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Differences in Gene Regulation in E. coli Grown on Four Common Modeled Microgravity Systems.    E.A. Juergensmeyer¹, M.A. Juergensmeyer² and E.M. Mobley²

¹Judson College, Elgin, IL, and ²IIT Research Institute, Chicago, IL.

   Bacterial responses to spaceflight are mimicked on the ground using modeled microgravity (MMG). A variety of different MMG systems exist, and cultures grown in each system are capable of demonstrating physiological responses similar to those seen in flight culture, such as increased growth rate and changes in antibiotic resistance.  However, these systems are rarely compared to each other, and it is not known which MMG is the most similar to spaceflight.  We have grown E. coli in various MMG systems, isolated the RNA from these cultures at mid-log phase, and analyzed the gene expression patterns of the cultures using Affymetrix microarrays.  While there are differences between the various growth systems, certain pathways seem to be uniformly down-regulated by MMG, including sugar transport and the nitrogen metabolism pathways.  Slow clinorotation is extremely different from the other treatments, resulting in over 300 genes differentially regulated, the majority of which were up-regulated.  These results indicate that a profound difference in response exists to various modeled microgravity systems and that the choice of a modeled microgravity system for ground research may be dictated by the aspect of the microgravity environment in question.