Methanogenesis at high temperature, high ionic strength and low pH in the volcanic area of Dallol, Ethiopia

The Dallol geothermal area originated as a result of seismic activity and the presence of a shallow underground volcano, both due to the divergence of two tectonic plates. In its ascent, hot water dissolves and drags away the subsurface salts. The temperature of the water that comes out of the chimneys is higher than 100C, with a pH close to zero and high mineral concentration. These factors make Dallol a polyextreme environment. So far, nanohaloarchaeas, present in the salts that form the walls of the chimneys, have been the only living beings reported in this extreme environment. Through the use of complementary techniques: culture in microcosms, methane stable isotope signature and hybridization with specific probes, the methanogenic activity in the Dallol area has been assessed. Methane production in microcosms, positive hybridization with the Methanosarcinales probe and the δC-values measured, show the existence of extensive methanogenic activity in the hydrogeothermic Dallol system. A methylotrophic pathway, carried out by Methanohalobium and Methanosarcina-like genera, could be the dominant pathway for methane production in this environment.Agencia Estatal de Investigación (AEI), grant MDM-2017-0737 (Unidad de Excelencia “María de Maeztu”-Centro de Astrobiología INTA-CSIC) and the Spanish Ministerio de Ciencia e Innovación (MICINN

Bacterial diversity of autotrophic enriched cultures from remote, glacial Antarctic, Alpine and Andean aerosol, snow and soil samples

International audienceFour different communities and one culture of autotrophic microbial assemblages were obtained by incubation of samples collected from high elevation snow in the Alps (Mt. Blanc area) and the Andes (Nevado Illimani summit, Bolivia), from Antarctic aerosol (French station Dumont d'Urville) and a maritime Antarctic soil (King George Island, South Shetlands, Uruguay Station Artigas), in a minimal mineral (oligotrophic) media. Molecular analysis of more than 200 16S rRNA gene sequences showed that all cultured cells belong to the Bacteria domain. Phylogenetic comparison with the currently available rDNA database allowed sequences belonging to Proteobacteria (Alpha-, Betaand Gamma-proteobacteria) , Actinobacteria and Bacteroidetes phyla to be identified. The Andes snow culture was the richest in bacterial diversity (eight microorganisms identified) and the marine Antarctic soil the poorest (only one). Snow samples from Col du Midi (Alps) and the Andes shared the highest number of identified microorganisms (Agrobacterium, Limnobacter, Aquiflexus and two uncultured Alphaproteobacteria clones). These two sampling sites also shared four sequences with the Antarctic aerosol sample (Limnobacter, Pseudonocardia and an uncultured Alphaproteobacteria clone). The only microorganism identified in the Antarctica soil (Brevundimonas sp.) was also detected in the Antarctic aerosol. Most of the identified microorganisms had been detected previously in cold environments, marine sediments soils and rocks. Air current dispersal is the best model to explain the presence of very specific microorganisms, like those identified in this work, in environments very distant and very different from each other

Distribution and seasonal variability in the benthic eukaryotic community of Río Tinto (SW, Spain), an acidic, high metal extreme environment

Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Systematic and Applied Microbiology 30 (2007): 531-546, doi:10.1016/j.syapm.2007.05.003.The eukaryotic community of Río Tinto (SW, Spain) was surveyed fall, winter, and spring through the combined use of traditional microscopy and molecular approaches including Denaturing Gradient Gel Electrophoresis (DGGE) and sequence analysis of 18S rRNA gene fragments. We compared eukaryotic assemblages of surface sediment biofilms collected in January, May and September 2002 from 13 sampling stations along the river. Physicochemical data revealed extremely acidic conditions (pH ranged from 0.9 to 2.5) with high concentrations of heavy metals including up to 20 g l-1 Fe, 317 mg l-1 Zn, 47 mg l-1 As, 42 mg l-1 Cd, and 4 mg l-1 Ni. In total, 20 taxa were identified, including members of the Bacillariophyta, Chlorophyta, and Euglenophyta phyla as well as ciliates, cercomonads, amoebae, stramenopiles, fungi, heliozoan and rotifers. In general, total cell abundances were highest in fall and spring decreasing drastically in winter and the sampling stations with the most extreme conditions showed the lowest number of cells as well as the lowest diversity. Species diversity does not vary much during the year. Only the filamentous algae showed a dramatic seasonal change almost disappearing in winter and reaching the highest biomass during the summer. PCA showed a high inverse correlation between pH and most of the heavy metals analyzed as well as Dunaliella sp., while Chlamydomonas sp. is directly related to pH during May and September. Three heavy metals (Zn, Cu and Ni) remained separate from the rest and showed an inverse correlation with most of the species analyzed except for Dunaliella sp.A.A was supported by the Spanish Ministry of Education and Science through the Ramón y Cajal program. This work has been supported by grant CGL2005-05470/BOS and grants to the Centro de Astrobiología at the Instituto National de Técnica Aeroespacial

