Body of Abstract: On Earth, plants benefit from a diverse microbiome, which can improve growth and help manage both biotic and abiotic stress events. On the International Space Station (ISS), plants face numerous stressors of both types, which arise directly and indirectly from the microgravity environment. Examples include excess water due to lack of transpiration and opportunistic fungal infections. Despite attempts to sterilize everything launched, plants grown aboard the International Space Station (ISS) have been shown to possess diverse microbiomes which we have previously mined for plant growth promoting bacteria (PGPB). PGP phenotypes from this microbiome include ACC deaminase activity, indole production, siderophore production, and phosphate solubilization. However, these phenotypes were identified in experiments performed on Earth and may not reflect the phenotypic benefits these organisms may confer to plants in the spaceflight environment. We propose to study the bacteria identified through these screens to understand their effects on plants in a simulated microgravity environment. In this study, PGPB from the ISS Veggie system have been used as inoculants on ISS relevant plants such as Lactuca sativa (OutREDgous lettuce) grown on a random positioning machine.