Microbe-I: fungal biota analyses of the Japanese experimental module KIBO of the International Space Station before launch and after being in orbit for about 460 days

Abstract

In addition to the crew, microbes also find their way aboard the International Space Station (ISS). Therefore, microbial monitoring is necessary for the health and safety of the crew and for general maintenance of the facilities of this station. Samples were collected from three sites in the Japanese experimental module KIBO on the ISS (air diffuser, handrail, and surfaces) for analysis of fungal biota approximately 1 year after this module had docked with the ISS. Samples taken from KIBO before launch and from our laboratory were used as controls. In the case of KIBO, both microbe detection sheet (MDS) and swab culture tests of orbital samples were negative. The MDS were also examined by field emission-scanning electron microscopy; no microbial structures were detected. However, fungal DNAs were detected by real-time PCR and analyzed by the clone library method; Alternaria sp. and Malassezia spp. were the dominant species before launch and in space, respectively. The dominant species found in specimens from the air conditioner diffuser, lab bench, door push panel, and facility surfaces on our laboratory (ground controls) were Inonotus sp., Cladosporium sp., Malassezia spp., and Pezicula sp., respectively. The fungi in the KIBO were probably derived from contamination due to humans, while those in our laboratory came from the environment (e.g., the soil). In conclusion, the cleanliness in KIBO was equivalent to that in a clean room environment on the ground.