THE PHA GENE CLUSTER OF BRUCELLA ABORTUS INVOLVED IN PH ADAPTATION

LERNER BETIANA; ROSET MARA; CIOCCHINI ANDRES; IANNINO FLORENCIA; IÑON DE IANNINO NORA

PINAMAR

Congreso; FEDERACION IBEROAMERICANA DE BIOLOGIA CELULAR Y MOLECULAR, Y SOCIEDAD ARGENTINA DE INVESTIGACIONES EN BIOQUIMICA Y BIOLOGIA MOLECULAR (SAIB); 2005

SAIB

The operon phaABCDEFG in Sinohizobium meliloti code for a K+secretion system that is involved in the adaptation to pH changesand in symbiosis. In B. abortus a locus highly similar to pha operonof S. meliloti was identified. This cluster of genes is 6 kb and ispredicted to encode six membrane-spanning proteins. In this studya polar mutant in phaA/B was constructed and characterized by invitro and in vivo assays. Growth of the mutant was impaired indefine medium at alkaline pH by concentration of added K+ as lowas 0.04 M. This phenotype was suppressed with 20 mM sodiumacetate added. We studied the multiplication of the Brucella wildtype and the mutant in professional and non-professionalphagocytes. B. abortus 2308 phaA/B mutant showed differencesin the adherence and/or invasiveness in HeLa and J774 cells and lessability to replicate intracellulary during the first hours after infectionin HeLa cells. In mouse model the mutant resulted in a reduction of0.88 and 0.89 Log CFU/spleen at 10 and 30 days post-infectionrespectively. The indexes of competition between both strains were7.47 and 1.88 at 10 and 30 days post-infection respectively. Theseresults suggest that the pha operon is important for the homeostaticcapacity of pH and for K+ resistance via an K+/H+ antiporter andmight be necessary for adaptation to the intracellular lifestyle andvirulence.