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Published March 1950 | Published
Journal Article Open

Experiments on photoreactivation of bacteriophages inactivated with ultraviolet radiation

Dulbecco, R.


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 (UV). 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.

Additional Information

© 1950 American Society for Microbiology. Received for publication October 24, 1949. This work was done under an American Cancer Society grant, recommended by the Committee on Growth of the National Research Council, under the direction of Dr. S.E. Luria. The author wishes to express his appreciation to Dr. Luria for facilitating this work materially and for numerous discussions during its progress. The manuscript was completed at the California Institute of Technology. The author also wishes to acknowledge his indebtedness to Dr. M. Delbrück for helpful discussions on the interpretation of the data.

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