Conference Paper

BIOMEX-Desert Cyanobacteria: ground simulations of the EXPOSE-R2 mission

Conference: 12th European Workshop on Astrobiology EANA


Presumably in 2013, new experiments will be performed in space on the EXPOSE facility of the European Space Agency (ESA) attached to the exterior of the International Space Station (ISS). Among the selected experiments for the new mission, called EXPOSE-R2, BIOMEX (BIOlogy and Mars EXperiment) focuses on extremophiles such as lichens, Achaea, cyanobacteria, fungi, bacteria and their cellular components. BIOMEX aims to investigate their resistance when embedded with Martian and lunar mineral analogues. Moreover, resistance of their constituents (biomolecules such as pigments, cell wall components) will be investigated in order to create a biosignature database for the search of life beyond Earth. One of the organisms selected for this experiment is the cyanobacterium Chroococcidiopsis isolated from extremely dry, hot and cold deserts on Earth. Being one of the first phototrophic organisms to appear on the early Earth, its relevance for astrobiology has been assessed in the past years concerning the search for life or future space applications (life support systems, biomining). Indeed its resistance to space and Martian simulated conditions (Billi et al. 2011) as well as real space exposure (Cockell et al. 2011) along with ionizing radiations (Billi et al. 2000) and prolonged desiccation (Billi 2009) have been already reported. To further decipher the molecular basis of its resistance and protection mechanisms and in the preparation of the future EXPOSE mission, ground simulations have been performed and the first results are being exploited. Chroococcidiopsis strain CCMEE 029 (isolated from Negev desert, Israel) exhibits a high survival to the Experiment Verification Tests (EVTs) and Science Verification Tests (SVTs) based on colony forming ability, integrity of cellular components, like presence of undamaged DNA (assessed by PCR genomic fingerprinting) and permanence of photosynthetic pigments (revealed by CLSM). New experimental approaches techniques are being developed in order to complete our understanding of its extreme resistance.