[BAO01-P12] Analysis of DNA damage induced by space exposure of Deinococcus radiodurans R1 in Tanpopo mission
Keywords:Panspermia hypothesis, Space exposure experiments, Cell aggregate, DNA damage, Quantitative-PCR
Dried deinococcus cell-aggregates with different thickness were exposed to space (space samples) for about one year. The cells were also stored in the ground laboratory (ground references) and in ISS cabin (ISS references). After exposure or storage, genomic DNA was extracted from each sample and an 887-bp region in the rpoB gene was amplified by q-PCR. Intact DNA (%) was determined from the quotient N/N0, where N = copy number of rpoB gene amplified from DNA of exposed or stored cells and N0 = copy number of rpoB gene amplified from freshly prepared DNA.
Results and Discussion
Cell-aggregates with 100 µm-thickness exposed to space all cells were dead. Intact DNA of the cell-aggregates with 100 µm-thickness exposed to space was less than 1%. On the other hand, Survival fraction in those with 500, 1000 μm-thickness was similar between the ground references and the space samples. The result indicates that UV affected only the surface of the cell-aggregates. Intact DNA showed a good correlation with surviving fraction. We will also report the types and degrees of DNA damage using other methods.
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