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BACTERIAL RESPONSE TO MODELED MICROGRAVITY- A COMPARISON BETWEEN GENOTYPIC AND PHENOTYPIC RESPONSES.      M.A. Juergensmeyer¹, E.M. Mobley¹, and E.A. Juergensmeyer^{2         1}IIT Research Institute, Chicago, IL, and ²Judson College, Elgin, IL.

   A wide variety of mechanical devices have been used on Earth to mimic the environment seen during spaceflight.  While all modeled microgravity (MMG) systems are able to re-create some elements of the spaceflight environment, no single device is capable of truly mimicking spaceflight.  It is, therefore, of interest to the researcher to know which device might potentially be the most similar to spaceflight, and thus, perhaps, the most useful during ground-based studies.

   We have grown Escherichia coli on fast clinostats, slow clinostats, vibrating shakers, and High Aspect Rotating Vessels (HARVs).  Each of these MMG systems provides a different subset of the microgravity environment, and each MMG system results in physiological changes comparable to those seen during spaceflight, e.g. reduced lag phase, higher final cell number, etc.  However, examination of the RNA regulation during growth on these MMG systems reveals that of the four systems tested, the clinostats and linear vibration induce generally the same number of genes and pathways, while HARV-grown cultures are significantly higher numbers of genes.  We therefore chose another physiological test, antibiotic resistance, and determined the change in resistance of bacteria grown on these four MMGs.

   E. coli grown in MMG were challenged with eleven antibiotics of varying modes of action.  Overall, very little significant change in minimal inhibitory concentration (MIC) was seen.  However, vibrated cultures had a slight tendency to be more susceptible to antibiotics than the control, while HARV cultures had a tendency to be more resistant.  The HARV data correlates with an increase in the amount of RNA coding for antibiotic resistance genes seen in the microarray data, although the increase in resistance was not as significant as the array data would have predicted.

Supported by NASA Grant NNA04CC75G