R factor-mediated polarized chromosomal transfer in Escherichia coli C

Five transferable drug resistance factors (R factors) with the ability to bring about chromosomal transfer in Escherichia coli C were investigated with respect to the direction and origin of chromosome transfer. They were found to constitute two groups, both with a clockwise direction of transfer. One group has its origin of transfer between arg and pro, and the other group has its origin of transfer between try and man on the E. coli C chromosome. With one R factor in particular, the rapid increase in the production of recombinants was followed by a decrease in numbers as mating was prolonged.