Preliminary study on synchrotron X-ray irradiation against hypothetical intra-meteorite/-comet habitable zones

Microbial cells were irradiated with high-dose X-ray (0.2 nm, 500 R/s) for 0 to 5 min to examine their survivability based on the biological 'energy currency', i.e., Adenosine 5'-Triphosphate (ATP), and the Colony-Forming Units (CFU). The well-known radiation-resistant bacterium, Deinococcus radiodurans, and the normal and mini cells of Escherichia coli X-1488 were used for the irradiation tests. Minicells are known to lack genomic DNA, and were thus used to examine the effect of X-ray on non-DNA damages, while X-ray causes indirect (e.g., via OH-radical formation) damages to DNA. The results were: (1) ATP showed highest survivability in the D. radiodurans cells, followed by the normal E. coli cells; (2) CFU of D. radiodurans showed highest survivability, too; and, (3) ATP and CFU of minicells showed rapid decrease despite absence of DNA to-be-damaged by X-ray irradiation. These results suggest that non-DNA damages (probably damages against proteins and/or membrane) affect the viability of minicells. Direct effects of X-ray irradiation against non-cellular ATP and other biomolecules should be assessed in future studies.
資料番号: AA0063349116