Small curved Gram-negative bacteria closely related to Wolinella succinogenes, Campylobacter spp., and Acrobacter spp.
The genus Helicobacter currently comprises 23 validly named species. These can be subdivided into the gastric Helicobacter species, which colonize the mucosa of the stomach of their host organisms, and the enterohepatic Helicobacter species, which colonize the gut and/or the liver.
Isolates are characterized biochemically by the presence of urease, catalase, and oxidase activites
Many Helicobacter species can colonize the intestines or biliary tracts of humans and other mammals, where they cause an inflammatory response
H. pylori is the only recognized bacterial carcinogen.
H. pylori are extraordinary bacteria in their ability to colonize the human gastric mucosa, an inherently inhospitable acidic environment, and to persist in this niche for many decades, despite the development of host immune and inflammatory response. Persistent colonization with has been recognized as a significant risk factor for serious gastroduodenal disease.
H. pylori is a genetically diverse species, with strains differing markedly in virulence.
Gastric and duodenal ulcers
Genomes (comparative pathogenomics):
H. acinonychis str. Sheeba, 1553927 bp, NC_008229
H. hepaticus ATCC 51449, 1799146 bp, NC_004917
H. mustelae 12198, 1578097 bp, NC_013949
H. pylori 26695, 1667867 bp, NC_000915
H. pylori G27, 1652982 bp, NC_011333
H. pylori HPAG1, 1596366 bp, NC_008086
H. pylori J99, 1643831 bp, NC_000921
H. pylori P12, 1673813 bp, NC_011498
H. pylori Shi470, 1608548 bp, NC_010698
Eppinger M, et al., 2006. Who ate whom? Adaptive Helicobacter genomic changes that accompanied a host jump from early humans to large felines. PLoS Genet 2(7):e120.
Suerbaum S, et al., 2003. The complete genome sequence of the carcinogenic bacterium Helicobacter hepaticus. Proc. Natl. Acad. Sci. USA. 100(13):7901-7906.
Tomb JF, et al., 1997. The complete genome sequence of the gastric pathogen Helicobacter pylori Nature 388(6642):539-547.
Baltrus DA, et al., 2009. The complete genome sequence of Helicobacter pylori strain G27. J Bacteriol 191(1):447-448.
Oh JD, et al., 2006. The complete genome sequence of a chronic atrophic gastritis Helicobacter pylori strain: evolution during disease progression. Proc Natl Acad Sci USA 103(26):9999-10004.
Alm RA, et al., 1999. Genomic-sequence comparison of two unrelated isolates of the human gastric pathogen Helicobacter pylori Nature 397(6715):176-180.
Fischer W, et al., 2010. 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.
Major virulence factors in Helicobacter:
Type IV secretion system
Type IV secretory protein
Pathogenicity islands in Helicobacter:
Location of virulence-associated genes in H. pylori: