Abstract
The effect of R factors on the process of hybridization between Escherichia coli and Shigella flexneri were investigated. All of the R factors which were confirmed to be ri+ in crosses between E. coli strains showed marked suppression of hybridization (ri means an agent determining the effect of recombination interference). Suppression was not observed, however, when the male strains of E. coli were infected with ri- R factors. The extent of the suppression of hybridization by ri+ R factors was similar to that of recombination interference in crosses between E. coli strains. From these results, a possible mechanism of recombination interference was discussed.
