Evidence from the International Space Station suggests microbial populations are rapidly adapting to the spacecraft environment; however, the mechanism of this adaptation is not understood. Bacteriophages are prolific mediators of bacterial adaptation on Earth. In this study, researchers including School of Biological Sciences Ph.D. student Iris Irby, survey 245 genomes sequenced from bacterial strains isolated on the International Space Station for dormant (lysogenic) bacteriophages. The results correlate microbial adaptation in spaceflight to bacteriophage-encoded functions that may impact human health in spaceflight.