RECOMBINANT-DNA TRANSFER TO ESCHERICHIA-COLI OF HUMAN FECAL ORIGIN IN-VITRO AND IN DIGESTIVE-TRACT OF GNOTOBIOTIC MICE

The role of helper elements in the mobilisation of pBR recombinant pla smids (tra(-), mob(-), oriT(+) and tra(-), mob(-), oriT(-)) from genet ically engineered Escherichia coli K12 strains to other K12 strains an d to wild-type E. coli strains of human faecal origin was examined. Tr ansfer experiments were done in the digestive tract of axenic (germ fr ee) and gnotobiotic mice, associated with human faecal flora, HFF. The kinetics of implantation of donors, recipients and transconjugants we re determined. Mobilisation of oriT(+) pBR-type plasmids, by trans-com plementation with the products of tra and mob genes was obtained with E. coli K12, in the digestive tract of axenic mice and the resulting t ransconjugants became established together with the recipient and dono r strains. Such mobilisation was only observed sporadically with one E . coli of human origin in axenic mice, but did not occur in gnotobioti c HFF mice. The E. coli strains of human origin were able to promote t ransfer of an oriT(-) pBR-type plasmid in vitro but not in axenic or g notobiotic mice. Transconjugants of wild-type strains obtained in in v itro mating experiments and inoculated into gnotobiotic HFF mice were eliminated as rapidly as the recombinant K12 strains. This work indica tes that greater than or equal to 50% of wild-type E. coli strains wer e able to promote transfer of pBR oriT(-) plasmids in vitro.