A Growth-Delaying Effect of Ultraviolet Radiation

Abstract

When unrelated bacterial viruses on the common host, Escherichia coli B, were subjected to u.-v. irradiation, they showed different rates of inactivation, the virus of largest particle size being most rapidly inactivated. Another effect is a delay in the growth of the surviving particles: on a sensitive host the adsorption and burst size were normal but the minimum period between infection and lysis was increased as was the spread in values of the interval for individual cells. The growth-delaying effect is non-hereditary and differently pronounced for different viruses, being more closely related to the total time of irradiation than to the extent of in-activation. Since the delay must be brought about by the action of quanta which have not acted lethally, and since the effect is progressive, it is reasoned that it results from a cumulative effect of u.-v. quanta adsorbed by the virus particles. No similar effect was found on vims particles which had survived x-ray radiation. This is explained by the fact that, for ionizing radiation, nearly each act of absorption by a virus particle is effective in producing inactiva-tion: the surviving particles are likely not to have absorbed any radiation at all.