Helicobacter: Difference between revisions

Revision as of 14:11, 14 August 2006

A Microbial Biorealm page on the Helicobacter

NCBI:
Taxonomy
Genome: H. hepaticus

H. pylori 26695

H. pylori J99

Helicobacter pylori. From Professor D. J. Kelly.

Classification

Higher order taxa:

Bacteria; Proteobacteria; delta/epsilon subdivisions; Epsilonproteobacteria; Campylobacterales; Helicobacteraceae

Species:

Candidatus H. bovis, Candidatus H.cebus, Candidatus H. suis, H. acinonychis, H. apodemus, H. aurati, H. bilis, H. bizzozeronii, H. canadensis, H. canis sp., H. cetorum, H. cholecystus, H. cinaedi, H. felis, H. fennelliae, H. ganmani, H. heilmannii sp., H. hepaticus sp., H. marmotae, H. mesocricetorum, H. muricola, H. muridarum, H. mustelae, H. pametensis, H. pullorum sp., H. pylori sp., H.rappini, H. rodentium, H. salomonis, H. suncus, H. trogontum, H. tursiopsae, H. typhlonius, H. winghamensis, H. sp.

Description and Significance

Helicobacter is a Gram-negative, slow-growing organism. H. pylori has importance as a common human pathogen.

Genome Structure

Helicobacter pylori is composed of a single circular chromosome with 1,667,867 base pairs, containing about 1590 coding regions (TIGR, 2004).

Cell Structure and Metabolism

Helicobacter is a spiral shaped organism with flagella. It has a potent multisubunit urease enzyme that enables it to survive in acidic pH conditions and colonize the gastric environment (TIGR, 2004). H. pylori utilizes the enzyme urease to convert urea into bicarbonate and ammonia to combat the low acidity of the stomach. The mixing of the two extreme pH levels creates a neutralized protective cloud around the H. pylori, allowing it to survive in the stomach (Helicobacter Foundation, 2004).

Ecology

Helicobacter is able to live in the acidity of the stomach and duodenum, living on the mucus lining of the stomach, causing several health problems for the host (Helicobacter Foundation, 2004). Helicobacter can also be seen in animals such as cheetahs, dogs, cats, and ferrets (J. Solnick et al. 2004).

Pathology

A duodenal ulcer caused by H. pylori. From the Helicobacter Foundation.

A gastric ulcer caused by H. pylori. From the Helicobacter Foundation.

Until the discovery of Helicobacter in 1982, ulcers were thought to be caused by stress. Now it is known that ulcers, in addition to gastritis, are caused by a bacterial infection of H. pylori. Though relatively easy to treat with antibiotics, H. pylori can be a risk factor for gastric cancer if it becomes a long-term infection (D. J. Kelly, 2004).

The body's natural defenses cannot combat H. pylori because white and killer T cells cannot easily get through the stomach lining. The defense cells eventually die, spilling their superoxide radicals on stomach lining cells, on which H. pylori can feed (Helicobacter Foundation, 2004).