title: Major contribution of the type II beta carbonic anhydrase CanB (Cj0237) to the capnophilic growth phenotype of Campylobacter jejuni.
abstract: Campylobacter jejuni, the leading cause of human bacterial gastroenteritis, requires low environmental oxygen and high carbon dioxide for optimum growth, but the molecular basis for the carbon dioxide requirement is unclear. One factor may be inefficient conversion of gaseous CO2 to bicarbonate, the required substrate of various carboxylases. Two putative carbonic anhydrases (CAs) are encoded in the genome of C. jejuni strain NCTC 11168 (Cj0229 and Cj0237). Here, we show that the deletion of the cj0237 (canB) gene alone prevents growth in complex media at low (1% v/v) CO2 and significantly reduces the growth rate at high (5% v/v) CO2. In minimal media incubated under high CO2, the canB mutant grew on L-aspartate but not on the key C3 compounds L-serine, pyruvate and L-lactate, showing that CanB is crucial in bicarbonate provision for pyruvate carboxylase-mediated oxaloacetate synthesis. Nevertheless, purified CanB (a dimeric, anion and acetazolamide sensitive, zinc-containing type II beta-class enzyme) hydrates CO2 actively only above pH 8 and with a high Km (∼ 34 mM). At typical cytoplasmic pH values and low CO2, these kinetic properties might limit intracellular bicarbonate availability. Taken together, our data suggest CanB is a major contributor to the capnophilic growth phenotype of C. jejuni.
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Halah
authors.initials: H
authors.lastname: Al-Haideri
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: Michael A
authors.initials: MA
authors.lastname: White
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Kelly
mesh_terms: D001224:Aspartic Acid / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism; D016123:Campylobacter jejuni / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D024402:Carbonic Anhydrase II / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D019344:Lactic Acid / Q000378:metabolism; D062907:Oxaloacetic Acid / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010641:Phenotype; D011766:Pyruvate Carboxylase / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism; D012694:Serine / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D003470:Culture Media; D002245:Carbon Dioxide; D062907:Oxaloacetic Acid; D001224:Aspartic Acid; D019344:Lactic Acid; D012694:Serine; D019289:Pyruvic Acid; D024402:Carbonic Anhydrase II; D011766:Pyruvate Carboxylase; D010100:Oxygen