Exploring Deep-Sea Brines as Potential Terrestrial Analogues of Oceans in the Icy Moons of the Outer Solar System.

Several icy moons of the outer solar system have been receiving considerable attention and are currently seen as major targets for astrobiological research and the search for life beyond our planet. Despite the limited amount of data on the oceans of these moon, we expect them to be composed of brines with variable chemistry, some degree of hydrothermal input, and be under high pressure conditions. The combination of these different conditions significantly limits the number of extreme locations, which can be used as terrestrial analogues. Here we propose the use of deep-sea brines as potential terrestrial analogues to the oceans in the outer solar system. We provide an overview of what is currently known about the conditions on the icy moons of the outer solar system and their oceans as well as on deep-sea brines of the Red Sea and the Mediterranean and their microbiology. We also identify several threads of future research, which would be particularly useful in the context of future exploration of these extra-terrestrial oceans

Draft Genome Sequence of Clostridium sp. Strain E02, Isolated from an Estuarine Environment

Here, we report the draft genome sequence of a strain of Clostridium isolated from sediment collected from an estuarine environment. The strain was isolated using a minimal medium designed to select for chemoautotrophic microorganisms. The strain may represent a novel species within the genus Clostridium, and this genome sequence enables further investigation into the genetic and metabolic diversity of this organism

Carbon fixation by marine ultra-small prokaryotes

Autotrophic carbon fixation is a crucial process for sustaining life on Earth. To date, six pathways, the Calvin-Benson-Bassham cycle, the reductive tricarboxylic acid cycle, the 3-hydroxypropionate bi-cycle, the Wood-Ljungdahl pathway, the dicarboxylate/4-hydroxybutyrate cycle, and the 4-hydroxybutyrate cycle have been described. Nanoorganisms, such as members of the Candidate Phyla Radiation (CPR) bacterial superphylum and the Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanoarchaeota, Nanohalorchaeota (DPANN) archaeal superphylum, could deeply impact carbon cycling and carbon fixation in ways that are still to be determined. CPR and DPANN are ubiquitous in the environment but understudied; their gene contents are not exhaustively described, and their metabolisms are not yet fully understood. Here, the completeness of each of the above pathways were quantified and tested for the presence of all key enzymes in a diversity of nanoorganisms across the World Ocean. The novel marine ultra-small prokaryotes was demonstrated to collectively harbor the genes required for carbon fixation, in particular the ‘energetically efficient’ DH pathway, and HBC pathways. This contrasted with the known carbon metabolic pathways associated with CPR memebers in aquifers, where they are described as degraders (Castelle 2015 et al., 2015, Castelle et al., 2018, Anantharaman et al., 2016). Our findings offer the possibility that nanoorganisms have a broader contribution to carbon fixation and cycling than currently assumed. Furthermore, CPR and DPANN are possibly not the only nanosized prokaryotes; therefore, the discovery of new autotrophic marine nanoorganisms, by future single cell genomics is anticipated

The Microbial Community of a Terrestrial Anoxic Inter-Tidal Zone: A Model for Laboratory-Based Studies of Potentially Habitable Ancient Lacustrine Systems on Mars

Evidence indicates that Gale crater on Mars harboured a fluvio-lacustrine environment that was subjected to physio-chemical variations such as changes in redox conditions and evaporation with salinity changes, over time. Microbial communities from terrestrial environmental analogues sites are important for studying such potential habitability environments on early Mars, especially in laboratory-based simulation experiments. Traditionally, such studies have predominantly focused on microorganisms from extreme terrestrial environments. These are applicable to a range of Martian environments; however, they lack relevance to the lacustrine systems. In this study, we characterise an anoxic inter-tidal zone as a terrestrial analogue for the Gale crater lake system according to its chemical and physical properties, and its microbiological community. The sub-surface inter-tidal environment of the River Dee estuary, United Kingdom (53°21'015.40" N, 3°10'024.95" W) was selected and compared with available data from Early Hesperian-time Gale crater, and temperature, redox, and pH were similar. Compared to subsurface ‘groundwater’-type fluids invoked for the Gale subsurface, salinity was higher at the River Dee site, which are more comparable to increases in salinity that likely occurred as the Gale crater lake evolved. Similarities in clay abundance indicated similar access to, specifically, the bio-essential elements Mg, Fe and K. The River Dee microbial community consisted of taxa that were known to have members that could utilise chemolithoautotrophic and chemoorganoheterotrophic metabolism and such a mixed metabolic capability would potentially have been feasible on Mars. Microorganisms isolated from the site were able to grow under environment conditions that, based on mineralogical data, were similar to that of the Gale crater’s aqueous environment at Yellowknife Bay. Thus, the results from this study suggest that the microbial community from an anoxic inter-tidal zone is a plausible terrestrial analogue for studying habitability of fluvio-lacustrine systems on early Mars, using laboratory-based simulation experiments

