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Methods for the Culture of C. elegans and S. cerevisiae in Microgravity  Thomas Fahlen1, June Sunga1, Jon Rask1, Anna Herrera2, Kitty Lam2, Luke Sing1, Kevin Sato1, Melissa Kirven-Brooks1, and Debra Reiss-Bubenheim3   1Lockheed Martin Space Operations, NASA Ames Research Center, Moffett Field, CA 94035  2 NASA/Ames Internship Program, NASA Ames Research Center, Moffett Field, CA 94035  3NASA Ames Research Center, Life Sciences Division, Moffett Field, CA 94035

   To support the study of the effects of microgravity on biological systems, our group is developing and testing methods that allow the cultivation of C. elegans and S. cerevisiae in microgravity.  Our aim is to develop the experimental means by which investigators may conduct peer reviewed biological experiments with C. elegans or S. cerevisiae in microgravity.  Our protocols and supporting data will enable investigators to grow these organisms for extended periods during which samples may be sub-cultured, collected, preserved, frozen, and/or returned to earth for analysis.  Additionally, we are developing video capability to permit periodic observational analysis of C. elegans behavior on orbit.  Data presented are from initial ground based efforts and include characterization of the growth phenotype of these organisms in liquid medium in OptiCells_.  Our data show that C. elegans grow at a rate comparable to that in a standard culture flask, reach densities of up to 1 x 106 worms/ml in liquid medium in OptiCells_, and may be initiated with as few as 10 worms/ml.   Similarly, S. cerevisiae cultured in YPD in an OptiCell_ grow at a comparable rate to those in a shaker flask and reach a similar final cell density of approximately 5 x 108 cells/ml.  For C. elegans cultures, an air-flow rate of at least 37 feet per minute across the Opticell_ is needed to support optimal growth.  These results suggest that our culture conditions support the growth of C. elegans and S. cerevisiae as well as, or better than, conventional culturing methods.  Finally, safety testing of the OptiCells_ indicates their ability to withstand rapid depressurization and repressurization without bursting or leakage.  This is an absolute necessity to ensure containment of the specimens and media during flight.