Spaceflight and spaceflight analogue induced responses in gram positive bacteria

The potential alterations in the disease-associated characteristics of Gram positive organisms during spaceflight missions are of great importance for future human exploration efforts. Gram positive organisms, especially Staphylococcus species, are the most prevalent species isolated from the air and surfaces of spacecraft vehicles. The frequent isolation of the opportunistic pathogen, Staphylococcus aureus, from the environment of the International Space Station (ISS) is not unexpected, as 30-50 % of healthy adults on Earth are colonized with this organism. Passage of these organisms between crewmembers is common as demonstrated by a genetic comparison of S. aureus strains isolated from crewmembers aboard the Mir space station. Microbial monitoring also indicated the presence of Streptococcus species aboard the Russian space station Mir and from air samples collected during Space Shuttle missions. While S. pneumoniae has not been isolated from spacecraft or from a crewmember after flight, this opportunistic bacterium has been isolated after nasopharyngeal sampling from a shuttle crewmember immediately before flight. As opportunistic pathogens, such as S. aureus and S. pneumoniae, are likely to be carried as part of the normal flora of a crew and may exploit a declining immune system, understanding the mechanisms behind the disease causing potential of Gram positive organisms has tremendous implications for the spaceflight crew, as well as advancing our knowledge of disease-causing mechanisms on Earth.