Mechanism of Helicobacter pylori DNA exchange and microcin delivery
Zusammenfassung der Projektergebnisse
Many Helicobacter pylori strains (Hp) carry cryptic plasmids of different size and gene content, the function of which is not well understood. A subgroup of these plasmids exhibits a mobilization region, (e.g. pHel4, pHel12), but no cognate type IV secretion system (T4SS) for conjugative transfer. However, distinct H. pylori strains (e.g. strain P12 bearing plasmid pHel12) can harbour up to four T4SSs in their genome (cag-T4SS, comB, Tfs3, Tfs4). Here, we show that such indigenous plasmids can be efficiently transferred between H. pylori strains, as long as the recipient strains carry already a related plasmid. Using a marker-free contra-selectable gene deletion procedure (rpsL contraselection method), we constructed H. pylori P12 mutant strains with a consecutive deletion of each individual T4SS, finally generating a P12 mutant strain with no single T4SS (P12∆T4SS). This procedure identified the comB T4SS as the major mediator of plasmid DNA transfer between H. pylori. Altogether our data indicate that H. pylori uses at least three different pathways of plasmid DNA transfer. These include (i) the comB-dependent DNaseI-sensitive uptake of extracellular plasmid via natural transformation, (ii) a novel identified comB-dependent, but DNaseI- resistant plasmid mobilization procedure reliant on a functional plasmid-encoded (mobA) relaxase gene, and (iii) a novel T4SS-independent, DNaseI-resistant, conjugation-like mechanism. However, independent of the mode of periplasmic delivery (transformation, mobilization, conjugation-like transfer), successful plasmid transfer between H. pylori is strictly dependent on the inner membrane channel protein ComE3. Furthermore, we determined the complete genome sequence of the H. pylori duodenal ulcer strain P12. The P12 genome contains three plasticity zones (PZ1-PZ3), two of which encode type IV secretion systems and have typical features of genomic islands. One of these T4SS, which we termed Tfs4, was a previously unknown T4SS, which was only found as a complete system in H. pylori P12. The function of Tfs4 is to secrete H. pylori plasmid DNA to make it available for natural transformation. In addition, we demonstrate for the first time that the genomic island PZ1 is capable of self-excision and horizontal transfer by a conjugative process.
Projektbezogene Publikationen (Auswahl)
- Outer membrane protein expression profile in Helicobacter pylori clinical isolates. Infect Immun. 9:3782-90 (2009)
Odenbreit S, Swoboda K, Barwig I, Ruhl S, Borén T, Koletzko S, Haas R
- Virulence Mechanisms and Persistence Strategies of the Human Gastric Pathogen Helicobacter pylori. Curr Top Microbiol Immunol. 337:129-71 (2009)
Fischer, W., Prassl, S., Haas, R.
- Biochemical and functional characterization of Helicobacter pylori vesicles. Mol Microbiol. 77(6):1539-55 (2010)
Olofsson A, Vallström A, Petzold K, Tegtmeyer N, Schleucher J, Carlsson S, Haas R, Backert S, Wai SN, Gröbner G, Arnqvist A
- Strain-specific genes of Helicobacter pylori: genome evolution driven by a novel type IV secretion system and genomic island transfer. Nucleic Acids Res 38(18):6089-6101 (2010)
Fischer W, Windhager L, Rohrer S, Zeiller M, Karnholz A, Hoffmann R, Zimmer R, Haas R
