Factors affecting transfer frequency of pAM beta 1 from Streptococcus faecalis to Lactobacillus plantarum.

Conjugal transfer of streptococcal plasmid pAM beta 1 to Lactobacillus plantarum by a filter mating method was examined under various conditions. The transfer frequency depended greatly on the type, pore size, and side (front or back) of the membrane filter. The passage of sterilized water through the membrane under reduced pressure after donor and recipient cells were trapped on it increased the transfer frequency about 10-fold.