Superinfection with R Factors by Transduction in Escherichia coli and Salmonella typhimurium

Tsutomu Watanabe, Sachiko Sakaizumi, Chizuko Furuse
1968 Journal of Bacteriology  
Superinfection immunity is found in the conjugal transfer of R factors between two fi+ R factors and between two ft-R factors (fi = fertility inhibition), as we reported previously. In contrast, no reduction in the frequencies of transduction of an fi+ R factor 222 was caused by the presence offi+ R factors in the recipients in transduction systems with phage Plkc in Escherichia coli K-12 and with phage P22 in Salmonella typhimurium LT-2. The absence of superinfection immunity in transduction
more » ... y be due to the difference in the route of entry of the R factor. The frequencies of transduction of an fi+ R factor were reduced, although slightly, by the presence of fi-R factors in the recipients. This reduction is probably due to hostcontrolled restriction of the entering fi+ R factor by the ft-R factors in the recipients, since transduction of an fi+ R factor by the transducing phage propagated on the strain carrying both fi+ and fl-R factors was not reduced by the presence of homologous fi-R factors in the recipients. The fi+ R factor 222, when transduced to the recipient strains carrying other R factors, recombined genetically at high frequencies with these resident R factors, regardless of their fi type. R factors frequently recombined after transductional superinfection. These results and their possible mechanisms will be discussed. MATERIALS AND METHODS Bacterial strainis. Two substrains of E. coli K-12 were used: CSH-2 (F-, methionine-requiring) and W677/PTS (F-, threonine-, leucine-, proline-, and thiamine-requiring, mannitol-, xylose-, maltose-, galactose-, and lactose-nonfermenting, and resistant to phage T6 and high concentrations of streptomycin).
doi:10.1128/jb.96.5.1796-1802.1968 fatcat:f5x6qwpaxfadxfthzmujm6pxfm