Microbial Community for Growing Pioneer Plants in a Lunar Greenhouse

It may be assumed that the first plants in a lunar base will play a main role in forming a protosoil of acceptable fertility needed for purposively growing second generation plants like wheat, rice, tulips, etc. The residues of the first-generation plants could be composted and transformed by microorganisms into a soil-like substrate within a loop of regenerative life support system. The lunar regolith may be used as a substrate for plant growth at the very beginning of a mission to reduce its cost. The use of microbial communities for priming plants will allow to facilitate adaptation to stressful conditions and to support the plant development under growth limiting conditions. Well-defined plant-associated bacteria were used for growing three cultivars to colonize of French marigold (Tagetes patula L.) in anorthosite, a substrate of low bioavailability, analogous to a lunar rock. The consortium was composed of plant growth promoting rhizobacteria and the bacterium Paenibacillus sp. IMBG156 which stimulated seed germination, better plant development, and finally, the flowering of inoculated tagetes. In contrast, control plants grew poorly in a sterile anorthosite and practically did not survive until flowering. Analysis of bacterial community composition showed that all species colonized plant roots, however, the rate of colonization depended on the allelopatic characteristics of marigold varieties. Bacteria of consortium were able to liberate some elements (Fe, Si, Ni, Co, Cu, Zn, Cr) from substrate anorthosite. Plant colonization by mixed culture of bacterial strains resulted in increase of accumulation by the plant of potassium and cobalt and in lowering the level of toxic metal accumulation. It was assumed that rationally assembled consortium of bacterial strains promoted germination of marigold seeds and supported the plant development under growth limiting conditions by means of bioleaching plant essential nutritional elements and protecting of the plant against hyperaccumulation of some toxic metals. THE PROTOTYPE PLANT-BACTERIA MICROCOSM FOR A LUNAR BASE The ability to grow plants in space self-perpetuating gardens is topical for providing an advanced life support system for humans while inhabiting a permanently manned lunar base (PMBL). Plants could provide fresh food, oxygen, and clean water for explorers living in PMLB. A lunar garden has to supplement less appetizing packaged food brought from Earth. The ornamental plants will play role in reducing stress and in recovering emotional potency in PMLB personnel. Lunar agriculture has the potential to earn the needed export of fresh food to other space locations at a decided fiscal advantage over fresh products brought up from Earth. To reduce a cost of early missions to the Moon, it would be practical to use local materials such as a lunar regolith for growing plants in lunar greenhouses. The use of bacteria to govern a decomposition of silicate rocks, a liberation of essential growth elements for plants, and to deliver them to the plant is a key idea in precursory scenario of growing pioneer plants for a lunar base (Kozyrovska et al., 2004; 2005). The objectives of this study were to study bioleaching capacity of bacteria in batch experiments with anorthosite as a component of nutrient media, as well as in the model plant microcosms placed in plant growth chambers under controlled conditions.