Microgravity, bacteria, and the influence of motility

Space microbiology studies date back to the 1960s, with most investigations reporting that increased bacterial populations occur in flight compared to ground controls. Several exceptions to these findings, however, have created controversy and complicated explanations of how, or whether, microgravity affects microorganisms. Upon closer examination of the literature, we identified a trend relating cell motility to experimental outcome. Related studies conducted in microgravity analog devices, such as the clinostat or rotating wall vessel bioreactor, further corroborate this trend. We review the literature regarding bacterial growth experiments conducted in space (and using microgravity analogs) and analyze the influence of bacterial motility.