BIOLOGICAL POTENTIAL OF EXTRATERRESTRIAL MATERIALS .2. MICROBIAL AND PLANT-RESPONSES TO NUTRIENTS IN THE MURCHISON CARBONACEOUS METEORITE

Meteoritic materials are investigated as potential early planetary nut rients. Aqueous extracts of the Murchison C2 carbonaceous meteorite ar e utilized as a sole carbon source by microorganisms, as demonstrated by the genetically modified Pseudomonas fluorescence equipped with the lax gene. Nutrient effects are observed also with the soil microorgan isms Nocardia asteroides and Arthrobacter pascens that reach populatio ns up to 5 x 10(7) CPU/ml in meteorite extracts, similar to population s in terrestrial soil extracts, Plant tissue cultures of Asparagus off icinalis and Solanum tuberosum (potato) exhibit enhanced pigmentation and some enhanced growth when meteorite extracts are added to partial nutrient media, but inhibited growth when added to full nutrient solut ion. The meteorite extracts lead to large increases in S, Ca, Mg, and Fe plant tissue contents as shown by X-ray fluorescence, while P, K, a nd Cl contents show mixed effects, In both microbiological and plant t issue experiments, the nutrient and inhibitory effects appear to be be st balanced for growth at about 1:20 (extracted solid:H2O) ratios, The results suggest that solutions in cavities in meteorites can provide efficient concentrated biogenic and early nutrient environments, inclu ding high phosphate levels, which may be the limiting nutrient, The re sults also suggest that carbonaceous asteroid resources can sustain so il microbial activity and provide essential macronutrients for future space-based ecosystems. (C) 1997 Academic Press.