Helicobacter pylori
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Classification
Higher order taxa
Domain: Bacteria ; Phylum: Proteobacteria; Class: Epsilon Proteobacteria; Order: Campylobacterales; Family: Helicobacteraceae [Others may be used. Use Tree of Life link to find]
Species
Helicobacter pylori
Description and significance
Helicobacter pylori is a spiral-shaped gram-negative bacterium that infects the stomach. It can cause damage to stomach and duodenal tissue, which causes ulcers, gastritis (inflammation of the gastric mucosa of the stomach), and in some cases cancer. Robin Warren and Barry Marshall discovered the bacterium in 1982 and they were the first to culture it successfully. They purposed that it was H. pylori that caused stomach ulcers but this was not recognized at that time because people debated over whether the stomach environment would allow bacteria to survive. To prove their point, Marshall drank a Petri dish of H. pylori and he developed gastritis. The bacteria was isolated from the lining of his stomach and this proved three out of four of Koch’s postulates (which establish the relationship between a microbe and a disease). Further investigations went on to determine the relationship between H. pylori and ulcers and numerous studies around the world confirmed this. The National Institute of Health confirmed that gastric ulcers are caused by H. Pylori in 1994.
Genome structure
Helicobacter pylori contains one circular chromosome that carries 1,667,867 base pairs. It has about 1590 coding regions. The genome has been sequenced and it is being studied and compared to find out more about its lifestyle and pathogenicity.
Cell structure and metabolism
Helicobacter pylori is a slow growing helical-shaped gram-negative bacterium with flagella. It’s a microaerophilic bacterium, meaning that it requires oxygen at lower levels compared to the oxygen level in the atmosphere. It can use hydrogenase to obtain energy. Hydrogenase produces energy by oxidizing molecular hydrogen that is produced by the bacteria present in the intestine.
Ecology
Helicobacter pylori lives in the acidic environment of the stomach and duodenum where many other microorganisms would not survive. The flagella is used to drill through the mucus gel layer of the stomach. H. Pylori has been found to live inside the mucus gel layer, above epithelial cells, and inside vacuoles in the epithelial cells. Adhesins allow it to adhere to epithelial cells by attaching to membrane-bound lipids and carbohydrates. Other animals such as dogs, cats, and ferrets have also been infected by H. pylori. In the humans, infection leads to gastritis which if left untreated leads to the formation of ulcers. In the long run this can possibly cause gastric cancer.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Current Research
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