Brucella abortus ure2 region contains an acid-activated urea transporter and a nickel transport system.
BACKGROUND
Urease is a virulence factor that plays a role in the resistance of Brucella to low pH conditions, both in vivo and in vitro. Brucella contains two separate urease gene clusters, ure1 and ure2. Although only ure1 codes for an active urease, ure2 is also transcribed, but its contribution to Brucella biology is unknown.


RESULTS
Re-examination of the ure2 locus showed that the operon includes five genes downstream of ureABCEFGDT that are orthologs to a nikKMLQO cluster encoding an ECF-type transport system for nickel. ureT and nikO mutants were constructed and analyzed for urease activity and acid resistance. A non-polar ureT mutant was unaffected in urease activity at neutral pH but showed a significantly decreased activity at acidic pH. It also showed a decreased survival rate to pH 2 at low concentration of urea when compared to the wild type. The nikO mutant had decreased urease activity and acid resistance at all urea concentrations tested, and this phenotype could be reverted by the addition of nickel to the growth medium.


CONCLUSIONS
Based on these results, we concluded that the operon ure2 codes for an acid-activated urea transporter and a nickel transporter necessary for the maximal activity of the urease whose structural subunits are encoded exclusively by the genes in the ure1 operon.
Sangari
Félix J
FJ
Departamento de Biología Molecular, Universidad de Cantabria, Instituto de Biomedicina y Biotecnología de Cantabria, UC-CSIC-IDICAN, Santander, Spain. sangarif@unican.es
Cayón
Ana M
AM
Seoane
Asunción
A
García-Lobo
Juan M
JM
D000143:Acids / Q000378:metabolism* / Q000633:toxicity; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000633:toxicity; D001426:Bacterial Proteins / Q000235:genetics*; D002003:Brucella abortus / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D050296:Microbial Viability; D005810:Multigene Family; D009532:Nickel / Q000378:metabolism*; D009876:Operon; D013312:Stress, Physiological; D015533:Transcriptional Activation; D014510:Urease / Q000378:metabolism; D000096982:Urea Transporters
D000143:Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D009532:Nickel; D014510:Urease; D000096982:Urea Transporters