Microbially-Enhanced Vanadium Mining and Bioremediation Under Micro- and Mars Gravity on the International Space Station.

As humans explore and settle in space, they will need to mine elements to support industries such as manufacturing and construction. In preparation for the establishment of permanent human settlements across the Solar System, we conducted the ESA BioRock experiment on board the International Space Station to investigate whether biological mining could be accomplished under extraterrestrial gravity conditions. We tested the hypothesis that the gravity (g) level influenced the efficacy with which biomining could be achieved from basalt, an abundant material on the Moon and Mars, by quantifying bioleaching by three different microorganisms under microgravity, simulated Mars and Earth gravitational conditions. One element of interest in mining is vanadium (V), which is added to steel to fabricate high strength, corrosion-resistant structural materials for buildings, transportation, tools and other applications. The results showed that Sphingomonas desiccabilis and Bacillus subtilis enhanced the leaching of vanadium under the three gravity conditions compared to sterile controls by 184.92 to 283.22%, respectively. Gravity did not have a significant effect on mean leaching, thus showing the potential for biomining on Solar System objects with diverse gravitational conditions. Our results demonstrate the potential to use microorganisms to conduct elemental mining and other bioindustrial processes in space locations with non-1 × g gravity. These same principles apply to extraterrestrial bioremediation and elemental recycling beyond Earth.

Space station biomining experiment demonstrates rare earth element extraction in microgravity and Mars gravity.

Microorganisms are employed to mine economically important elements from rocks, including the rare earth elements (REEs), used in electronic industries and alloy production. We carried out a mining experiment on the International Space Station to test hypotheses on the bioleaching of REEs from basaltic rock in microgravity and simulated Mars and Earth gravities using three microorganisms and a purposely designed biomining reactor. Sphingomonas desiccabilis enhanced mean leached concentrations of REEs compared to non-biological controls in all gravity conditions. No significant difference in final yields was observed between gravity conditions, showing the efficacy of the process under different gravity regimens. Bacillus subtilis exhibited a reduction in bioleaching efficacy and Cupriavidus metallidurans showed no difference compared to non-biological controls, showing the microbial specificity of the process, as on Earth. These data demonstrate the potential for space biomining and the principles of a reactor to advance human industry and mining beyond Earth.

No Effect of Microgravity and Simulated Mars Gravity on Final Bacterial Cell Concentrations on the International Space Station: Applications to Space Bioproduction.

Microorganisms perform countless tasks on Earth and they are expected to be essential for human space exploration. Despite the interest in the responses of bacteria to space conditions, the findings on the effects of microgravity have been contradictory, while the effects of Martian gravity are nearly unknown. We performed the ESA BioRock experiment on the International Space Station to study microbe-mineral interactions in microgravity, simulated Mars gravity and simulated Earth gravity, as well as in ground gravity controls, with three bacterial species: Sphingomonas desiccabilis, Bacillus subtilis, and Cupriavidus metallidurans. To our knowledge, this was the first experiment to study simulated Martian gravity on bacteria using a space platform. Here, we tested the hypothesis that different gravity regimens can influence the final cell concentrations achieved after a multi-week period in space. Despite the different sedimentation rates predicted, we found no significant differences in final cell counts and optical densities between the three gravity regimens on the ISS. This suggests that possible gravity-related effects on bacterial growth were overcome by the end of the experiment. The results indicate that microbial-supported bioproduction and life support systems can be effectively performed in space (e.g., Mars), as on Earth.

