Genetic analysis of the recJ gene of Escherichia coli K-12.

An insertion of transposon Tn10 was isolated in a gene essential for the RecF pathway of recombination. This mutation and six other previously isolated rec mutations, including one in the recJ gene, were mapped to 62 min on the Escherichia coli chromosome. All seven mutations were examined for their effects on recombination and UV survival in several genetic backgrounds. Although all affected the RecF, and not the RecBC, pathway of recombination, they could be separated into two classes: four severely reduced UV survival and three did not. In addition, whereas the effects of the former class appeared to be nearly equivalent in recB recC sbcA and recB recC sbcB mutant backgrounds, the latter class affected recombination differentially. The latter class was found to be either "leaky" or temperature-sensitive mutations. Transductional complementation assays indicated that representative members of each class were mutations in the same gene, recJ. Possible explanations for the differences in phenotypic effects produced by these recJ mutations are discussed.