Abstract: While preventive measures limit the presence of many medically significant microorganisms during spaceflight missions, microbial infection of crewmembers cannot be completely prevented. Spaceflight experiments over the past 50 years have demonstrated a unique microbial response to spaceflight culture, although the mechanisms behind those responses and their operational relevance were unclear. In 2007, the operational importance of these microbial responses was emphasized as the results of an …