[H-CG30] Closed bio-ecosystems in extraterrestrial environments

[HCG30-02] Low molecular-weight compounds contributing to the dry heat tolerance of the terrestrial cyanobacterium Nostoc sp. HK-01

*Shunta Kimura^1,2, Midori Ong¹, Kaori Tomita-Yokotani³ (1.Graduate School of Life and Environmental Sciences, University of Tsukuba, 2.Japan Society for the Promotion of Science, 3.Faculty of Life and Environmental Sciences, University of Tsukuba)

Keywords:Akinete, Dry heat tolerance, Nostoc sp. HK-01, Terrestrial cyanobacteria

Terrestrial cyanobacteria are useful for enabling bio-chemical circulation in closed bio-ecosystems, which is achieved owing to their photosynthetic and nitrogen fixing ability, utility as a food, and tolerance to harsh environments. Dried colonies of the terrestrial cyanobacterium Nostoc sp. HK-01 have a high tolerance to vacuum, UV, gamma-rays, heavy particle beams, and extreme temperatures. Tolerance to extraterrestrial environments is important for transportation to Mars. Nostoc sp. HK-01 has several different types of cells in its life cycle. The akinete (dormant cell) cell type of in Nostoc sp. HK-01 shows tolerance to dry heat. Some functional substances which provide tolerance against heat exist in the akinete cells. In this study, we investigated a property of low molecular weight compounds, which are accumulated in the akinetes of Nostoc sp. HK-01, to prevent protein aggregation after heating. The results of our study suggest that the compounds function as a compatible solute, which contributes to the dry heat tolerance of the akinetes of Nostoc sp. HK-01. The detailed mechanisms of action of the identified substances would be investigated in future studies.