Characterization of a new class of deletions of the D region of the bacteriophage T4 genome

Abstract

Mutations in the stp gene of bacteriophage T4 restore the ability of 3′-phosphatase mutants to grow in Escherichia coli strain CTr5x. Spontaneous deletions of the stp and ac genes were isolated by plating 3′-phosphatase mutants on CTr5x in the presence of acriflavine. These deletions, which we designate saΔ mutations, were characterized by physical and genetic mapping and by determination of host range. One third of the saΔ mutations terminate within the D region which is bounded by gene 52 and rIIB, and the remainder extend into rII. An improved map of the D region has been constructed which incorporates a new gene ( pla262) which is required for growth in E. coli CT262. The gene order is gene 52, ac, stp, ndd, pla262, denB, D1, and rIIB. A restrictive host for ndd mutants was also found, strain CT447. With the discovery of restrictive hosts for pla262 and ndd mutants, the D region can no longer be considered completely dispensable.