Spermine hinders post-conjugational recombination in Escherichia coli K-12.

Treatment of Hfr and F- mixture with spermine during the first minutes of mating decreased the number of viable recombinants and inhibited functional recombinant structure formation in the intragenic cross lacz157Xlaczs. The treatment applied after 15 minutes of mating was ineffective. The decrease of recombination frequency was not caused by any interference in mating union formation. The efficiency of donor DNA transfer in the presence of spermine was increased two-fold. Spermine blocked the formation of S1-nuclease degradable DNA in the post-conjugant recipient cells. It is suggested that spermine probably interferes with the early steps of recombination, most likely by the stabilization of DNA against strand separation.