Rank: Species
Lineage: Bacteria;delta/epsilon subdivisions;Epsilonproteobacteria;Campylobacterales;Helicobacteraceae;Helicobacter;Helicobacter pylori
Description: It was only recently discovered (1983) by two Australians (Warren and Marshall) that this organism was associated with peptic ulcers. It is one of the most common chronic infectious organisms, and is found in half the world's population. This organism attacks the gastric epithilial surface, resulting in chronic gastritis, and can cause more severe diseases including those that lead to gastric carcinomas and lymphomas, peptic ulcers, and severe diarrhea. It is an extracellular pathogen that persists in the gastric environment, which has a very low pH, by production of the urease enzyme, which converts urea to ammonia and carbon dioxide, a process which can counteract the acidic environment by production of a base. The chromosome contains genes which encode the urease gene cluster, various cytotoxins, and the cag pathogenicity island. The toxins include cytolethal distending toxin, vacuolating cytotoxin (VacA) that induces host epithelial cell apopoptosis (cell death), and the cytotoxin associated antigen (CagA) which results in alteration to the host cell signalling pathways. The CagA protein is translocated into host cells by a type IV secretion system encoded by the cag pathogenicity island. The cell also expresses numerous adhesins that are responsible for attachment, including those for binding to the Lewis group antigens. A number of genes contain homopolymeric tracts of repeated nucleotides for phase variation and antigenic diversity.
Reference Material:
https://www.ncbi.nlm.nih.gov/genome/?term=Helicobacter%20pylori
