Chemical studies in host-virus interactions; the mutual reactivation of T2r virus inactivated by ultraviolet light and the synthesis of desoxyribose nucleic acid.

A method has been described for following purine and pyrimidine synthesis in intact cells by measuring the ultraviolet absorption of a bacterial suspension. It has been shown that in cells infected with active virus, the rate of increase of ultraviolet absorption at 2600 A corresponded to that of DNA, although preceding DNA synthesis slightly. The amount of separation of the curves in time was determined by the multiplicity of infection. Under conditions of mutual reactivation of ultraviolet-irradiated virus, DNA synthesis was inhibited but not the increase in ultraviolet absorption. Thus a continuing purine and pyrimidine synthesis was indicated by the increase in this function. When an intact virus particle could be found within these bacteria, however, DNA synthesis began at the rate characteristic of normal infections. Certain peculiarities of lysis in this system were noted. The significance of these observations for various genetic theories has been discussed. It would appear that Luria's hypothesis of independent gene pool synthesis has probably been disproven. It has also been shown that the lesion produced by irradiation of a virus particle with ultraviolet light probably occurs in the DNA of the particle. The validity of these conclusions will depend on a knowledge of the relation of virus protein synthesis to DNA synthesis in this system.