Japan Geoscience Union Meeting 2018

Presentation information

[EE] Evening Poster

B (Biogeosciences) » B-AO Astrobiology & the Origin of Life

[B-AO01] Astrobiology

Tue. May 22, 2018 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Hikaru Yabuta(Hiroshima University, Department of Earth and Planetary Systems Science), Seiji Sugita(Department of Earth and Planetary Science, Graduate School of Science Sciece, The University of Tokyo), Misato Fukagawa(名古屋大学, 共同), Fujishima Kosuke(Tokyo Institute of Technology, Earth-Life Science Institute)

[BAO01-P13] Mutation analysis of the rpoB gene in the radiation-resistant bacterium, Deinococcus radiodurans R1 exposed to space

*Daisuke Fujiwara1, Yuko Kawaguchi1, Yuka Togashi1, Iori Kinoshita1, Jun Yatabe1, Issay Narumi2, Hirofumi Hashimoto3, Shin-ichi Yokobori1, Akihiko Yamagishi1 (1.Tokyo University of Pharmacy and Life Sciences, 2.Toyo University, 3.ISAS/JAXA)

Keywords:DNA damage, Deinococcus spp., International Space Station, Mutation, rpoB gene, Space

To investigate the microbial viability and their DNA damage, the radiation-resistant bacteria Deinococcus spp. have been exposed at the Exposure Facility of the International Space Station (ISS) in Tanpopo mission since May 2015 [1,2]. The Exposure Panels (EPs) harboring dried-deinococcal cells returned to the ground on October 2016 after about one-year exposure. We analyze the survival rate and DNA damage of dried deinococcal cells using pulsed-field gel electrophoresis, quantitative-PCR and mutation assay. The antibiotic rifampicin binds the RNA polymerase β-subunit, which is encoded by the rpoB gene, and inhibits the initial step of transcription. Certain mutations in the rpoB gene confer rifampicin resistance [3]. Based on these characteristics of the rpoB gene, we determined mutant frequency and the mutation spectrum in the D. radiodurans rpoB gene exposure to space. From these mutation data, we estimated major DNA damage induced by the space environment.

D. radiodurans R1 cell-suspension was dropped in the wells of aluminum plates and was dried under vacuum (vacuum-dried). The dried cells were exposed to space, stored in ISS cabin or in the ground laboratory. After exposure experiment, the cells recovered from each well were used to inoculate 10 ml of mTGE medium and cultured until OD590 nm reached between 0.7 and 3.0. The cell suspension was plated on mTGE agar containing 50μg/ml rifampicin to determine the number of rifampicin resistant cells (RifR), and on mTGE agar without rifampicin to determine the total number of viable cells.

We also determined the sequences of the rpoB gene extracted from RifR. The rifampicin resistant mutation frequencies of the space exposed D. radiodurans R1 cells and those of the ground control were comparable (Fig. 1). The result suggested that the effect of UV for dried-cells exposure to space was less. Further, we will report and discuss the rifampicin-resistant spectra in the rpoB gene in rifampicin-resistant cells exposure to space, stored in ISS or in ground laboratory.

[1] Yamagishi, A. et al., (2007) Bio. Sci. Space 21: 67−75.
[2] Kawaguchi et al., 2016, Astrobiology 16 : 363−376.
[3] Campbell, E. A. et al., (2001) Cell 104: 901−912