sentences:  "Staphylococcus aureus" and "Aspergillus" spp have commonly been isolated from the air and surfaces during several space missions.The microbes do not sediment in microgravity which results in persisting airborne aerosols and high microbial densities in-cabin air in particular if the cabin air filtering systems are not well maintained.During one mission an increase in the number and spread of fungi and pathogenic streptococci were found.