Helicobacter pylori, a Gastric Pathogen causing Persistent Infection

Helicobactor pylori, a gastric pathogen from ｔｈｅ δ, ε subdivision of proteobacteria, is a microaerophilic, Gram-negative, flagellate, spiral bacter ium. It shares these properties with the related food-borne pathogen Campylobacter jejuni. The genomes of H. pylori 26695 and C. jejuni NCTC11168 are similar in size and predicted to encode 1,590 and 1,654 proteins, respectively. Despite the close phylogenetic relationship of H. pylori and C.jejuni, only 55.4% of H. pylori genes have orthologs in C.jejuni and strong similarities between them are mainly confined to housekeeping functions. H. pylori but not C. jejimi, has a unique ammoniaproducing system to neutralize gastric acid and pathogenic factors such as VacA and CagA. In addition, it acquired hypervariable properties in the outer membrance proteins and Lewis-antigens of lipopolysaccharide to colonize a wide range of the human host. Thus selective pressures have driven profound evolutionary changes to create specific pathogens appropriate to their niches, from a relatively close common ancestor.

Campylobacter jejuni

ammonia production

outer membrane

protein

Lewis antigen