RNA-seq reveals the critical role of CspA in regulating Brucella melitensis metabolism and virulence

Brucella melitensis is a facultative intracellular bacterium that replicates within macrophages. The ability of Brucella to survive and multiply in the hostile environment of host macrophages is essential for its virulence. The cold shock protein CspA plays an important role in the virulence of B. melitensis . To analyze the genes regulated by CspA, the whole transcriptomes of B. melitensis NIΔ cspA and its parental wild-type strain, B. melitensis NI, were sequenced and analyzed using the Solexa/Illumina sequencing platform. A total of 446 differentially expressed genes were identified, including 324 up-regulated and 122 down-regulated genes. Numerous genes identified are involved in amino acid, fatty acid, nitrogen, and energy metabolism. Interestingly, all genes involved in the type IV secretion system and LuxR-type regulatory protein VjbR were significantly down-regulated in NIΔ cspA . In addition, an effector translocation assay confirmed that the function of T4SS in NIΔ cspA is influenced by deletion of the cspA gene. These results revealed the differential phenomena associated with virulence and metabolism in NIΔ cspA and NI, providing important information for understanding detailed CspA-regulated interaction networks and Brucella pathogenesis.