Iron uptake in Brucella melitensis

Brucella is a Gram negative facultative intracellular bacteria causing infectious process both in man and animals. The identification of factors used by the bacteria to colonize its host or to escape its defense mechanisms (virulence factors in a broad sense) is a key step to a better understanding of the pathogenesis of this disease. The strategy is based on the screening of a library of transposon mutants of B. melitensis in order to identify mutants whose survival is altered in in vitro condition which mimic an in vivo environment encountered by the bacteria, low Fe . About twenty mutants were identified with an attenuated phenotype on iron deprived media and are under characterization. Three of these mutants are affected in siderophore assimilation and an other mutant, in intracellular survival. By the characterization of these mutants, iron uptake and its implication in virulence is then studied for Brucella. We have identified in Brucella, a conserved energy dependent ferric iron transport system and its associates ABC transporter specific to Brucella's siderophore. A conserved GTP binding protein until now without known function is implicated in siderophore assimilation by Brucella