0.25 Ga Salt Deposits Preserve Signatures of Habitable Conditions and Ancient Lipids.

Polygonal features in a ∼250 million-year-old Permian evaporitic deposit were investigated for their geological and organic content to test the hypothesis that they could preserve the signature of ancient habitable conditions and biological activity. Investigations on evaporitic rock were carried out as part of the MIne Analog Research (MINAR) project at Boulby Mine, the United Kingdom. The edges of the polygons have a higher clay content and contain higher abundances of minerals such as quartz and microcline, and clays such as illite and chlorite, compared with the interior of polygons, suggesting that the edges were preferred locations for the accumulation of weathering products during their formation. The mineral content and its strontium isotope ratio suggest that the material is from continental weathering at the borders of the Permian Zechstein Sea. The edges of the polygons contain material with mean δ13C and δ15N values of -20.8 and 5.3, respectively. Lipids, including alkanes and hopanes, were extracted from the interior and edges of the polygons, which are inferred to represent organic material entrained in the evaporites when they were formed. The presence of long-chain alkanes (C20-C35) that lack a carbon preference, low abundances of C23-C29 hopanes, and lack of marine, evaporitic, or thermal maturity indicators show that lipid biomarkers were, at least in part, potentially derived from a continental source and have not undergone significant thermal maturation since deposition. Lipid extractions using weak acids revealed significantly more lipids than those without acid, potentially indicating that encapsulation was not the only type of preservation mechanism occurring in Boulby salts. These data demonstrate the potential for ancient evaporites and their polygons to preserve information on local geological conditions, ancient habitability, and evidence of life. The data show that analogous martian evaporitic deposits are good targets for future life detection missions and the investigation of ancient martian habitability.

Aggregated Cell Masses Provide Protection against Space Extremes and a Microhabitat for Hitchhiking Co-Inhabitants.

The European Space Agency's EXPOSE facility, located on the outside of the International Space Station, was used to investigate the survival of cell aggregates of a cyanobacterium, Gloeocapsa sp., in space and simulated martian conditions for 531 days in low Earth orbit as part of the "Biofilm Organisms Surfing Space" (BOSS) experiments. Postflight analysis showed that the cell aggregates of the organism conferred protection against space conditions compared to planktonic cells. These cell aggregates, which consisted of groups of metabolically inactive cells that do not form structured layered biofilms, demonstrated that disordered "primitive" aggregates of sheathed cells can provide protection against environmental stress such as UV radiation. Furthermore, the experiment demonstrated that the cyanobacterial cell aggregates provided a microhabitat for a smaller bacterial co-cultured species that also survived in space. This observation shows that viable cells can "hitchhike" through space within the confines of larger protecting cells or cell aggregates, with implications for planetary protection, human health, and other space microbiology applications.

A Low-Diversity Microbiota Inhabits Extreme Terrestrial Basaltic Terrains and Their Fumaroles: Implications for the Exploration of Mars.

A major objective in the exploration of Mars is to test the hypothesis that the planet hosted life. Even in the absence of life, the mapping of habitable and uninhabitable environments is an essential task in developing a complete understanding of the geological and aqueous history of Mars and, as a consequence, understanding what factors caused Earth to take a different trajectory of biological potential. We carried out the aseptic collection of samples and comparison of the bacterial and archaeal communities associated with basaltic fumaroles and rocks of varying weathering states in Hawai'i to test four hypotheses concerning the diversity of life in these environments. Using high-throughput sequencing, we found that all these materials are inhabited by a low-diversity biota. Multivariate analyses of bacterial community data showed a clear separation between sites that have active fumaroles and other sites that comprised relict fumaroles, unaltered, and syn-emplacement basalts. Contrary to our hypothesis that high water flow environments, such as fumaroles with active mineral leaching, would be sites of high biological diversity, alpha diversity was lower in active fumaroles compared to relict or nonfumarolic sites, potentially due to high-temperature constraints on microbial diversity in fumarolic sites. A comparison of these data with communities inhabiting unaltered and weathered basaltic rocks in Idaho suggests that bacterial taxon composition of basaltic materials varies between sites, although the archaeal communities were similar in Hawai'i and Idaho. The taxa present in both sites suggest that most of them obtain organic carbon compounds from the atmosphere and from phototrophs and that some of them, including archaeal taxa, cycle fixed nitrogen. The low diversity shows that, on Earth, extreme basaltic terrains are environments on the edge of sustaining life with implications for the biological potential of similar environments on Mars and their exploration by robots and humans.

