Bioassays for validation of ground-based microgravity simulators

Well defined and reproducible conditions are a prerequisite for platforms such as clinostatsand Random Positioning Machines(RPM) in order to provide simulated microgravity and to prepare space-based experiments. To visualize potential non-gravitational cellular responses during microgravity simulation, we applied the dinoflagellatePyrocystis noctiluca as a highly sensitive reporter organism. This organism responds to shear stress with detectable bioluminescenceemission. Pyrocystis noctiluca was exposed to different microgravity simulations while varying operational modes. With cells in a RPM rotating around two axes with random velocities and directions, we observed significantly greater mechanical stress compared with clinostatexperiments applying constant rotation around one axis. Thus, we conclude that in contrast to RPM, one axis clinorotation induces substantially less non-gravitational responses through shear forces. Therefore, we apply clinostatsas our preferred and validated method for the simulation of microgravity in ongoing cellular experiments. Examples will be presented.