Seven years of Progress in Determining Fungal Diversity and Characterization of Fungi Isolated from the Japanese Experiment Module KIBO, International Space Station

Microbiol Immunol. 2021 Jul 12. doi: 10.1111/1348-0421.12931. Online ahead of print.

Abstract

The International Space Station (ISS) is a closed facility that orbits the earth carrying not only its crew but also microorganisms. We have participated in microbiota analysis projects for the Japanese Experiment Module KIBO, ISS (operations nomenclature: Microbe-I, II, III, and IV) and were in charge of fungal screening. The interior of KIBO was sampled using swabs and microbe detection sheets (MDS) for fungal detection. The dominant genera obtained by culture were Aspergillus and Penicillium. DNA analyses of the fungal biota using a clone library showed that KIBO was dominated by Malassezia, a fungal inhabitant of human skin. Three fungal species, Aspergillus sydowii, Penicillium palitans, and Rhodotorula mucilaginosa, which grew under microgravity in KIBO were observed under field emission scanning electron microscopy (FE-SEM) on the ground. No novel phenotypic characteristics were noted. The results of antifungal susceptibility testing of all isolates did not differ significantly from previous reports of corresponding fungi. In Microbe-I (August 2009), MDS were culture negative, while in the next stages the CFU of MDS were 10 for Microbe-II (February 2011), 24 for Microbe-III (October 2012), and 151 for Microbe-IV (February 2016). These results indicated that fungi inside KIBO are increasing and expanding over time, and therefore continuous surveillance is crucial. This article is protected by copyright. All rights reserved.

Keywords: Aspergillus; International Space Station; Penicillium; Rhodotorula; fungal diversity.