Transducing fragments in generalized transduction by phage P1: II. Association of DNA and protein in the fragments

Abstract

The transducing and infective particles of phage P1 were differentially labelled with different isotopes by growing phage P1 on [ 3 H]thymidine-labelled Escherichia coli in a medium containing 32 PO 4 . The density of DNA of the transducing particles was 0·004 g cm −3 lighter than that of the bacterial DNA, but increased to that of the bacterial DNA on treatment with proteolytic enzymes, suggesting the association of protein to the DNA. The DNA-protein linkage was labile to alkaline buffer of pH 10·0 at 37°C for 60 minutes and to shearing force, but relatively stable to a buffer of pH 8·8 at 37°C for 60 minutes. The linkage was not dissociated by the treatment with 6 M -caesium chloride for 48 hours or with 1 % formaldehyde (pH 7·0) at 93°C for 10 minutes. The properties of the DNA-protein linkage are discussed.