抄録
Variations in the sensitivities of lysogenic bacteria to X-ray during the growth cycle were investigated using two strains, lysogenic Shigella flexneri strain KA (βL) and nonlysogenic strain KA. The main results obtained were as follows.
(1) The radiosensitivity of the colony forming ability of rapidly dividing cells was markedly higher than that of resting cells in stationary phase.
(2) On the contrary, the sensitivity of the phage inducibility of the lysogenic strain KA (βL) to X-ray was found to be considerably lower when it was in logarithmic growth phase than in stationary phase.
(3) The survival curves measured by counting the visible colonies of both strains were similarly approximately single-hit type, indicated by their exponential inactivation kinetics.
(4) However the radiosensitivity of lysogenic strain KA (βL) for colony formation seemed to be superior than that of nonlysogenic KA, suggesting that the β phage induction may occur independently of the lethal mutation in the irradiated bacteria.