A Study of the Microbial Community at the Interface between Granite Bedrock and Soil Using a Culture-Independent and Culture-Dependent Approach

The dissolution of minerals plays an important role in the formation of soils and sediments. In nutrient limiting soils, minerals constitute a major reservoir of bio-essential cations. Of particular interest is granite as it is the major rock type of the continental land mass. Although certain bacteria have been shown to enhance weathering of granite-forming minerals, little is known about the dissolution of granite, at the whole rock scale, and the microbial community involved. In this study, both culture-independent and culture-dependent approaches were used to study the bacterial community at the interface between granite bedrock and nutrient limiting soil in Dartmoor National Park, United Kingdom. High throughput sequencing demonstrated that over 70% of the bacterial population consisted of the bacterial classes Bacilli, Beta-proteobacteria and Gamma-proteobacteria. Bacteria belonging to the genera Serratia, Pseudomonas, Bacillus, Paenibacillus, Chromobacterium and Burkholderia were isolated from the sample site. All of the isolates were able to grow in a minimal growth medium, which contained glucose and ammonium chloride, with granite as the sole source of bio-essential elements. Sixty six percent of the isolates significantly enhanced basalt dissolution (p < 0.05). Dissolution of Si, K, Ca and Mg correlated with production of oxalic acid and acidification. The results of this study suggest that microorganisms in nutrient limiting soils can enhance the rate of granite dissolution, which is an important part of the biogeochemical cycle

Planetary Protection in the New Space Era: Science and Governance

Committee of Space Research’s Planetary Protection Policy is a triumph of technocratic governance in the global sphere. The Policy is produced by a group of scientific experts and subsequently enjoys high regard among the scientific and space community. However, as Committee of Space Research is an independent organization without any legal mandate the Planetary Protection Policy is an example of so-called “soft law” or a non-binding international instrument, in short, no one is under any legal obligation to comply with them. The policy is linked to Article IX of the Outer Space Treaty and its provision calling for the avoidance of “harmful contamination” of the Moon and other celestial bodies .While space activities beyond Earth orbit have been the exclusive preserve of government scientific space agencies this has posed little problem. However as private and “non-science” space activities proliferate and begin to spread their reach beyond Earth orbit, the Planetary Protection Policy is being tested. This paper will examine the challenges of developing and maintaining an effective planetary protection regime in this “NewSpace” era. This will involve looking at the existing policies, as well as the governance framework they sit within. However, it is also necessary to consider and understand the scientific basis not just for the specifics of the policy itself but the necessity of it. Finally, this paper will consider whether a broader “environmental” framework is needed as space activities diversity in type and location

Viable metabolisms in a simulated martian environments

Microbes have multiple ways of producing energy. Which of these methods are possible depends on the chemistry of the environment the microbes are in (e.g. not enough of a metal or too much salt), with only specific methods working in certain environments. The same would be true of any waters that might continue to exist on Mars. To narrow down which methods of producing energy would be theoretically possible we simulated martian waters using a collection of minerals that are chemically similar to the chemistry measured by the Mars rover Curiosity in a crater on Mars. We added mud from an estuary to the simulated martian water and identified which microbes were able to grow. We then repeatedly transferred the growing microbes to fresh “martian” water to dilute out the nutrients from the mud. Over time we observed that most of the microbes from the mud have been lost but a few specific microbes were growing well. From this we hope to investigate changes in the chemistry of the water that happen because of these microbes, to try and identify specific chemistries that can be looked for by the future rover missions on Mars seeking evidence of life

Modelling Water-Rock Interactions in the Sub-surface Environment of Enceladus.

Understanding the geochemical cycles occurring at the water-rock interface on Enceladus is crucial for establishing the potential habitability of the subsurface environment. Using data collected by the Cassini spacecraft (2005-2017) and estimates of the starting composition of the sub-surface ocean on Enceladus, we have modelled how the ocean interacts with a silicate simulant representing the rocky interior. The results from these models define a hypothesized modern ocean chemistry and provide an insight into the geochemical reactions occurring at the water-rock interface. The results from this work support observations made by Cassini, suggesting our chosen starting conditions could provide an insight into the history of Enceladus

Microbial growth in simulated martian environments

In this study, four new simulants have been developed, and their associated fluid chemistries have been derived for use in a series of microbiological simulation experiments. These experiments will determine if aqueous environments on Mars, past or present, could potentially support microbial life and identify any key geochemical biosignatures that may arise as a result of that life