Conjugative plasmid DNA transfer in Helicobacter pylori mediated by chromosomally encoded relaxase and TraG-like proteins

Abstract

One of the striking characteristics ofHelicobacter pyloriis the extensive genetic diversity among clinical isolates. This diversity has been attributed to an elevated mutation rate, impaired DNA repair, DNA transfer and frequent recombination events. Plasmids have also been identified inH. pyloribut it remained unknown whether conjugation can contribute to DNA transfer between clinical isolates. To examine whetherH. pyloripossesses intrinsic capability for conjugative plasmid transfer, shuttle vectors were introduced intoH. pyloricontaining anoriTsequence of the conjugative IncPαplasmid RP4 but no mobilization (mob) genes. It was shown that these vectors could stably replicate and be mobilized among clinicalH. pyloristrains. It was also demonstrated thattraGand relaxase (rlx) homologues carried on theH. pylorichromosome were important for plasmid transfer. Primer extension studies and mutagenesis further confirmed that the relaxase homologuerlx1inH. pyloriencodes a functional enzyme capable of acting on the RP4oriT. Furthermore, the findings of this study indicate thattraGandrlx1act independently of the previously described type IV secretion systems, including that encoded by thecagpathogenicity island and thecomBtransformation apparatus, in mediating conjugative plasmid DNA transfer betweenH. pyloristrains.