Diversity and phylogeny of the Helicobacter pylori outer membrane protein-encoding gene homC

Cordeiro, Rita; Ménard, Armelle; Breurec, Stéphane; Mégraud, Francis; Oleastro, Mónica

http://hdl.handle.net/10400.18/352

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Abstract(s)

The genetic diversity and evolution of the homC gene was evaluated in a panel of approximately 200 clinical and reference strains, isolated from patients from different geographical origins and presenting different gastric diseases. PCR, sequencing and bioinformatics analyses were used. All the strains tested harboured a complete homC gene at a conserved locus. Phylogenetic reconstruction of homC showed a geographical segregation, with three predominant groups: Western, East Asian/Amerindian and African. A similarity plot analysis suggested a conserved profile of gene segmentation, where three segments were defined. In the first segment (5¢ end extremity), sequences were separated according to the geographical origin of the strain. A higher level of diversity (<50%) was observed in the middle segment, while the third segment (3¢ end extremity) was the most conserved (~90%). In the middle segment, eight allelic variants were identified, with geographic specificity regarding the most prevalent ones. The AI allele was predominant and exclusive of Western strains. The AII allele was predominant in African strains and was the only allele present in the three geographical groups. The AIV allele was predominant in East Asian/ Amerindian strains and was not observed in Western strains. The Western group showed greater molecular distance while the sequences from the East Asian/ Amerindian group were the closest. Overall, the regular presence of homC and its allelic variability suggest that this gene is a good candidate to be part of the pool of H. pylori outer membrane proteins involved in bacterial persistence.