Q-308. Simulated Microgravity Alters Global Gene Expression and Protein Secretion by Staphylococcus aureus

H. Rosado1, M. Doyle1, J. Hinds2, P. W. Taylor1;
1Sch. of Pharmacy, London, UNITED KINGDOM, 2St. George's Hosp. Med. Sch., London, UNITED KINGDOM.

Background: Microbiological monitoring of air and surfaces within the International Space Station has identified bacteria of the genus Staphylococcus as major onboard contaminants. Staphylococcus aureus comprised a significant proportion of these isolates. As previous reports have indicated that microgravity acts as an environmental signal for expression of enhanced bacterial virulence, we examined the effects of simulated microgravity on the virulence properties of S. aureus. Methods: The methicillin-susceptible S. aureus isolates RF1, RF6 and RF11 were grown in a Synthecon High Aspect Ratio Vessel (HARV) under low shear modelled microgravity (LSMMG) with the vessel rotated about the horizontal axis and compared with cells grown under normal gravity in the HARV positioned to rotate about the vertical axis. Global gene expression was determined by DNA microarray analysis and protein secretion examined using two-dimensional gel electrophoresis. Results: Growth in a modelled microgravity environment had an impact on a number of factors associated with the virulence of S. aureus. LSMMG elicited large reductions in protein secretion by the three isolates; in particular isolate RF6 displayed a four-fold reduction in protein secretion. In total, 40 proteins were found to be down-regulated under LSMMG in a highly reproducible fashion. DNA microarray identified significant changes in gene regulation; these were in the main associated with metabolism, transport, stress and virulence; with RF6, the expression of hla and the regulatory system saeR/saeS genes was found to be reduced two-fold. Conclusion: These data provide strong evidence that growth of S. aureus under modelled microgravity leads to a reduction in expression of virulence determinants. There were significant differences between the three isolates in their response to LSMMG.