Abstract
Microbe-mineral interactions have become of interest for space exploration as microorganisms could be used to biomine from extra-terrestrial material and extract elements useful as micronutrients in life support systems. This research aimed to identify the impact of space flight on the long-term survival of Cupriavidus metallidurans CH34 in mineral water and the interaction with basalt, a lunar-type rock in preparation for the ESA spaceflight experiment, BIOROCK. Therefore, C. metallidurans CH34 cells were suspended in mineral water supplemented with or without crushed basalt and send for 3 months on board the Russian FOTON-M4 capsule. Long-term storage had a significant impact on cell physiology and energy status (by flow cytometry analysis, plate count and intracellular ATP measurements) as 60% of cells stored on ground lost their cell membrane potential, only 17% were still active, average ATP levels per cell were significantly lower and cultivability dropped to 1%. The cells stored in the presence of basalt and exposed to space flight conditions during storage however showed less dramatic changes in physiology, with only 16% of the cells lost their cell membrane potential and 24% were still active, leading to a higher cultivability (50%) and indicating a general positive effect of basalt and space flight on survival. Microbe-mineral interactions and biofilm formation was altered by spaceflight as less biofilm was formed on the basalt during flight conditions. Leaching from basalt also changed (measured with ICP-OES), showing that cells release more copper from basalt and the presence of cells also impacted iron and magnesium concentration irrespective of the presence of basalt. The flight conditions thus could counteract some of the detrimental effects observed after the 3 month storage conditions.
Highlights
Microorganisms can interact with rocks and minerals to enhance leaching of elements for sustaining their survival and growth
These results indicated that cultivability decreased significantly less during space flight compared to the ground control and that the presence of basalt positively affected cultivability of the ground control
Effect of Space Flight on Physiology The impact of space flight conditions and the presence of basalt on physiological changes within the cells were analyzed with flow cytometry by staining with specific functional dyes
Summary
Microorganisms can interact with rocks and minerals to enhance leaching of elements for sustaining their survival and growth They can impact rock and mineral weathering through production of organic acids and other ligands, which in turn impact mineral solubility, denudation, and speciation (Dong, 2010). Acidophilic iron- and sulfur oxidizing bacteria are used in biomining applications to oxidize copper and gold sulfidic bonds in order to solubilize and recover the economically interesting metals from the ores (Ubaldini et al, 2000) These interactions can lead to the formation of biofilm communities on the mineral surface, in which members will be protected from harsh environments (Harrison et al, 2005)
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