The functioning of T-even phages with unglucosylated DNA in restricting Escherichia coli host cells

Abstract

The DNA of the T-even bacteriophages contains glucose bound to the pyrimidine base 5-hydroxymethylcytosine. Modified forms of T-even phage, designated T ∗ phage, which contain little or no glucose, are produced by growth in certain bacterial mutants blocked at some step in the synthesis of uridine diphosphoglucose. The T ∗ phage is able to grow on some strains of Shigella (permissive hosts) but grows poorly or not at all on various strains of Escherichia coli (restrictive hosts). Evidence is presented that the DNA of T ∗ phage undergoes extensive degradation to acid-soluble fragments following infection of restricting E. coli cells, whereas infection of E. coli with wild-type phage, or of Shigella with T ∗ phage, causes very little degradation of phage DNA. T ∗ phage can perform certain functions after infection of restricting hosts. In these respects the T ∗ forms of phages T2, T4, and T6 differ to some extent. Also, phage T ∗2 can undergo extensive growth activation in E. coli cells in multiple infection, whereas T ∗4 and T ∗6 do not exhibit this multiplicity activation. In mixed infection of E. coli B with the mutant T4 am122, unable to induce synthesis of the enzyme deoxycytidylate-hydroxymethylase, T ∗2 and T ∗6 are capable of complementing the missing function, whereas T ∗4 cannot. Evidence is presented that T ∗ phages can in fact direct synthesis of some early enzymes in restricting hosts. Despite the occurrence of some early enzyme synthesis, phage DNA synthesis does not occur after infection of restricting bacteria with T ∗ phage except in the cells where restriction fails. The ability of permissive hosts to support replication of T ∗ phage is not due to an initial glucosylation of the incoming nonglucosylated DNA.