Proteomic and phylogenetic analysis of the outer membrane protein repertoire of gastric Helicobacter species. Proteomic and phylogenetic analysis of the outer membrane protein repertoire of gastric Helicobacter species

Helicobacter pylori is considered as the most important risk factor for gastric malignancies worldwide. Its outer membrane is equipped with a large set of outer membrane proteins (OMPs) and several of these OMPs are involved in colonization of the human gastric mucosa. Besides H. pylori, zoonotic non-H. pylori helicobacters (NHPH) have also been associated with gastric disease in humans. Currently, it is largely unknown which OMPs play a role in their colonization process. Therefore, the OMPs from all known gastric Helicobacter species with fully annotated genome sequences were characterized in the present study. The OMPs from 4 enterohepatic helicobacters, 2 closely-related Campylobacter species and Escherichia coli were included for comparison. All genomes were in silico screened for genes encoding OMPs and the identified OMPs were classified into distinct families based on their sequence homology. Phylogenetic analyses were applied and OMPs with a possible function in colonization or virulence were characterized in more detail. Several well-conserved OMP families were identified, including TonB-dependent receptors, an outer membrane factor, an outer membrane phospholipase and Imp/OstA. Moreover, several OMP families were only detected in Helicobacter and primarily in gastric species. These included SfpA/LpxR, two porin families and a VacA-like cytotoxin. In addition, gastric Helicobacter species harbored proportionally the most OMPs and various species-specific families were found in canine and feline helicobacters. In conclusion, we identified several OMP families that are of interest for future NHPH virulence and colonization studies.