Investigation of Nostoc sp. HK-01, Cell Survival over Three Years during the Tanpopo Mission

Kaori Tomita-Yokotani*, Shunta Kimura, Midori Ong, Miku Tokita, Hiroshi Katoh, Tomoko Abe, Hirofumi Hashimoto, Kintake Sonoike, Masayuki Ohmori

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The survival of the terrestrial cyanobacterium Nostoc sp. HK-01 was tested as part of the Tanpopo mission experiment, which was conducted both outside and inside the International Space Station (ISS). The selection of Nostoc sp. HK-01 was based on the results of on-ground experiments that demonstrated that the cyanobacterium can survive simulated space environments. This study verified cell survival after exposure to the outside environment in low Earth orbit (LEO). We examined the cellular tolerance of Nostoc sp. HK-01 simultaneously outside and inside of the ISS over a 3-year period. After the experiments were conducted, we confirmed cell viability by fluorescein diacetate (FDA). Cell growth abilities for 3 years without sunlight in space-vacuum-exposed cells were not significantly different from those of cells kept in the dark of control cells in the ISS and on the ground. Though a few light-exposed cells in space vacuum survived outside the ISS after 3 years as judged by FDA staining assay, the survival could not be verified by testing the growth ability due to an insufficient number of cells. To the best of our knowledge, this is the first pure strain of Nostoc sp. HK-01 that survived in a space environment on the inside and outside of the ISS with and without sunlight for more than 3 years (1126 days).

Original languageEnglish
Pages (from-to)1505-1514
Number of pages10
Issue number12
Publication statusPublished - 2021 Dec 1


  • Cyanobacteria
  • Environmental tolerance
  • Nostoc sp. HK-01
  • Space
  • Tanpopo mission

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Space and Planetary Science


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