title: Characterization of the urease operon of Brucella abortus and assessment of its role in virulence of the bacterium.
abstract: Most members of the genus Brucella show strong urease activity. However, the role of this enzyme in the pathogenesis of Brucella infections is poorly understood. We isolated several Tn5 insertion mutants deficient in urease activity from Brucella abortus strain 2308. The mutations of most of these mutants mapped to a 5.7-kbp DNA region essential for urease activity. Sequencing of this region, designated ure1, revealed the presence of seven open reading frames corresponding to the urease structural proteins (UreA, UreB, and UreC) and the accessory proteins (UreD, UreE, UreF, and UreG). In addition to the urease genes, another gene (cobT) was identified, and inactivation of this gene affected urease activity in Brucella. Subsequent analysis of the previously described sequences of the genomes of Brucella spp. revealed the presence of a second urease cluster, ure2, in all them. The ure2 locus was apparently inactive in B. abortus 2308. Urease-deficient mutants were used to evaluate the role of urease in Brucella pathogenesis. The urease-producing strains were found to be resistant in vitro to strong acid conditions in the presence of urea, while urease-negative mutants were susceptible to acid treatment. Similarly, the urease-negative mutants were killed more efficiently than the urease-producing strains during transit through the stomach. These results suggested that urease protects brucellae during their passage through the stomach when the bacteria are acquired by the oral route, which is the major route of infection in human brucellosis.
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria, C/Cardenal Herrera Oria s/n, 39011 Santander, Spain.
authors.forename: Félix J
authors.initials: FJ
authors.lastname: Sangari
authors.forename: Asunción
authors.initials: A
authors.lastname: Seoane
authors.forename: María Cruz
authors.initials: MC
authors.lastname: Rodríguez
authors.forename: Jesús
authors.initials: J
authors.lastname: Agüero
authors.forename: Juan M
authors.initials: JM
authors.lastname: García Lobo
mesh_terms: D000143:Acids / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002003:Brucella abortus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity*; D002006:Brucellosis / Q000382:microbiology*; D015169:Colony Count, Microbial; D019295:Computational Biology; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004195:Disease Models, Animal; D005260:Female; D017353:Gene Deletion; D051379:Mice; D008807:Mice, Inbred BALB C; D050296:Microbial Viability; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016366:Open Reading Frames; D009876:Operon; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013270:Stomach / Q000382:microbiology; D014508:Urea / Q000378:metabolism; D014510:Urease / Q000235:genetics* / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000143:Acids; D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D037521:Virulence Factors; D014508:Urea; D014510:Urease