Mineralogical In-situ Investigation of Acid-Sulfate Samples from the Rio Tinto River, Spain, with a Portable XRD/XRF Instrument

A field campaign was organized in September 2006 by Centro de Astobiologica (Spain) and Washington University (St Louis, USA) for the geological study of the Rio Tinto river bed sediments using a suite of in-situ instruments comprising an ASD reflectance spectrometer, an emission spectrometer, panoramic and close-up color imaging cameras, a life detection system and NASA's CheMin 4 XRD/XRF prototype. The primary objectives of the field campaign were to study the geology of the site and test the potential of the instrument suite in an astrobiological investigation context for future Mars surface robotic missions. The results of the overall campaign will be presented elsewhere. This paper focuses on the results of the XRD/XRF instrument deployment. The specific objectives of the CheMin 4 prototype in Rio Tinto were to 1) characterize the mineralogy of efflorescent salts in their native environments; 2) analyze the mineralogy of salts and oxides from the modern environment to terraces formed earlier as part of the Rio Tinto evaporative system; and 3) map the transition from hematite-dominated terraces to the mixed goethite/salt-bearing terraces where biosignatures are best preserved

Editorial: Archaea in the Environment: Views on Archaeal Distribution, Activity, and Biogeography

On the occasion of the 10-year anniversary of Frontiers in Microbiology, this Research Topic was launched to highlight the linkages between extreme and archaeal microbiology (Teske, 2020). Archaea adapt to the physical and chemical characteristics of their habitat—such as organic matter availability, electron donor redox status, salinity, temperature, and pH—in terms of metabolic activity, community composition, gene expression patterns, and evolutionary diversification (Baker et al., 2020). Here, cultivation- and genome-based studies highlight linkages between archaea and their habitats (Figure 1)

Mars Sulfate Formation Sourced in Sulfide-Enriched Subsurface Fluids: The Rio Tinto Model

The extensive evidence for sulfate deposits on Mars provided by analyses of MER and Mars Express data shows that the sulfur played an essential role in the geochemical cycles of the planet, including reservoirs in the atmosphere, hydro-sphere and geosphere. Overall the data are consistent with a fluvial/lacustrine-evaporative origin of at least some of the sulfate deposits, with mineral precipitation through oversaturation of salty acidic fluids enriched in sulfates. This scenario requires reservoirs of sulfur and associated cations, as well as an acidic and oxidizing hydrochemistry which could be provided by surface and subsurface catching of meteoric waters resulting in the presence of sulfur-bearing gases and steam photochemistry. In this work we suggest a new scenario for the extensive generation of sulfates in Mars based on the observation of seasonal changes in the redox and pH of subsurface waters enriched in sulfur that supply the acidic Mars process analog of Rio Tinto. This model considers the long-term subsurface storage of sulfur during most of Noachian and its release from the late Noachian to Hesperian time through weathering by meteoric fluids that would acidify and oxidize the sulfur bearing compounds stored in the subsurface

Ecological successions throughout the desiccation of Tirez lagoon (Spain) as an astrobiological time-analog for wet-to-dry transitions on Mars

Tirez was a small and seasonal endorheic athalassohaline lagoon that was located in central Spain. In recent years, the lagoon has totally dried out, offering for the first time the opportunity to analyze its desiccation process as a “time-analog” to similar events occurred in paleolakes with varying salinity during the wet-to-dry transition on early Mars. On the martian cratered highlands, an early period of water ponding within enclosed basins evolved to a complete desiccation of the lakes, leading to deposition of evaporitic sequences during the Noachian and into the Late Hesperian. As Tirez also underwent a process of desiccation, here we describe (i) the microbial ecology of Tirez when the lagoon was still active 20 years ago, with prokaryotes adapted to extreme saline conditions; (ii) the composition of the microbial community in the dried lake sediments today, in many case groups that thrive in sediments of extreme environments; and (iii) the molecular and isotopic analysis of the lipid biomarkers that can be recovered from the sediments today. We discuss the implications of these results to better understanding the ecology of possible Martian microbial communities during the wet-to-dry transition at the end of the Hesperian, and how they may inform about research strategies to search for possible biomarkers in Mars after all the water was los

Preservation of underground microbial diversity in ancient subsurface deposits (>6 ma) of the rio tinto basement

