EFFECT OF MITOMYCIN C ON THE CAPACITY OF E. COLI TO SUPPORT MULTIPLICATION OF φA

Abstract

Effect of Mitomycin C treatment on the host cell capacity for multiplication of φA was investigated, taking advantage of Ca²⁺-dependent transfection of the replicative-form DNA. In contrast to uvr⁺, uvrD, and uvrF strains, cells of uvrA, uvrB, or uvrC mutant sufficiently supported the viral multiplication after treatment with 50μg/ml of Mitomycin C. The host capacity of uvrE strain showed an intermediate sensitivity to Mitomycin C. Plaque yield of φA in rec^- strains was, as in rec⁺ uvr⁺ hosts, markedly decreased by pretreatment with Mitomycin C. In contrast with DNA polymerase II, both polymerizing activity and 5′-3′ exonuclease activity of DNA polymerase I were involved in host-cell reactivation for ultraviolet-irradiated replicative form. The capacity to develop φA of polA, polA 107, and resA mutants was, like that of pol⁺ or polB1 strains, conspicuously decreased upon treatment with the antibiotic. Effect of several radiomimetic agents on the host capacity was compared with that of Mitomycin C. In ultraviolet sensitivity of the host capacity, a small difference was observed between uvr⁺ bacteria and uvrA mutant. Infectivity yield of Mitomycin C-treated replicative-form was not particularly affected by uvrA mutation.