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**Results and Discussion**  Growth experiments are typically undertaken in liquid media, in part because measuring the optical density of a liquid culture is straightforward. However, liquids present a number of problems in microgravity including the risk of escaping from containment and the fact that if any air were in the tube the culture media would form floating blobs in air. After extensive effort we were unable to design a plate that could safely contain cultures while both allowing accurate OD measurements and allowing permitting  the passage of oxygen. Therefore we turned to solid media which is not traditionally used for OD measurements. A clear agar allows penetration of light and if measurements are taken throughout the well it is possible to extrapolate growth as the bacteria intersect each measurement point. Therefore the OD values shown represent the average of 9 locations throughout each well, with each measurement repeated 25 times in succession. By this measure, the vast majority of the bacteria (45/48) behaved very similarly in space and on earth (Table 1, Figure X). Only three bacteria showed a significant difference in the two conditions; _Bacillus safensis_, _Bacillus methylotrophicus_, and _Microbacterium oleivorans_. However, upon Sanger sequencing the 16S rRNA gene from cultures obtain from the wells on the space plates and the ground plates, we observed contamination of the _B. methylotrophicus_ and _M. oleivorans_ wells and therefore discarded those data. The remaining candidate was _Bacillus safensis_, collected at the Jet Propulsion Laboratory (JPL-NASA) on a Mars Exploration Rover before launch in 2004. As part of standard Planetary Protection protocols, all surface-bound spacecraft are sampled during the assembly process and those strains are then saved for further analysis. We obtained this strain as part of a collection of JPL-NASA strains to send to the ISS (Table 1).