Gene transfer from engineered Lactococcus lactis strains to Enterococcus faecalis in the digestive tract of gnotobiotic mice.

The introduction of genetically modified organisms into food products requires an evaluation of the behaviour and the dissemination of foreign genes of such organisms among the human intestinal microflora. The conjugal transfer, both in vitro and in vivo (in mice digestive tract) of DNA from Lactococcus lactis donor strains to an Enterococcus faecalis strain isolated from human faecal flora was studied. We followed the transfer of (1) the self-transmissible plasmid pIL205; (2) two non-self-transmissible but mobilizable plasmids, pIL252 and pIL253; (3) one plasmid, pMS1.5B, integrated into the chromosome of L. lactis. In vitro, the transfer frequency of pIL205 (expressed as the number of transconjugants per donor cell) was 9.6 x 10(-4); mobilization of one of the non-self-transmissible plasmids, pIL253, was observed (4.9 x 10(-7)). In vivo, only transfer of pIL205 and pIL253 occurred, but the frequency was not determined. The transfer of pMS1.5B was not detected in vitro or in vivo.