Effect of prophage W on the propagation of bacteriophages T2 and T4.

Studies have been undertaken to determine whether the temperate phage omega present in Escherichia coli strain W is responsible for the inability of this strain to act as a host for T2 and T4. E. coli WS, cured of phage omega, was sensitive to T2 and T4. Lysogenation of E. coli C and WS with phage omega resulted in loss of ability to plate T2 and T4. However, E. coli K-12 lysogens still served as hosts for the T -even phage. Two of three WS lysogens studied resembled strain W at the biochemical level. They converted about 30% of infecting T2 deoxyribonucleic acid (DNA) to acid-soluble fragments and limited macromolecular synthesis to a few minutes after infection. The third lysogen did not degrade phage DNA, and nucleic acid and protein synthesis continued for some time, although no phage production occurred. It is concluded that phage omega plays a role in the restriction of virulent phage but that it is not the only factor involved. Since acid solubilization was not observed in all cases of phage omega-mediated restriction of T -even phage, a hypothesis for the restriction has been proposed which is based on an alteration in the cell envelope after lysogenation with phage omega.