| FY2000 Ground - based Research Announcement for Space Utilization Research Report |
| Research Categories |
| Phase IA Research |
| Research Fields |
| Fundamental Biology |
| Theme |
| Distribution of extremophiles in space environment |
| Name |
| Akihiko Yamagishi |
| Organization |
| Tokyo University of Pharmacy and Life Science |
| Research Term |
| FY1998～2000 |
Japanese  |
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| Distribution of extremophiles in space environment |
| Akihiko Yamagishi, Shiho Itahashi, Haruka Kobayashi, Shin-ichi Yokobori, and Chie Motono
Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachiojishi, Tokyo 192-0392 |
| Summary of Research
Aim of the research Characteristic distribution of microbes is expected in space environment, where dose of radiation is high, pressure is extremely low, and variation of temperature is large. We analyzed the characteristics of the distribution of microbes, especially thermophiles and UV-resistant microbes, in the surface air, in the air at high altitude, and in the space ship Mir. UV-resistant microbes were selectively isolated from the samples corrected from these environments. Sequences of 16SrRNA and other bacteriological characteristics of the isolates were analyzed. Knowledge about the distribution of microbes in such environment is necessary for designing space utilisation programs. Another aim of the research is the experimental estimation of the possibility of distribution of microbes through high altitude and space. Methods Equipment to collect air dusts from outside of an aircraft was designed and built. Air dust was collected on membrane filters using the equipment on an aircraft. The filters were placed on solid media and incubated at 33 or 37oC. Colonies were counted after 2- to 7-day incubation. DNA extracted from the strains isolated was used for PCR amplification of 16SrRNA gene. The PCR products were cloned and sequenced and compared with known sequences in databases. Results UV-resistant clones selected from the microbes isolated from the samples corrected in the space ship Mir, showed twice UV-resistance of that of Escherichia coli and Bacillus subtilis. Though the radiation in the space ship is higher than that on the surface of earth, the intensity does not seem to be high enough to select UV-resistant microbes. Microbe density of about one CFU per m-3 was detected in the air collected by using an aircraft. The 16SrRNA sequences of the two isolates suggested that these clones are new species in the genus Deinococcus. These two isolates showed higher UV-resistance than that of Deinococcus radiodurance, which is the most UV-resistant microbe. High UV-resistance of the species has been suggested to be the side effect of its desiccation resistance. However the current results suggest that the high UV-resistance of these species may be evolved because of the advantage for distribution though high altitude. Extreme thermophiles and ultra thermophiles were not detected in the samples collected on the surface of earth or in that collected using an aircraft. Thermophiles were not detected in the samples collected around the Miyake Island. Smokes evolved from the volcano may not contribute much to the distribution of thermophiles. Possibility of space utilization experiments We found UV-resistant microbes at the altitude of 12 km. The cell density was roughly 1 CFU/m-3 (mass volume). It is necessary to estimate the cell density at higher altitude. Then it will become possible to speculate the cell density of UV-resistant microbes at the altitude of space station. However, the equipment used for collecting dust samples must be redesigned for the use in the atmosphere of lower pressure. Exo-terrestrial origin of life has been proposed. If we could find microbes at the altitude of space station, it supports the higher possibility of interplanetary movement of life. When designing the mission of searching for life forms in other planets, possible presence of terrestrial type life form has to be considered. List of Publications
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