Beschreibung:
<jats:title>Abstract</jats:title>
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<jats:title>Background</jats:title>
<jats:p>In prokaryotes, the ureases are multi-subunit, nickel-containing enzymes that catalyze the hydrolysis of urea to carbon dioxide and ammonia. The <jats:italic>Brucella</jats:italic> genomes contain two urease operons designated as <jats:italic>ure</jats:italic> 1 and <jats:italic>ure</jats:italic> 2. We investigated the role of the two <jats:italic>Brucella suis</jats:italic> urease operons on the infection, intracellular persistence, growth, and resistance to low-pH killing.</jats:p>
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<jats:title>Results</jats:title>
<jats:p>The deduced amino acid sequence of urease-α subunits of operons-1 and -2 exhibited substantial identity with the structural ureases of alpha- and beta-proteobacteria, Gram-positive and Gram-negative bacteria, fungi, and higher plants. Four <jats:italic>ure</jats:italic> deficient strains were generated by deleting one or more of the genes encoding urease subunits of <jats:italic>B. suis</jats:italic> strain 1330 by allelic exchange: strain 1330Δ<jats:italic>ure</jats:italic> 1K (generated by deleting <jats:italic>ureD</jats:italic> and <jats:italic>ureA</jats:italic> in <jats:italic>ure</jats:italic> 1 operon), strain 1330Δ<jats:italic>ure</jats:italic> 2K (<jats:italic>ureB</jats:italic> and <jats:italic>ureC</jats:italic> in <jats:italic>ure</jats:italic> 2 operon), strain 1330Δ<jats:italic>ure</jats:italic> 2C (<jats:italic>ureA</jats:italic>, <jats:italic>ureB</jats:italic>, and <jats:italic>ureC</jats:italic> in <jats:italic>ure</jats:italic> 2 operon), and strain 1330Δ<jats:italic>ure</jats:italic> 1KΔ<jats:italic>ure</jats:italic> 2C (<jats:italic>ureD</jats:italic> and <jats:italic>ureA</jats:italic> in <jats:italic>ure</jats:italic> 1 operon and <jats:italic>ureA</jats:italic>, <jats:italic>ureB</jats:italic>, and <jats:italic>ureC</jats:italic> in <jats:italic>ure</jats:italic> 2 operon). When grown in urease test broth, strains 1330, 1330Δ<jats:italic>ure</jats:italic> 2K and 1330Δ<jats:italic>ure</jats:italic> 2C displayed maximal urease enzyme activity within 24 hours, whereas, strains 1330Δ<jats:italic>ure</jats:italic> 1K and 1330Δ<jats:italic>ure</jats:italic> 1KΔ<jats:italic>ure</jats:italic> 2C exhibited zero urease activity even 96 h after inoculation. Strains 1330Δ<jats:italic>ure</jats:italic> 1K and 1330Δ<jats:italic>ure</jats:italic> 1KΔ<jats:italic>ure</jats:italic> 2C exhibited slower growth rates in tryptic soy broth relative to the wild type strain 1330. When the BALB/c mice were infected intraperitoneally with the strains, six weeks after inoculation, the splenic recovery of the <jats:italic>ure</jats:italic> deficient strains did not differ from the wild type. In contrast, when the mice were inoculated by gavage, one week after inoculation, strain 1330Δ<jats:italic>ure</jats:italic> 1KΔ<jats:italic>ure</jats:italic> 2C was cleared from livers and spleens while the wild type strain 1330 was still present. All <jats:italic>B. suis</jats:italic> strains were killed when they were incubated <jats:italic>in-vitro</jats:italic> at pH 2.0. When the strains were incubated at pH 2.0 supplemented with 10 mM urea, strain 1330Δ<jats:italic>ure</jats:italic> 1K was completely killed, strain 1330Δ<jats:italic>ure</jats:italic> 2C was partially killed, but strains 1330 and 1330Δ<jats:italic>ure</jats:italic> 2K were not killed.</jats:p>
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<jats:title>Conclusion</jats:title>
<jats:p>These findings suggest that the <jats:italic>ure</jats:italic> 1 operon is necessary for optimal growth in culture, urease activity, resistance against low-pH killing, and <jats:italic>in vivo</jats:italic> persistence of <jats:italic>B. suis</jats:italic> when inoculated by gavage. The <jats:italic>ure</jats:italic> 2 operon apparently enhances the resistance to low-pH killing <jats:italic>in-vitro</jats:italic>.</jats:p>
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