The drilling of the Rio Tinto basement has provided evidence of an underground microbial community primarily sustained by the Fe and S metabolism through the biooxidation of pyrite orebodies. Although the gossan is the microbial activity product, which dates back to the Oligocene (25 Ma), no molecular evidence of such activity in the past has been reported yet. A Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) molecular analysis of a subsurface sample in the Pe\uf1a de Hierro basement has provided novel data of the ancient underground microbial community. It shows that the microbial remains are preserved in a mineral matrix composed of laminated Fe-oxysulfates and K-and Na-bearing sulfates alternating with secondary silica. In such a mineral substrate, the biomolecule traces are found in five different microstructure associations, (1) <15 micron-sized nodular microstructures composed of POn(2≤n≤4)−, (2) <30 micron-size mi-cronodules containing fatty acids, acylglycerides, and alkanol chains, (3) <20 micro-sized nodules containing NOn −(2≤n≤3) ions, (4) 40-micron size nodules with NH4+ and traces of peptides, and (5) >200-micron thick layer with N-bearing adducts, and sphingolipid and/or peptide traces. It suggests the mineralization of at least five microbial preserved entities with different metabolic ca-pabilities, including: (1) Acidiphilium/Tessaracoccus-like phosphate mineralizers, (2) microbial patches preserving phosphate-free acylglycerides bacteria, (3) nitrogen oxidizing bacteria (e.g., Acidovorax sp.), (4) traces of heterotrophic ammonifying bacteria, and (5) sphingolipid bearing bacteria (e.g., Sphin-gomonadales, and δ-Proteobacteria) and/or mineralized biofilms. The primary biooxidation process acted as a preservation mechanism to release the inorganic ions that ultimately mineralized the microbial structures

Characterization of a Subsurface Biosphere in a Massive Sulfide Deposit At Rio Tinto, Spain: Implications For Extant Life On Mars

The recent discovery of abundant sulfate minerals, particularly Jarosite by the Opportunity Rover at Sinus Merdiani on Mars has been interpreted as evidence for an acidic lake or sea on ancient Mars [1,2], since the mineral Jarosite is soluble in liquid water at pH above 4. The most likely mechanism to produce sufficient protons to acidify a large body of liquid water is near surface oxidation of pyrite rich deposits [3]. The acidic waters of the Rio Tinto, and the associated deposits of Hematite, Goethite, and Jarosite have been recognized as an important chemical analog to the Sinus Merdiani site on Mars [4]. The Rio Tinto is a river in southern Spain that flows 100 km from its source in the Iberian pyrite belt, one of the Earth's largest Volcanically Hosted Massive Sulfide (VHMS) provinces, into the Atlantic ocean. The river originates in artesian springs emanating from ground water that is acidified by the interaction with subsurface pyrite ore deposits. The Mars Analog Rio Tinto Experiment (MARTE) has been investigating the hypothesis that a subsurface biosphere exists at Rio Tinto living within the VHMS deposit living on chemical energy derived from sulfur and iron minerals. Reduced iron and sulfur might provide electron donors for microbial metabolism while in situ oxidized iron or oxidants entrained in recharge water might provide electron acceptors

The molecular record of metabolic activity in the subsurface of the Río Tinto Mars analog

In the subsurface, the interplay between microbial communities and the surrounding mineral substrate, potentially used as an energy source, results in different mineralized structures. The molecular composition of such structures can record and preserve information about the metabolic pathways that have produced them. To characterize the molecular composition of the subsurface biosphere, we have analyzed some core samples by time-of-flight secondary ion mass spectrometry (ToF-SIMS) that were collected in the borehole BH8 during the operations of the Mars Analog and Technology Experiment (MARTE) project. The molecular analysis at a micron-scale mapped the occurrence of several inorganic complexes bearing PO3-, SOx(2to4)-, NOx(2,3)-, FeOx(1,2)- SiO2-, and Cl-. Their distribution correlates with organic molecules that were tentatively assigned to saturated and monounsaturated fatty acids, polyunsaturated fatty acids, saccharides, phospholipids, sphingolipids, and potential peptide fragments. SOx- appear to be mineralizing some microstructures larger than 25 microns, which have branched morphologies, and that source SO3-bearing adducts. PO3-rich compounds occur in two different groups of microstructures which size, morphology, and composition are different. While a group of >40-micron sized circular micronodules lacks organic compounds, an ovoidal microstructure is associated with m/z of other lipids. The NO2-/NO3- and Cl- ions occur as small microstructure clusters (<20 microns), but their distribution is dissimilar to the mineralized microstructures bearing PO3-, and SO3-. However, they have a higher density in areas with more significant enrichment in iron oxides that are traced by different Fe-bearing anions like FeO2-. The distribution of the organic and inorganic negative ions, which we suggest, resulted from the preservation of at least three microbial consortia (PO4-, and NO2-/NO3-mineralizers PO4-lipid bearing microstructures), would have resulted from different metabolic and preservation pathway