Mineralization and Preservation of an extremotolerant Bacterium Isolated from an Early Mars Analog Environment

Abstract

The artificial mineralization of a polyresistant bacterial strain isolated from an acidic, oligotrophic lake was carried out to better understand microbial (i) early mineralization and (ii) potential for further fossilisation. Mineralization was conducted in mineral matrixes commonly found on Mars and Early-Earth, silica and gypsum, for 6 months. Samples were analyzed using microbiological (survival rates), morphological (electron microscopy), biochemical (GC-MS, Microarray immunoassay, Rock-Eval) and spectroscopic (EDX, FTIR, RAMAN spectroscopy) methods. We also investigated the impact of physiological status on mineralization and long-term fossilisation by exposing cells or not to Mars-related stresses (desiccation and radiation). Bacterial populations remained viable after 6 months although the kinetics of mineralization and cell-mineral interactions depended on the nature of minerals. Detection of biosignatures strongly depended on analytical methods, successful with FTIR and EDX but not with RAMAN and immunoassays. Neither influence of stress exposure, nor qualitative and quantitative changes of detected molecules were observed as a function of mineralization time and matrix. Rock-Eval analysis suggests that potential for preservation on geological times may be possible only with moderate diagenetic and metamorphic conditions. The implications of our results for microfossil preservation in the geological record of Earth as well as on Mars are discussed.

Cryogenic silicification of microorganisms in hydrothermal fluids

“…Consistent with previous works 47 , the spectral detection of non-pigmented biomass in geological substrates remains challenging. The most prominent biomolecular features in the vis-SWIR and Raman spectra are photosynthetic pigments (Fig.…”

Desiccation of the Extreme Thermoacidophile Metallosphaera sedula Grown on Terrestrial and Extraterrestrial Materials

“…Cell surface biomineralization can serve as a powerful microbial fingerprint and potential biosignature for the presence and/or activity of metal-transforming microorganisms. Assigning biogenicity to a certain structure or signature in ancient rocks remains very challenging due to probable degradation of microbial remains during diagenesis or microbial-like morphologies being produced abiotically (Gaboyer et al, 2017). The heavily encrusted desiccated cells depicted in our study may serve as relevant biosignatures to be looked for in the geological record, if they are not destroyed during diagenetic or metamorphic processes and are intact during different stages of fossilization.…”

“…To extend the search of preserved biomarkers from Earth to Mars, the polyextremotolerant bacterium Yersinia intermedia was artificially encrusted by silica and gypsum under cold and anoxic settings, similar to current Martian conditions. Yersinia cells interacted immediately with the metal-bearing materials, which favors the preservation of cells during aging due to early entombment in a metal-bearing matrix (Gaboyer et al, 2017). The capacity of biosorption depending on a specific cell wall structure has been examined in two halophilic archaeal strains of Halobacterium noricense, which sequesters uranium in cell agglomerates and structures (Bader et al, 2017).…”

The UK Centre for Astrobiology: A Virtual Astrobiology Centre. Accomplishments and Lessons Learned, 2011–2016

“…The objective of MASE was originally to isolate novel anaerobic microorganisms from a diversity of Mars analog sites and achieve their deposition within a culture collection (DSMZ) so that they can be used by other scientists. Subsequently, the project has used these organisms to undertake fundamental studies on their responses to Mars-relevant extremes and their potential for preservation during fossilization ( e.g., Beblo-Vranesevic et al, 2017; Cockell et al, 2017 ; Gaboyer et al, 2017 ). The project has also set about to test spacecraft instruments on these preserved organisms to better determine the limits of the detection of life.…”