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interpreted the data and wrote the manuscript. Both authors read and approved the final manuscript.”
“Background Urease catalyzes the chemical hydrolysis of the urea molecule into CO2 and ammonia. These equilibrate in water causing a rise of the pH of the medium. Accordingly, bacterial ureases serve two main purposes: to neutralize acidic conditions, and to provide a source of assimilable nitrogen. Pathogenic bacteria exploit urease activity in different ways along the infectious Baf-A1 cell line process. In Brucella spp, as well as in Helicobacter pylori, Klebsiella and Yersinia, urease allows bacteria to survive the acidic conditions encountered in the stomach during the gastrointestinal infection [1–5]. The role of bacterial ureases in infectious disease has been recently reviewed . Ureases are complex enzymes generally composed of three structural subunits (UreABC). To assemble a functional urease, the cooperation of several accessory proteins is required
(UreEFGD) and, as a consequence, large gene clusters are needed to encode for functional ureases. Brucella contains two urease operons, both located in chromosome I. The Brucella ure1 operon contains the genes ureDABCEFG, and the Brucella ure2 locus shows the structure ureABCEFGDT . The last gene of ure2, ureT, encodes a putative urea transporter homologous to Yut from Yersinia pseudotuberculosis . Most Brucella species show a strong urease activity, derived from ure1 but not from ure2, and this activity is responsible for the ability of Brucella to survive stomachal transit and to establish a systemic infection [1, 2]. B. ovis is not able to infect the host by the gastrointestinal route, a fact that has been linked to its lack of urease activity . Furthermore, purification and characterization of urease from B. suis showed the presence of urease subunits from ure1 but not from ure2 . Strikingly, ure2 genes are transcribed in vivo [1, 2], suggesting that they play a role in Brucella.