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The influence of antibiotics on bacterial motility and its implication for drug efficacy in microgravity.    A.R. Stanczyk¹ and D.M. Klaus²

¹University of Michigan, Flint, MI, 48502 and ²University of Colorado, Boulder, CO 80309.

   Understanding in vitro bacterial response to antibiotics in a microgravity environment is an important step toward the goal of minimizing astronaut health risks. Previous studies have shown that bacteria cultured in space are able to proliferate in normally inhibitory concentrations of antibiotics. Identifying the cause of this reported behavior has proven difficult, however, due to the complex interactions of gravitational influence on living organisms. Research aimed at identifying and isolating independent variables can help to elucidate the responsible mechanisms. This project focuses on the study of one such variable, cell motility. It is hypothesized that antibiotic effectiveness in space is reduced as an indirect consequence of bacterial motility inhibition. The rationale behind our hypothesis is based on related research suggesting that less motile bacteria exhibit more pronounced responses to microgravity in general than highly motile ones, purportedly due to extracellular mass transport factors. Motility of E. coli (ATCC 4157) was evaluated as a function of radial growth from a stab culture inoculated on semi-solid agar using different nutrient sources, both with and without Streptomycin. Results are correlated to literature describing antibiotic experiments conducted in space. (Supported by UM-Flint Honors Scholar Program and BioServe Space Technologies, NASA NCC8-242)