NLSI Lunar Science Conference (2008)
BIOGEOCHEMICAL ACTIVITY OF CYANOBACTERIA: IMPLICATIONS FOR OUTPOST LUNAR MISSIONS. I. I. Brown1, J. A. Jones1, S. A. Sarkisova1, D. H. Garrison1, C.C. Allen1, G.Sanders1, D. S. McKay1 1 NASA JSC (Mail code: ARES-KA, 2101 NASA Road One, Houston, TX, 77058; igor.i.brown.@nasa.gov; email@example.com Introduction: A major goal for the Vision of Space Exploration is to extend human presence across the solar system. With current technology, however, all required consumables for these missions (propellant, air, food, water) as well as habitable volume and shielding to support human explorers will need to be brought from Earth. In-situ production of consumables (In-Situ Resource Utilization-ISRU) will significantly facilitate current plans for human exploration and colonization of the solar system, especially by reducing the logistical overhead such as recurring launch mass. The most challenging technology developments for future lunar settlements may lie in the extraction of elements (O, Fe, Mn, Ti, Si, etc) from local rocks and soils for life support, industrial feedstock and the production of propellants. With few exceptions , nearly all technology development to date has employed an approach based on inorganic chemistry . None of these technologies include concepts for integrating the ISRU system with a bioregenerative life support system and a food production system. The European Micro-Ecological Life Support System Alternative (MELiSSA) is an advanced concept for organizing a bioregenerative system for long term space flights and extraterrestrial settlements . The central point of MELiSSA is the cultivation of cyanobacteria (CB). However, the MELiSSA system is a net consumer of ISRU products without a net return to in-situ technologies, e.g. to extract elements, as a result of complete closure of MELiSSA. On the other hand, the physical-chemical processes for ISRU are typically massive (relative to the rate of oxygen production), require significant power (tens of kWh/kg), and in many processes requires high temperatures (~1000oC) to be effective; therefore they are not compatible with closed life support systems such as MELiSSA. Contemporary CB began to occupy different ecological niches of Precambrian Earth about 3 billion years ago when geochemical parameters of both Earth and Moon were closer than today. Some cyanobacteria, e.g. Spirulina, demonstrate significant resistance to γ radiation . Other cyanobacteria have been shown to survive the desiccating, freezing conditions of space in orbital experiments . CB are also known as very effective litholyts . Given this trait, disintegration of rocks by extracellular products of microbes (bioweathering), seems to be applicable to ISRU needs on the Moon. Using organic acids, bacteria are able to dissolve different rocks, including such hard rocks as volcanic glass , granites, hornblende, and basalts . Bioweathering of lunar regolith for Moon exploration has been considered by studies on the preparation of lunar-derived soil . Because the Moon is practically free of organic compounds but is rich in inorganic elements, it makes sense to use autotrophic cyanobacteria for future extraterrestrial biotechnologies . Recent workshop on “Cyanobacteria in a lunar environment” (Ames Research Center, January, 2008) has confirmed the rationality and possibility of the application of CB for outpost lunar missions. Here we report about the progress of our studies on the biogeochemical activities of litholytic CB, which might be useful for ISRU and/or life support needs. Results: We have used several species of siderophilic CB isolated from iron-depositing hot springs in Yellowstone National Park  to characterize their bioweathering activity. Severe reduction of iron and trace elements in incubation media led to the depression of CB growth while the presence of any analog of either lunar or martian soil in culture media stimulated the growth of CB. In parallel, it was found that rocks stimulated the production of 2-ketoglutaric acid by several species of siderophilic CB. This result led to the hypothesis that the bioweathering activity of CB is bound to the secretion of natural chelators as organic acids. It was also found that the cultivation of CB with ilmenite affects the rate of O2 evolution by CB and the character of the effect is species dependent. Further studies showed that the efficiency of different cyanobacterial species to break down minerals in lunar simulants varied considerably depending on the species. The selection of the most efficient “biominers” within our collection of siderophilic cyanobacteria was carried out. In particular, the cyanobacterial isolate JSC-12 (previously unidentified species) demonstrated the highest bioweathering activity in comparison to the other isolates. We also carried out stepped selection of the population of endogenous mutants of JSC-12 isolate with elevated resistance to dissolved iron and titanium. As a result, filaments of JSC-12 culture were able to grow di-
NLSI Lunar Science Conference (2008)
rectly on the surface of mineral particles enriched with different trace metals (figure 1).
