledrut, nous interrogerons aussi les notions de frontières disciplinaires et nationales de la sociologie. En effet, R. Ledrut n’a pas seulement été un bâtisseur de la discipline en travaillant à son autonomisation, il a été aussi un fervent défenseur de la collaboration disciplinaire, tout en œuvrant, devenu président de l’AISLF en 1978, à son internationalisation

“Such a Small World”. The International Network of Francophone Sociologists in Time and Space

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