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

The UK Centre for Astrobiology (UKCA) was set up in 2011 as a virtual center to contribute to astrobiology research, education, and outreach. After 5 years, we describe this center and its work in each of these areas. Its research has focused on studying life in extreme environments, the limits of life on Earth, and implications for habitability elsewhere. Among its research infrastructure projects, UKCA has assembled an underground astrobiology laboratory that has hosted a deep subsurface planetary analog program, and it has developed new flow-through systems to study extraterrestrial aqueous environments. UKCA has used this research backdrop to develop education programs in astrobiology, including a massive open online course in astrobiology that has attracted over 120,000 students, a teacher training program, and an initiative to take astrobiology into prisons. In this paper, we review these activities and others with a particular focus on providing lessons to others who may consider setting up an astrobiology center, institute, or science facility. We discuss experience in integrating astrobiology research into teaching and education activities. Key Words: Astrobiology-Centre-Education-Subsurface-Analog research. Astrobiology 18, 224-243.

Perchlorates on Mars enhance the bacteriocidal effects of UV light.

Perchlorates have been identified on the surface of Mars. This has prompted speculation of what their influence would be on habitability. We show that when irradiated with a simulated Martian UV flux, perchlorates become bacteriocidal. At concentrations associated with Martian surface regolith, vegetative cells of Bacillus subtilis in Martian analogue environments lost viability within minutes. Two other components of the Martian surface, iron oxides and hydrogen peroxide, act in synergy with irradiated perchlorates to cause a 10.8-fold increase in cell death when compared to cells exposed to UV radiation after 60 seconds of exposure. These data show that the combined effects of at least three components of the Martian surface, activated by surface photochemistry, render the present-day surface more uninhabitable than previously thought, and demonstrate the low probability of survival of biological contaminants released from robotic and human exploration missions.

The Janus face of iron on anoxic worlds: iron oxides are both protective and destructive to life on the early Earth and present-day Mars.

The surface of the early Earth was probably subjected to a higher flux of ultraviolet (UV) radiation than today. UV radiation is known to severely damage DNA and other key molecules of life. Using a liquid culture and a rock analogue system, we investigated the interplay of protective and deleterious effects of iron oxides under UV radiation on the viability of the model organism, Bacillus subtilis. In the presence of hydrogen peroxide, there exists a fine balance between iron oxide's protective effects against this radiation and its deleterious effects caused by Photo-Fenton reactions. The maximum damage was caused by a concentration of hematite of ∼1 mg/mL. Concentrations above this confer increasing protection by physical blockage of the UV radiation, concentrations below this cause less effective UV radiation blockage, but also a correspondingly less effective Photo-Fenton reaction, providing an overall advantage. These results show that on anoxic worlds, surface habitability under a high UV flux leaves life precariously poised between the beneficial and deleterious effects of iron oxides. These results have relevance to the Archean Earth, but also the habitability of the Martian surface, where high levels of UV radiation in combination with iron oxides and hydrogen peroxide can be found.

Liquid Water Restricts Habitability in Extreme Deserts.

Liquid water is a requirement for biochemistry, yet under some circumstances it is deleterious to life. Here, we show that liquid water reduces the upper temperature survival limit for two extremophilic photosynthetic microorganisms (Gloeocapsa and Chroococcidiopsis spp.) by greater than 40°C under hydrated conditions compared to desiccated conditions. Under hydrated conditions, thermal stress causes protein inactivation as shown by the fluorescein diacetate assay. The presence of water was also found to enhance the deleterious effects of freeze-thaw in Chroococcidiopsis sp. In the presence of water, short-wavelength UV radiation more effectively kills Gloeocapsa sp. colonies, which we hypothesize is caused by factors including the greater penetration of UV radiation into hydrated colonies compared to desiccated colonies. The data predict that deserts where maximum thermal stress or irradiation occurs in conjunction with the presence of liquid water may be less habitable to some organisms than more extreme arid deserts where organisms can dehydrate prior to being exposed to these extremes, thus minimizing thermal and radiation damage. Life in extreme deserts is poised between the deleterious effects of the presence and the lack of liquid water. Key Words: Deserts-Extremophiles-Stress-High temperatures-UV radiation-Desiccation. Astrobiology 17, 309-318.