Weightlessness, cosmic radiation and other space flight related conditions may adversely impact the physiology and immune status of the crew. Since microorganisms will surely be present in space habitats, the effects of space on microbial metabolic and physiologic functions will depend upon environmental conditions, types of organisms, and the duration of the flight. Because humans will conduct long-duration space missions, space microbiology must address the effect of alterations in microbial function during space flight. Even innocuous microorganisms and endogenous flora may become etiologic agents for disease during long missions. The microbial population in the closed environments of spacecraft may also become a source of toxic metabolites or the biodegradation of materials.
This paper reviews studies concerning microbial behavior in closed environments, simulated microgravity, and actual space flight. Growth, physiology, subcellular structure, and antibiotic-sensitivity are described. Although the results of studies performed to date are occasionally contradictory, it is clear that the interaction of microorganisms with the space flight environment, including human, animal, and botanical inhabitants, must be investigated in order to ensure the safety of the crews and the integrity of the spacecraft environment.