Conditions for conjugative transposon transfer in Lactococcus lactis

Three different techniques for bacterial mating were applied to wild type and culture collection strains of Lactococcus lactis harbouring transposons: direct plate conjugation, filter mating and mating on milk agar. Efficiencies and frequencies of transfer were compared. Transconjugants were characterized by marker properties and molecular assays. Transposon-coded Suc+ Nis+ phenotype as well as Suc+ Bac+ Nis- phenotype were transferred with frequencies ranging between 10-9 and 10-6. Milk agar plate mating was the best technique for obtaining gene transfer events involving wild type lactococci.