ABSTRACT
DNA-DNA hybridization was used to demonstrate that the substituted DNA in the bacteriophage lambda recE (formerly called lambda reverse) is homologous to DNA at the rac locus in Escherichia coli. Strains that are rac- do not contain appreciable amounts of this DNA, and it is lost from a rac+ episome (F' 123) after transmission to a rac- recipient. This is consistent with the proposal that the rac locus contains a cryptic prophage (Low, 1973).
Subject(s)
Bacteriophage lambda/genetics , DNA, Bacterial/genetics , DNA, Viral/genetics , Escherichia coli/genetics , Conjugation, Genetic , Genes , Genotype , Nucleic Acid Hybridization , Phenotype , Recombination, GeneticABSTRACT
Induction of prophage P2sig5 at 42 degrees caused replication of the bacterial chromosome in a dnaA mutant of Escherichia coli. The P2sig5 is integrated in this strain near the metG locus, which is at min 47 on the genetic map. The regions of the chromosome replicated after prophage induction have been determined by means of DNA-DNA hybridization with various DNAs obtained from Proteus mirabilis/E. coli F' merogenotes and from lambda specialized transducing phage. The replication was initiated at the prophage site and was bidirectional. Most of the replication occurred in a counterclockwise direction on the genetic map, and the replication quickly proceeded to the aroD locus (min 37). The replication forks were retarded between aroD and rac (min 31) loci, although the rac locus was finally replicated. A more severe inhibition of replication occurred between the rac and trp (min 27) loci. It is proposed that the replication terminus is near the rac locus and that the terminus inhibits replication forks.
