Characterization of the Urease Operon of Brucella abortus and Assessment of Its Role in Virulence of the Bacterium

• Published in: Infection and Immunity Vol. 75; no. 2; pp. 774 - 780
• Main Authors: Sangari, Félix J, Seoane, Asunción, Rodríguez, María Cruz, Agüero, Jesús, García Lobo, Juan M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01.02.2007
• Subjects: Acids - pharmacology; Animals; Anti-Bacterial Agents - pharmacology; Bacteria; Bacteriology; Biological and medical sciences; Brucella abortus; Brucella abortus - drug effects; Brucella abortus - enzymology; Brucella abortus - genetics; Brucella abortus - pathogenicity; Brucellosis - microbiology; Colony Count, Microbial; Computational Biology; Disease Models, Animal; DNA Transposable Elements; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Female; Fundamental and applied biological sciences. Psychology; Gene Deletion; Mice; Mice, Inbred BALB C; Microbial Viability; Microbiology; Miscellaneous; Molecular Pathogenesis; Molecular Sequence Data; Mutagenesis, Insertional; Open Reading Frames; Operon; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Stomach - microbiology; Urea - metabolism; Urease - genetics; Urease - metabolism; Virulence Factors - genetics; Virulence Factors - metabolism; Brucellaceae; Microbiology; Enzyme; Operon; Virulence; Bacteria; Hydrolases; Urease; Brucella abortus; Immunity; Brucella melitensis
• DOI: 10.1128/IAI.01244-06
• ISSN: 0019-9567

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.