Biological Sciences in Space

As pioneer plants mosses are adaptable to extreme environments and are the first to colonize previously uncolonized land. Recently, we designed two centrifuges, MIJ-17 and MK-3, to investigate the effects of long-term cultivation under moderate hypergravity conditions on the growth of mosses. We examined the effects of the vibration generated by these centrifuges on the growth and morphological parameters of the moss Physcomitrella patens, because plants are generally sensitive to vibration. In MIJ-17, random vibration was detected by a micro three-axis acceleration sensor during centrifugation at 2, 5, and 10 G, whereas vibration was negligible in MK-3. Therefore, we compared the growth and morphological parameters of P. patens gametophores cultivated with MIJ-17 and MK-3 at 10 G. The vibration generated by MIJ-17 did not significantly affect the growth and morphological parameters of P. patens gametophores. Thus, we conclude that the vibration of MIJ-17 has a negligible impact on the growth of P. patens gametophores.

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The exact life cycle of cells in a terrestrial cyanobacterium, Nostoc sp. HK-01 which has several different types of cells, was confirmed by microscopic observation. All of types of cells were individually observed during 30-days of liquid incubation. The germination process from akinetes was recognized twice during the incubation period. The contribution of extracellular polysaccharides, EPS, for tolerance to heat in the dried colonies of Nostoc sp. HK-01 was also investigated. The survival rate of dried colonies of Nostoc sp. HK-01 with and without EPS were examined after exposure to temperatures at 100℃. The contribution to heat tolerance of EPS was tested and verified by the cell staining method. The survival rate of both groups of cells, with EPS and without EPS, of Nostoc sp. HK-01 was not remarkably different and they both lived under these conditions for 12 hours. These results indicate that the contribution of EPS to their heat tolerance would be very low. The amounts of sucrose and trehalose in the dry colonies were investigated to determine the contribution to heat tolerance in akinete as a compatible solute. The amount of trehalose was lower than that of sucrose in the dry colonies. It can be assumed that trehalose did not contribute to their heat tolerance.

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