Rapid conjugative mobilization of a 100 kb segment of Bacillus subtilis chromosomal DNA is mediated by a helper plasmid with no ability for self-0transfer

Background: The conjugative plasmid, pLS20, isolated from Bacillus subtilis natto, has an outstanding capacity for rapid self-transfer. In addition, it can function as a helper plasmid, mediating the mobilization of an independently replicating co-resident plasmid. Results: In this study, the oriT sequence of pLS20cat (oriT(LS20)) was eliminated to obtain the plasmid, pLS20cat Delta oriT. This resulted in the complete loss of the conjugative transfer of the plasmid but still allowed it to mobilize a co-resident mobilizable plasmid. Moreover, pLS20cat Delta oriT was able to mobilize longer DNA segments, up to 113 kb of chromosomal DNA containing oriT(LS20), after mixing the liquid cultures of the donor and recipient for only 15 min. Conclusions: The chromosomal DNA mobilization mediated by pLS20cat Delta oriT will allow us to develop a novel genetic tool for the rapid, easy, and repetitive mobilization of longer DNA segments into a recipient chromosome.