Isolation and characterization of an Escherichia coli bacteriophage requiring cell wall galactose

A new coliphage, designated U3, has been selected for the ability to discriminate the presence of galactose in the cell wall of Escherichia coli. U3 attacks E. coli K-12 cells that are able to incorporate galactose into their cell walls, but mutants blocked in the synthesis of uridine diphosphogalactose, the precursor of cell wall galactose, are completely resistant to the phage. U3 is a small, tail-less, approximately spherical phage resembling phiX174 in its physical properties. Its diameter by electron microscopy is 21 to 22 nm, and its particle weight is approximately 4 x 10(6) daltons. Like phiX174, U3 appears to have a single-stranded deoxyribonucleic acid genome and has at least four cistrons.