FIG 8.

Model showing the activation of the BvrR/VjbR/VirB virulence circuit at late stages of B. abortus infection. After replication at the ER, B. abortus reaches an aBCV. There, BvrS senses environmental cues such as an acidic pH, triggering its autophosphorylation, and activates, in turn, the regulator protein BvrR. This transcriptional regulator then binds to promoters such as PvjbR and PvirB, enhancing their expression. The type IV secretion system component VirB promotes the exit of the bacterium from its host cell, whereas VjbR induces changes at the membrane that increase the interaction of the bacteria with the host cell in subsequent infection cycles. Plasma membrane (PM).