Serological study of tail structure and function in coliphages T2 and T4

Abstract

Inactivation of T-even phages can result from reaction of antiserum with either phage tail sheath or tail fibers. At least two different antigenic configurations (epitopes) on the sheath and two on the fibers react with serum causing neutralization of the phage particle. T2 and T4 share one of the sheath epitopes and one of the fiber epitopes, accounting for the serological cross reaction between them. They differ by at least one sheath and one fiber epitope, so that cross reaction is incomplete. A hybrid between T2 and T4, retaining T4 host range characteristics, has T4-specific fibers but T2-specific sheath. A possible third sheath epitope is important to tryptophan activation in phage T4.38. Evidence is presented that the host-range genetic region is the structural gene determining the specific fiber epitope, which is operative in specific adsorption to host bacteria. Other tail components, however, may balance or overcome the specific fiber epitope in its function.