Fig. 1. SEM view of two particles of lunar soil simulant (NU-LHT-IM Pilot).
Top: a particle of Pilot simulant submerged 4 weeks in a sterile medium; bottom: a particle of same after 4 weeks incubation in the same medium now containing cyanobacteria (strain JSC-12).
aqueous phase where they will available for different applications, such as the preparation of substrates for hydroponic cultivation. The level of our knowledge about the interaction of CB with extraterrestrial minerals is rapidly increasing, but is currently at a low technology readiness level. As a result of pilot studies, we are developing a concept for semi-closed integrated system that uses a bioreactor containing CB for extracting useful elements from the regolith. This bioreactor powered by sunlight can revitalize air by utilization of CO2 and production of O2. Some components of cyanobacterial biomass can be used directly as nutritional supplements . Such a system could be the foundation of a self-sustaining extraterrestrial outpost . A potential advantage of a cyanobacterial photoreactor placed between LSS and ISRU loops is the possibility of supplying these systems with extracted elements and compounds from the regolith. In addition, waste regolith and CB biomass can be used for organic and inorganic enrichment of artificial soil for the cultivation of high plants. The most critical conclusion is that a semi-closed life support system tied to an ISRU biofacility might be more efficient for support of an extraterrestrial outpost than closed environmental systems. Such a synthesis of technological capability could decrease the demand for energy, transfer mass and cost of future exploration. References:  Johansson K.R. (1992) Space resources. Washington, D.C. 20402, USA.Vol. 3, 222241.  Allen, C. C. et al. (1996) J. Geophys. Res. 101, 26085-26095.  Hendrickx, L., H. De Wever, et al. (2006) Res. in Microbiology, 157: 77-86.  Kim M.J. et al. (2000) Radiation Physics, 57, 55-58.  Mancinelli R.L. et al. (1998) Adv. Space Res., 22, 327–334.  Rios de los A., Wierzchos J., Sancho L.G., Ascaso C. (2003) Environ. Microbiol., 4, 2317.  Fisk M.R. et al., (2006) Astrobiology. 6, 48-68.  Kalinowski, B.E., (2000) Chemical Geology. 169, 357-370.  Helmke P.A. and Corey R.B. (1989) In: Lunar Base Agriculture. 193-212.  Brown I.I. et al. (2007) Rutgers Symposium on Lunar Settlements, 79.  Brown I.I., Allen C.C., Mummey D.L., Sarkisova S.A., McKay D.S. (2007) Algae and Cyanobacteria in Extreme Environments, 425-442.  Handford A.J. (2006) “Exploration Life Support Baseline Values and Assumptions” NASA CR-2006, Johnson Space Center.
CB filaments can be seen partially embedded in form-fitting depressions and grooves, presumably caused by partial dissolution of the mineral promoted by the cells. The model for studying the bioweathering of lunar simulants was elaborated by further experiments. Grains of either Minnesota basalt or ilmenite were imbedded in epoxy. Solidified coupons were polished and were studied by scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy. Reduction of the diameter of a Minnesota basalt grains after dissolution by a CB cells was observed. Elemental maps of iron distribution confirmed iron removal from iron-bearing mineral grains. TEM studies revealed that siderophilic CB accumulate colloidal iron in and on cyanobacterial cells while chemical analysis shows that dissolved or colloidal iron does not accumulate in the medium away from the cells. Perspectives: Preliminary results suggest that it would be reasonable to use the bioweathering potential of litholytic CB for the transition of different chemical elements from extraterrestrial rocks to an