Interference of bacteriophage T4 in the reproduction of RNA-phage M12

Abstract

The RNA-phage M12 is excluded from producing progeny phage following mixed infection with phage T4 (or with T4 am mutants). A small fraction of the infected cells produce some M12 (“escape yielders”), but the burst size is drastically reduced. The failure of most cells to liberate M12 is not due to an inhibition of lysis. A single T4 particle is capable of excluding M12; exclusion occurs in RC str, RC rel and RNase I-less strains. In simultaneous-mixed infection, little or no synthesis of infectious single- or double-stranded M12 RNA occurs; furthermore, the parental M12 RNA does not enter the RNase-resistant structure normally observed in control infections. Exclusion does not appear to involve degradation of the M12 RNA: recovery of radioactivity from cells infected with 32P-labelled M12 alone or with 32P-labelled M12 and T4 is the same and the RNA remains intact. When T4 is added about twenty minutes after M12 infection, little or no synthesis of cellular RNA is observed, whereas M12 RNA synthesis occurs in the absence of infectious phage production. The M12 RNA does not become incorporated into biologically inactive phage particles. Synthesis of M12 coat protein antigen is also markedly inhibited in mixedly infected cells. It is proposed that T4 exerts its control over phage M12 production by interfering with the functioning of M12 RNA in directing protein synthesis.