Introduction of the Streptococcus faecalis transposon Tn 916 into Bacillus thuringiensis subsp. israelensis

Abstract

The conjugative Streptococcus faecalis transposon Tn 916 was introduced into Bacillus thuringiensis subsp. israelensis by filter matings with S. faecalis. B. thuringiensis transconjugants resistant to tetracycline (Tet r) were detected at a frequency of approximately 7.0 × 10 −7 per recipient cell during filter matings, whereas transfer of Tn 916 was not observed in broth matings. The Tet r phenotype in subsp. israelensis was stable in the absence of antibiotic selection. Southern hybridization analysis revealed that Tn 916 had inserted into several different sites on the B. thuringiensis subsp. israelensis chromosome but insertion into plasmid DNA was not observed. Movement of Tn 916 was demonstrated when Tet r B. thuringiensis transconjugants were mated with isogenic recipients. Southern hybridizations, however, showed that the resulting Tet r isolates contained Tn 916 junction fragments that were nearly identical to the donor, suggesting that this movement resulted from transfer of chromosomal DNA from donor to recipient or from a fusion of mating cells, rather than conjugative transposition of the Tn element.