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Space radiation was monitored using the R3DR2 spectrometer-dosimeter during the flight outside the Russian “Zvezda” module of ISS in October-November 2014. The instrument was mounted on the ESA EXPOSE-R2 platform. The R3DR2 instrument was first developed and used during the flight of ESA EXPOSE-R platform in 2009-2010 (Dachev et al, 2015a). It is a low mass, small dimension automated device that measures solar visible and ultraviolet (UV) radiation in four channels and ionizing radiation in 256 channels of a Liulin-type energy deposition spectrometer (Dachev et al, 2002). Ionizing radiation was measured and separated in 256 deposited energy spectra, which were further used for determination of the absorbed dose rate and flux. The main results obtained by the R3DR2 instrument are: (1) three different radiation sources were detected and quantified - galactic cosmic rays (GCR), energetic protons from the inner radiation belt (IRB) in the region of the South Atlantic anomaly and energetic electrons from the outer radiation belt (ORB); (2) for the first time in the history of using of the Liulin-type energy deposition spectrometers (Dachev et al, 2015b) an observable flux from solar energetic particles (SEP) was detected in the period 1-4 November 2014; (3) the obtained SEP energy deposition spectra were compared with other spectra to confirm their shape.

国際アストロバイオロジーワークショップ2013（第6回日本アストロバイオロジーネットワーク年次研究会）（2013年11月28日-30日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)（ISAS)）, 相模原市, 神奈川県, International Astrobiology Workshop 2013 (November 28-30, 2013. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000008023, レポート番号: 1026

As part of the PROTECT experiment of the EXPOSE-E mission on board the International Space Station (ISS), the mutagenic efficiency of space was studied in spores of Bacillus subtilis 168. After 1.5 years' exposure to selected parameters of outer space or simulated martian conditions, the rates of induced mutations to rifampicin resistance (Rif(R)) and sporulation deficiency (Spo(-)) were quantified. In all flight samples, both mutations, Rif(R) and Spo(-), were induced and their rates increased by several orders of magnitude. Extraterrestrial solar UV radiation (110 nm) as well as simulated martian UV radiation (200 nm) led to the most pronounced increase (up to nearly 4 orders of magnitude); however, mutations were also induced in flight samples shielded from insolation, which were exposed to the same conditions except solar irradiation. Nucleotide sequencing located the Rif(R) mutations in the rpoB gene encoding the β-subunit of RNA polymerase. Mutations isolated from flight and parallel mission ground reference (MGR) samples were exclusively localized to Cluster I. The 21 Rif(R) mutations isolated from the flight experiment showed all a C to T transition and were all localized to one hotspot: H482Y. In mutants isolated from the MGR, the spectrum was wider with predicted amino acid changes at residues Q469K/L/R, H482D/P/R/Y, and S487L. The data show the unique mutagenic power of space and martian surface conditions as a consequence of DNA injuries induced by solar UV radiation and space vacuum or the low pressure of Mars.

Because of their ubiquity and resistance to spacecraft decontamination, bacterial spores are considered likely potential forward contaminants on robotic missions to Mars. Thus, it is important to understand their global responses to long-term exposure to space or martian environments. As part of the PROTECT experiment, spores of B. subtilis 168 were exposed to real space conditions and to simulated martian conditions for 559 days in low-Earth orbit mounted on the EXPOSE-E exposure platform outside the European Columbus module on the International Space Station. Upon return, spores were germinated, total RNA extracted, fluorescently labeled, and used to probe a custom Bacillus subtilis microarray to identify genes preferentially activated or repressed relative to ground control spores. Increased transcript levels were detected for a number of stress-related regulons responding to DNA damage (SOS response, SPβ prophage induction), protein damage (CtsR/Clp system), oxidative stress (PerR regulon), and cell envelope stress (SigV regulon). Spores exposed to space demonstrated a much broader and more severe stress response than spores exposed to simulated martian conditions. The results are discussed in the context of planetary protection for a hypothetical journey of potential forward contaminant spores from Earth to Mars and their subsequent residence on Mars.

Rifampicin-resistant mutants were collected from the spores of three B. subtilis strains, HA101(HA, repair profecient), TKJ6312 (US, UV-repair defective) and TKJ6412 (RF, recombination defecient) grown after exposure to various radiations and simulated space environments. All of 563 mutations analyzed carried sequence changes in the N-terminal region of the rpoB gene codingfor the subunit beta of RNA polymerase II and belonged to 56 alleles. (1) Most of spontaneous mutants from the three strains belonged to 13 single-base substitution (SBS) alleles, exceptions (50%) of TDS. In HA spores, the allele r201 (CA to TT at 1460) was the most frequent, while in US spores, another allele r210(TC to AA at 1404) was the most frequent. In conclusion, some of the conditions encountered in space environments, such as space vacuum and ionizing radiations, could produce unique mutational signatures in the rpoB gene of B. subtilis spores., COSPAR