The transfer of material during mating in Escherichia coli: Transfer of DNA and upper limits on the transfer of RNA and protein

Abstract

A procedure is described for measuring the transfer of molecules from cell to cell during bacterial conjugation. Phage-resistant radioactive donor cells are mated with phage-sensitive non-radioactive recipients. After mating, the recipient cells are disrupted by lysis-from-without with bacteriophage T6 and the lysates are filtered through Millipore niters. Radioactivity, which has been transferred from donor to recipient during mating and is released by lysis, is measured in the filtrates. By using different 14 C-labelled materials the transfer of various cellular components can be measured. Transfer of DNA from male to female E. coli was measured using [ 14 C]thymidine as a specific DNA label. Hfr males transfer about 9% of their DNA per recombinant during 90 min of mating in agreement with the expectations from genetic experiments. F′ 13 males transfer about 3% of their DNA per recombinant in agreement with the genetic size of the extrachromosomal fragment. There is no significant transfer from male to male or female to female. There is no significant transfer from Hfr donors of either RNA (using [ 14 C]uracil) or protein (using [ 14 C]proline, [ 14 C]lysine, [ 14 C]leucine and [ 14 C]arginine). The upper limits for RNA and protein transfer from Hfr donors is about 1% per recombinant.