Helicobacter pylori
A Microbial Biorealm page on the genus Helicobacter pylori
Classification
Higher order taxa
Bacteria (Domain); Proteobacteria (Phylum); Epsilon Proteobacteria (Class); Campylobacterales (Order); Helicobacteraceae (Family); Helicobacter (Genus)
Species
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NCBI: Taxonomy |
Helicobacter pylori
Description and significance
Helicobacter pylori is a Gram negative organism that has a 'helical' shaped body with 6-8 flagella at one end. H. pylori is found in a very acidic environment, a pH of 2.0 or less. It is commonly found inside the lining of the stomach and duodenum. H. pylori can cause peptic ulcers and gastritis that can lead to gastric cancer and gastric MALT lymphoma (mucosa-associated lyphoid tissue).
It was first observed in 19th century that curved bacteria were living in the lining of the stomach, but growing and isolating the bacteria was neglected. H. pylori was discovered by Drs. Robin Warren and Barry Marshall in 1983 that this organism was related to peptic ulcers. They were able to culture the bacteria from the stomach, and conclude that H. pylori was the bacteria that caused peptic ulcers and gastritis.
Helicobacter pylori was initially named Campylobacter pylordis because under the microscopy, it showed similar appearances with the campylobacter, but after DNA sequencing, H.pylori was separated into its own genus Helicobacter in 1989. The Helicobacter reflects to the appearances of the organism, helical in vivo, but often rodlike in vitro.
Genome structure
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
The genome of Helicobacter pylori is circular and contains 1,667,867 base pairs, which 300 bp encodes for membrane proteins, and 1590 bp are predicted coding sequences. The chromosome of the organism contains genes that encodes the urease gene cluster, cytotoxins in the membrane, and the cag pathogenicity island. In 1989, CagA gene was found and identified as the marker strain of the risk of peptic ulcers and gastric cancer. The CagA pathogenicity island recognizes the type IV secretion system, which CagA proteins are moved to the host cells.
The DNA content of H. pylori has GC range of 35-38% which catergorized itself to the Campylobacter species. However, the comparisons of the 16S ribosomal RNA showed that H. pylori was different from Campylobacter but similar to Wolinella succinogenes. which its GC range was 42-49%. H. pylori was placed into its own genus, Helicobacter. after the analysis of the ultrastructure, fatty acid composition and biochemical tests which proved different for H. pylori and W. succinogenes
The analysis of H. pylori sequences specifies the diversity and the development of the organism. H. pylori sequences shows that the recombination and the clone between the strain linkage is uncertain, and the recombination is based on the repetitive DNA sequences that permits the high frequency deletion and duplication of the DNA. The genome contains sequences that encodes for the membrane proteins. For example, the F1F0 ATP synthase complex, various oxidoreductases such as cytochrome o, and some transporters. Sequences show that H. pylori obtains a “well developed systems for motility, for scavenging iron, and for DNA restriction and modification.” [3] Helicobacter pylori are capable to uptake DNA from other H. pylori. Due to the uncertainty of the strain linkages, recombination occurs because of the repetitive DNA squences, which allows high frequency deletion and duplication and mismatch inbetween the strands. Lack of mismatch repairing can increase in frequency of random variation but it can also convert the gene which can bring down the diversity of the organism. [1]
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
[1] Blaser, Martin J and Atherton, John C."Helicobacter pylori persistence: biology and disease". J Clin Invest. 2004 February 1; 113(3): 321–333.
Megraud, F. "Taxonomy and Biology of Helicobacter pylori- a comment". "Helicobacter pylori, Gastritis and Peptic Ulcer". Springer-Verlag Berlin Heidelberg 1990
Marshall, Barry J, McCallum, Richard W and Guerrant, Richard L. "Helicobacter pylori in peptic ulceration and gastritis." Blackwell Scientific Publications 1991.
[2] NCBI Entrez Genome Project
[3] Tomb JF, White O, Kerlavage AR, Clayton RA, Sutton GG, Fleischmann RD, Ketchum KA, Klenk HP, Gill S, Dougherty BA, Nelson K, Quackenbush J, Zhou L, Kirkness EF, Peterson S, Loftus B, Richardson D, Dodson R, Khalak HG, Glodek A, McKenney K, Fitzegerald LM, Lee N, Adams MD, Hickey EK, Berg DE, Gocayne JD, Utterback TR, Peterson JD, Kelley JM, Cotton MD, Weidman JM, Fujii C, Bowman C, Watthey L, Wallin E, Hayes WS, Borodovsky M, Karp PD, Smith HO, Fraser CM, Venter JC. "The complete genome sequence of the gastric pathogen Helicobacter pylori." Nature 1997. 388(6642): 515-6
Edited by Katherine Park student of Rachel Larsen and Kit Pogliano
