The PrlS/PrlR two component signal transduction system (TCS) is highly conserved in sequence and genomic organization in Brucella species, but its function remains completely unknown. TCS regulate genetic expression in response to external or internal environmental signals. In this work PrlS/PrlR mutants were characterized with results suggesting that wt B. melitensis produces aggregates at high osmolarity, contrary to the mutants of the bacterial pathogen Brucella melitensis. Interestingly it could be observed that the matrix of this aggregates contain EPS and that PrlR regulates positively the synthesis and production of EPS. We further investigated the role of prlR on membrane structures such as the flagellum and outer membrane proteins, by studying the regulation of the pfliF promoter in the mutants. Our results suggest that prlR controls both the flagellar system and the regulation of OMPs. B. melitensis mutated for prlR is less virulent compared to the wt suggesting that PrlR may play an important role in virulence. Preliminary transcriptomic comparative analysis of the mRNA profiles of mutant and wild type prlR strains suggests that PrlR regulates approximately 6.41 % of the B. melitensis genome.