Functional comparison of conjugative transposons Tn916 and Tn925.

During interspecies matings between Bacillus subtilis and Bacillus thuringiensis subsp. israelensis, transfer of conjugative transposon Tn916 was detected at a frequency of 1.1 x 10(-4) transconjugants per donor. Tn916-dependent transfer of plasmids pC194 and pE194 was detected at frequencies of 1.4 x 10(-5) and 3.2 x 10(-7) transconjugants per donor, respectively. Similar frequencies were obtained during parallel matings with otherwise isogenic strains that contain Tn925 instead of Tn916. Tn916- or Tn925-dependent transfer of plasmids pC194 or pUB110 from the recipient to the donor (retrotransfer) was not observed during inter- or intraspecies matings. Transposon-mediated plasmid transfer by Tn916 and Tn925 is a Rec independent event. Thus, the data from studies in which otherwise isogenic donor and recipient strains were used indicated that Tn916 and Tn925 are, from a functional point of view, much more similar than previously suggested.