A terrestrial cyanobacterium, Nostoc sp. HK-01, is a candidate material for introduction to extraterrestrial environments, such as Mars, given its high tolerance to drought and other extraterrestrial environments. Here, we evaluated Nostoc sp. HK-01 as food for future habitation of Mars. We found that wet colonies of Nostoc sp. HK-01 after initiation survived for over 8 years on Martian regolith simulant (MRS), although they did not survive for over 105 days on medium without MRS. Total protein per 100 g of the dried colony of Nostoc sp. HK-01 was approximately 50 g. Increases in biomass proliferation in liquid or on agar medium were determined in six strains of terrestrial cyanobacteria, including Nostoc sp. HK-01, N. commune HK-02, N. commune YK-04, N. punctiforme ATCC 29133, Brasilonema sp. HK-05 and Calothrix sp. HK-06. Nostoc sp. HK-01 grew better compared to the other five strains under both conditions. Following the incubation of Nostoc sp. HK-01, the medium exhibited radical-scavenging activity. Sugar content in the medium after a 1-day incubation of Nostoc sp. HK-01 was one-sixth of its dry weight at initiation. These results indicate that, after liquid incubation, the remaining cells may be used as recyclable materials on Mars.
Viable microorganisms are frequently found in space stations. The unique adaptive ability of bacteria partly depends on horizontal gene transfer among the individual cells. Microgravity, defined as a local environment in a space habitat where gravity seems not to act, is an unexperienced condition for most of Earth’s organisms, and can therefore affect bacterial physiology, gene expression, and gene transfer. The present study evaluates the effect of microgravity on horizontal gene transfer in Escherichia coli. To this end, we compared the transformation frequencies of E. coli under normal gravity and under low-shear modeled microgravity (LSMMG) generated by a high-aspect rotating vessel (HARV). Our results demonstrated that bacterial transformation is not hampered by LSMMG, and the potential risk of bacterial gene transfer during space flight is comparable to that on Earth. Therefore, we should arrest the spread of harmful genes such as toxin-producing and antibiotic resistance genes in crewed space habitats, as well as on the Earth.
The heat tolerance of dry colonies of a terrestrial cyanobacterium, Nostoc sp. HK-01 by exposure to temperatures at 100 °C, the boiling point of liquid water, was examined. The cells of Nostoc sp. HK-01 can live under these conditions for 10 hours. All of the viable cells were akinetes which are dormant cells. Akinetes have a high tolerance to high temperatures. The photosynthetic ability of cells of HK-01 was normal even after the heat exposure. The percentage of decreased water content in the dry colony was 5 percent during the heat exposure for 24 hours. The reasons for the decrease in the percentage of survival rates of colonies under the high heat condition are related to the remaining water in the dry colony, and/or, DNA damage of individual cells. Furthermore, there is a possibility that there are highly tolerant cells in the dry colony since there are cells that survived over 24 hours after the heat exposure.
The 10th Asian Microgravity Symposium was successfully held in Seoul, South Korea. In all, 169 scientists participated from China, Japan, South Korea, Pakistan, Malaysia, and Saudi Arabia, as well as non-Asian countries (United States, Germany, and the Netherlands). This was the first symposium to which our society, the Japanese Society for Biological Sciences in Space joined as a co-organizer of the symposium; 10 members of our society participated in this symposium. Sessions for two different subgroups, life sciences and material sciences, were simultaneously conducted for three days. The various presentations documented the ongoing and future microgravity research and programs in each country, including the future research at the Chinese Space Station. This commentary summarized the historical overview of this symposium and the current status of space life sciences in Asia, and discussed the importance of this symposium.
Life support and effective countermeasures against damaging space radiation for humans on long-duration space missions will be highly dependent on the amount of food and efficient conversion of CO2/O2. The cultivation of fresh vegetables enriched in phytomedicine is an alternative option for keeping crews' health and recycling of CO2 in a closed environment. A whole garlic plant cultured hydroponically is edible and a rich source of medicinal compound, carbohydrates, proteins and vitamins. Garlic plants were cultured for 60 days at 400 (control), 450, 800 and 900 µmol mol-1 carbon dioxide in controlled environment chambers to study growth and ajoene accumulation. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 450 µmol m-2 s-1 PPFD. Fresh and dry mass accumulation of each parts of garlic plants were significantly increased by increasing the CO2 levels from 400 to 900 µmol mol-1. Fresh mass in bulbs, leaves and roots were 28.6, 66.3 and 92.2 g per plant, respectively, and 1.9, 1.8 and 2.0 times, respectively, greater at 900 µmol mol-1 CO2 than at 400 µmol mol-1 CO2. Transpiration rate and stomatal conductance were decreased by increasing the CO2 levels while water use efficiency and relative chlorophyll contents were increased. The concentrations of ajoene accumulation were significantly increased with increasing of CO2 levels from 400 to 800 µmol mol-1 but no significant increase of ajoene accumulation was observed with increasing CO2 level from 800 to 900 µmol mol-1. Total ajoene accumulation in bulbs, leaves and roots were 2.3, 2.6 and 2.6 times, respectively, greater at 900 µmol mol-1 CO2 than at 400 µmol mol-1 CO2. The results indicate that elevated CO2 can increase ajoene accumulation as well as biomass production and water-use efficiency in garlic plants.