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Vibration Without Oxygenation Affects Bacterial Growth. E.A. Juergensmeyer 1, M.A. Juergensmeyer 2, and E.S. Nelson 3.1 Judson College, Elgin, IL, 2 IIT Research Institute, Chicago, IL, 3 NASA-Glenn Research Center, Cleveland, OH

   Bacteria in liquid media are routinely shaken, with the aim of aerating the cultures. These shaken cultures have a shorter lag phase, increased growth rate, and higher cell number than stationary cultures, which is attributed to oxygenation. Bacterial cultures flown on the Space Shuttle have been demonstrated to have a shorter lag phase, increased growth rate, and higher cell number than ground controls, even though the cultures were sealed against ambient air. We hypothesize that the vibration inherent in space platforms, without concurrent oxygenation, induced the changes in the growth rate. E. coli, B. subtilis, P. aeruginosa, or S. aureus cultures were loaded into 10-ml syringes, and either sealed or allowed exposure to ambient air. The cultures were then placed in a single-axis shaker bath (shaken), or into an incubator (stationary). Growth and dissolved oxygen consumption were monitored.  In all four species tested, shaken cultures exhibit a shortened lag phase, an earlier and sometimes steeper exponential phase, and an earlier stationary phase than stationary cultures. These results are independent of the availability of ambient air, and the dissolved oxygen consumption in sealed syringes is not significantly different between shaken and unshaken cultures. These results indicate that shaking alone, without concurrent oxygenation, affects the growth of bacteria.

(Supported by NASA NAG-1512)