The comprehensive ‘MICRO-life detection platform’ applied to in situ research at Mars and Icy Moons terrestrial analogs 

Abstract

<p>Detecting unquestionable signatures of biological activity in extra-terrestrial Solar System bodies is one of the most challenging objectives in Astrobiology. Discerning if these signatures have been generated by extinct or actual extant organisms would also be of principal interest. While most of the latest exploration missions to Mars launched on 2020 (<em>i.e.</em> NASA’s Mars 2020) or being launched in the near future (ESA’s ExoMars) carry instruments - Raman spectrometers and MOMA (Mars Organic Molecule Analyser) - able to detect organic compounds, they lack the capabilities to undoubtedly confirm those signatures have been generated either by past or extant life.</p><p>Here we present the <strong>MICRO-life detection platform</strong>, a comprehensive, multi-technique instrumentation for molecular microbial ecology studies, intended to take part in future exploratory space missions. The MICRO-life detection platform already includes three complementary tools that, in the next future, would be operated at once without any human intervention. Thus, findings coming out from all the included techniques would be combined for a better assignment of putative positive results.</p><p>The first instrument included in the platform is <strong>MagLysis</strong>, a small, lightweight, solid-state, automatable instrument designed to help in the extraterrestrial detection of the most unambiguous and informative biosignatures: nucleic acids (NA). MagLysis aims to bead-beat the biomass in a sample to disrupt the cell walls and membranes, thus releasing the contents of the cell cytoplasm, including DNA and RNA molecules. The unique feature of MagLysis is that only ferromagnetic beads (made of stainless steel) are agitated inside the vessel by two opposing, low-inductance electromagnets, resulting in mechanical lysis (Fig. 1A). Reducing the mass actuated by the device to only the beads means that the power required is potentially low and that there are fewer moving parts, both extremely important features for space exploratory missions. Moreover, extracted DNA was successfully amplified by PCR and subsequently sequenced by the second instrument included in the platform, Oxford Nanopore Technologies’ (ONT) MinION.</p><p><strong>ONT MinION</strong> is a fully portable device (Fig. 1B) able to carry out real-time analysis of DNA, RNA, proteins and other smaller molecules. This instrument has been tested in the International Space Station (ISS) and in field campaigns at our lab, with results that have been already published. With it, feasible sequence data can be obtained within 48 h from natural samples with only ~ 0.001 ng of DNA, as it has been already tested by us on terrestrial analogues of Mars and the Icy Moons, such as the High Arctic, Antarctica and Utah and Atacama Desert samples, as well as on samples that have been subjected to long periods of Mars-like conditions. Additionally, MinION results have been proved to reflect very similar microbial community compositions to those obtained by other techniques, such as Illumina MiSeq sequencing or LDChip.</p><p>Complementary to MinION, MICRO-life detection platform also includes a method for the detection and characterization of viable microorganisms based on their metabolic capacities: Microfluidic microbial activity microassay (μMAMA). <strong>μMAMA</strong> is a multi-well plate that focus on the capability of extant microorganisms - including yet unculturable species - to become metabolically active when they are supplied with different organic and inorganic substrates. The technique itself is based on redox-indicator dyes chemically associated to the substrates than can subsequently be measured by a spectrophotometer (Fig. 1C); additionally, it has been proved to work in a wide range of pH values or temperatures. This has been the case of samples from the High Arctic, where this technique has already shown that metabolically active communities were differentially found at 5 °C or 20 °C. Subsequently, those communities yielded positive results in a MinION sequencing process, showing that most of the members in the active communities belonged to <em>Pseudomonas</em> genus and demonstrating the complementarity of both techniques.</p><p>Attending to the results already obtained from cold extreme environments in polar regions and deserts (Mars and Icy Moons analogs), MICRO-life detection platform and self-developed techniques within are very promising tools for Astrobiological research. Their ease-of-use and the proof of being resistant to the most extreme conditions including space travel ones, make the platform a strong candidate to be employed in future extreme environment research and, in the mid-term, included in space exploratory missions as an important element to the search for extant extra-terrestrial life.<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.5e221b47b48263484682561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=b3d51c20541716076e1c98e93067a399&ct=x&pn=gepj.elif&d=1" alt=""></p>