The effect of superinfection by T4r+ coliphage on the deoxyribonucleases of induced Escherichia coli Y10 (λ)

Abstract

In studying the Escherichia coli Y10 (λ)-T4r+ coliphage system, it was found that T4 excluded intracellular lambda, or lambda excluded T4, depending upon the experimental conditions. Either event was correlated with a significant increase in the specific activity of free intracellular DNase (deoxyribonuclease). During the first 20 minutes after induction of lambda by ultraviolet light, there was no increase in DNase specific activity and the cells responded to T4 as if they were non-induced. Adsorption of T4, or of T4 inactivated by ultraviolet light, led to a rapid increase in free intracellular DNase, the arrest of lambda replication, and infection of the cells by T4. From 20 to 60 minutes after induction there was a progressive increase in free intracellular DNase, accompanied by an increasing ability of the cells to resist T4 infection.The RNase (ribonuclease) treatment of all cellular extracts, whether from normal cells or from cells infected with T4 or lambda, led to a considerable enhancement of DNase activity. This treatment showed that an increase in total DNase activity occurred by 40 to 60 minutes after lambda induction, but failed to reveal any such increase in total DNase activity resulting from successful T4 superinfection.