RESUMO
Both acridine-sensitized inactivation and mutagenesis in phage sd have been studied and compared with the effect of other mutagens. Inactivation curve was not stictly exponential, with a small shoulder at short light doses and deviation of survival lower than 10(-5). The lethal effect was not reactivated by multiplicity reactivation. Photodynamic damage in phage sd was accompanied by the increase of the rise (but not of the latent) period in the one-step curve of phage multiplication and increase of the burst size. Experiments were carried out at dye concentration of 1-10(-5) M or lower; a strong dark effect of the dye being observed under 2-fold increase of the dye concentration. Plaque-type mutants were formed up to the maximum approximately 1% at the survival approximately 2--10(-5); in comparison with other mutagens photo-sensitized mutagenesis in phage sd was lower. The significant increase in the number of plaque mutants was observed after the illumination of phage fraction surviving the pre-treatment with higher acridine orange concentration (greater than or equal to 2-10(-5)M).