Abstract
Replication of ΦXtB, a capsid mutant of bacteriophage ΦX174, depends on the host functions directed by the E. coli genes dnaE, dnaF, dnaG, dnaZ, lig and rep. The cellular products of dnaA, dnaB, dnaC(D), dnaI, dnaP, polA, polB and xth genes are, however, dispensable for the viral growth. In these host factor requirements, ΦXtB resembles phages ΦK and St-1, rather than ΦX174. Host ranges of ΦXtB, St-1 and ΦK overlap considerably, and growth temperature of the three phages is somewhat higher than that of ΦX174. Furthermore, ΦXtB is, like ΦK, inactivated by antiserum against St-1. ΦXtB may thus fill an evolutionary gap between the ΦX174 group and the St-1 group.