TAXONOMY: Bacteria -> Proteobacteria -> delta/epsilon subdivisions -> Epsilonproteobacteria -> Campylobacterales -> Helicobacteraceae -> Helicobacter
Helicobacter is a genus of Gram-negative bacteria possessing a characteristic helical shape. They were initially considered to be members of the Campylobacter genus, but in 1989 Goodwin et al. published sufficient reasons to justify his new genus name of Helicobacter. The Helicobacter genus contains about 35 species.Some species have been found living in the lining of the upper gastrointestinal tract, as well as the liver of mammals and some birds. The most widely known species of the genus is H. pylori, which infects up to 50% of the human population. Some strains of this bacterium are pathogenic to humans, as they are strongly associated with peptic ulcers, chronic gastritis, duodenitis, and stomach cancer. It also serves as the type species of the genus. Cells may be curved, spiral, or fusiform rods, 0.2–1.2 × 1.5–10.0 µm. Spiral cells may be tightly or loosely wound depending on the species, and on the age and condition of the culture examined. Cells in old cultures or those exposed to air become coccoid. Ultrastructural studies show that periplasmic fibers may be observed on the cell surface of a few taxa and an electrondense glycocalyx- or capsule-like layer has been observed on the cell surface of some species. Nonsporeforming. Gram negative. Motile with a rapid corkscrew- or slower wave-like motion due to flagellar activity. Multiple sheathed flagella are seen in most species, frequently with a bipolar distribution. Typical cell morphologies of various Helicobacter species are shown in Figs. BXII.ε.5 and BXII.ε.6. The mol% G + C of the DNA is: 24–48. Type species: Helicobacter pylori.
Helicobacter species are able to thrive in the very acidic mammalian stomach by producing large quantities of the enzyme urease, which locally raises the pH from about 2 to a more biocompatible range of 6 to 7. Bacteria belonging to this genus are usually susceptible to antibiotics such as penicillin, are microaerophilic (optimal oxygen concentration between 5 and 14%) capnophiles, and are fast-moving with their flagella.
This genus contains microbial species that can reside in the human gastrointestinal tract. [PMC 4262072] Recent studies showed that eradication of H. pylori with antibiotics increases l-DOPA bioavailability in Parkinson patients, with a single antibiotic dose improving motor symptoms for 3 months or more. H. pylori may affect l-DOPA bioavailability by disrupting absorption at the duodenal mucosa, by producing ROS that inactivate the drug, and via direct metabolism of l-DOPA. However, recent work suggests that H. pylori also compromises l-DOPA bioavailability through direct binding.