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POEMS: Passive Observatories for Experimental Microbial Systems

M.S. Roberts¹, M.N. Birmele¹, D.W. Reed², and T.E. Mortenson². ¹ Dynamac Corporation, and ² Bionetics Corporation, Space Life Sciences Lab, Kennedy Space Center, FL.

   Passive Observatories for Experimental Microbial Systems (POEMS) is a NASA spaceflight experiment to the International Space Station launched on shuttle mission STS-121. POEMS utilizes the BRIC-Opti (Biological Research in Canisters for OptiCells™) payload hardware to explore the relationship between recombination (horizontal gene transfer or HGT) and sequence divergence in the genetic transformation of a naturally competent population of Bacillus subtilis cultivated in microgravity on ISS and shuttle in the presence of DNA from different donor strains. Previous ground-based studies in B. subtilis and other bacteria have demonstrated that the frequency of recombination is negatively correlated with the level of sexual isolation at a locus, i.e. recombination is reduced by a factor of 10 for every 1% of sequence divergence between donor and recipient loci. Recombination is not a significant force of cohesion within bacterial species, but HGT is the primary mechanism for acquisition of new functions in bacteria.  In the space environment where reduced gravity and elevated radiation have multiple effects upon cellular and community-level processes, both the extent and rate of horizontal gene transfer among bacteria are affected. By extension, the ability of bacteria to acquire new functions, exploit novel environments, and form new ecological species may be accelerated in space because of elevated rates of genetic transfer, relaxed constraints in mismatch repair, or other responses to microgravity. We will present an operational assessment of BRIC-Opti hardware performance and preliminary phenotypic and genotypic data from the POEMS experiment that reports on the effect of microgravity on the growth, diversity, recombination, and evolution of B. subtilis in an HGT permissive environment.