Experiments on photoreactivation of bacteriophages inactivated with ultraviolet radiation.

Kelner (1949), working with conidia of Streptomyces griseus, discovered that light belonging to the visible range is capable of reactivating biological material that has been rendered inactive by ultraviolet radiation (WJY). Shortly after Kelner's discovery was known, a similar phenomenon in bacteriophages (bacterial viruses) was observed by accident. Plates of nutrient agar containing UV-inactivated phage and sensitive bacteria had been left for several hours on a table illuminated by a fluorescent lamp. After incubation it was noticed that the number of plaques was higher on these plates than on similar plates incubated in darkness. A short report of this phenomenon of "photoreactivation" (PHTR) has already been published (Dulbecco, 1949). The present paper contains the results of a first group of experiments concerning PHTR of seven bacteriophages of the T group active on Escherichia coli, strain B.