放射線抵抗性細菌の放射線殺菌における細胞質ターゲットの重要性について

抄録

Micrococcus radibduranswhich was isolated from canned meat by Anderson et al shows extreme resistance to both ultraviolet light and ionizing radiation. Although the mechanisms of such high resistance are not clear, radiation damages in DNA may be repaired during postirradiation incubation. At relatively higher doses other cellular damages would become critical for viability if repair system for DNA came into play and others were not repaired. We had studied the relationship between changes in survivals and biosynthetic activities for macromolecules in cells. After irradiation with 2×10⁴ rads by ⁶⁰Co γ-rays, no differences in numbers ofviable cells, ¹⁴C-amino acids incorporation into protein and ³²Pi dncorporation into RNA and DNA fraction from non-irradiated control during postirradiation incubation were found. Biosynthetic activities of protein, RNA and DNA were inhibited to the same extent at the dose of 3.5×10⁵ rads (Fig.2 (B) -Fig.5 (B)) though the viable counts were not reduced (Fig.1). At the higher dose of 8.0×10⁵rads, which gave about 3% survivals, incorporations of these labelled precursors into each fraction were inhibited intensely. These results on M. ractiodurans. are different from those as reported with E.coli that synthesis of DNA is considerably prevented by the irradiation while protein and RNA are synthesized at normal rate. Further studies on radiation effects on macromolecular synthesis in radioresistant bacteria are now under way in this laboratory in the hope of elucidating their radiation resistance.