title: Is Helicobacter pylori a true microaerophile?
abstract: BACKGROUND
  There is no general consensus about the specific oxygen and carbon dioxide requirements of the human pathogen Helicobacter pylori. This bacterium is considered a microaerophile and consequently, it is grown under atmospheres at oxygen tensions 5-19% and carbon dioxide tensions 5-10%, both for clinical and basic and applied research purposes. The current study compared the growth of H. pylori in vitro, under various gas atmospheres, and determined some specific changes in the physiology of bacteria grown under different oxygen partial pressures.
  
  
  METHODS
  Measurements of bacterial growth under various conditions were carried out employing classical solid and liquid culture techniques. Enzymatic activities were measured using spectrophotometric assays.
  
  
  RESULTS
  H. pylori and all the other Helicobacter spp. tested had an absolute requirement for elevated carbon dioxide concentrations in the growth atmosphere. In contrast with other Helicobacter spp., H. pylori can tolerate elevated oxygen tensions when grown at high bacterial concentrations. Under 5% CO(2), the bacterium showed similar growth in liquid cultures under oxygen tensions from microaerobic (< 5%) to fully aerobic (21%) at cell densities higher than 5 x 10(5) cfu/ml for media supplemented with horse serum and 5 x 10(7) cfu/ml for media supplemented with beta-cyclodextrin. Evidence that changes occurred in the physiology of H. pylori was obtained by comparing the activities of ferredoxin:NADH (nicotinamide adenine dinucleotide) oxidoreductases of bacteria grown under microaerobic and aerobic atmospheres.
  
  
  CONCLUSIONS
  H. pylori is a capnophile able to grow equally well in vitro under microaerobic or aerobic conditions at high bacterial concentrations, and behaved like oxygen-sensitive microaerophiles at low cell densities. Some characteristics of H. pylori cells grown in vitro under microaerobic conditions appeared to mimic better the physiology of organisms grown in their natural niche in the human stomach.
authors.affiliation: Unité de Pathogénie Bactérienne des Muqueuses, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris cedex 15, France.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bury-Moné
authors.forename: Nadeem O
authors.initials: NO
authors.lastname: Kaakoush
authors.forename: Corinne
authors.initials: C
authors.lastname: Asencio
authors.forename: Francis
authors.initials: F
authors.lastname: Mégraud
authors.forename: Marie
authors.initials: M
authors.lastname: Thibonnier
authors.forename: Hilde
authors.initials: H
authors.lastname: De Reuse
authors.forename: George L
authors.initials: GL
authors.lastname: Mendz
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000032:analysis; D002245:Carbon Dioxide; D003470:Culture Media / Q000737:chemistry; D005288:Ferredoxins / Q000032:analysis; D016480:Helicobacter pylori / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D010100:Oxygen; D010313:Partial Pressure; D044967:Serum; D047392:beta-Cyclodextrins
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D005288:Ferredoxins; D047392:beta-Cyclodextrins; D002245:Carbon Dioxide; D010100:Oxygen