Differential Expression of Iron Acquisition Genes by Brucella melitensis and Brucella canis During Macrophage Infection (part 2)

Brucella melitensis and Brucella canis differ by ~75 genes yet B. melitensis is highly virulent for humans while B. canis is considered rarely pathogenic. No identified bacterial factors or mechanisms account for this difference in virulence. To identify functional differences of these two bacteria, gene transcription was examined during infection of murine macrophages and compared to bacteria grown in broth. Our analysis identified transcriptional differences in macrophage infection between B. melitensis and B. canis genes involved in iron transport. Increased transcription of the TonB, enterobactin, and ferric anguibactin transport systems were observed in B. canis but not B. melitensis during infection of macrophages. Therefore, iron appears as an important requirement during the first 24h of infection by B. canis but not for B. melitensis and provides strategies for controlling these pathogens. Comparison of total bacterial RNA from Brucella canis infected murine macrophages at 5 and 24h