Phenotypes controlled by the Brucella abortus two component system BvrR/BvrS differ in their dependence on the phosphorylation of the response regulator BvrR

Brucella abortus is a zoonotic pathogen whose ability to survive intracellularly at the endoplasmic reticulum is essential for its virulence. The two-component system BvrR/BvrS is essential for intracellular survival due to the transcriptional control of the type IV secretion system VirB and its transcriptional regulator VjbR. In addition, this system is a master regulator of several traits including membrane conformation by controlling proteins such as Omp25.  To understand the regulatory strategies used by BvrR we generated dominant positive and negative versions of this response regulator which, in addition to the wild type version, were introduced in a BvrR- background. We then characterized BvrRS-controlled phenotypes and the expression of proteins controlled by the system. We found two regulatory patterns exerted by BvrR. The first pattern was represented by resistance to polymyxin and expression of Omp25 (membrane conformation) which were restored to normal levels by the dominant positive and the wild type version, but not the dominant negative version, of BvrR. The second pattern was represented by intracellular survival and expression of VjbR and VirB (virulence) which were, again, fully complemented by wild type and the dominant versions of BvrR but, significantly restored by complementation with the dominant negative version of the response regulator. These results suggested a differential binding of unphosphorylated BvrR with promoters of the genes it controls. We confirmed this hypothesis by showing that the dominant negative version of BvrR was not able to interact with the promoter of omp25 but was able to interact with the promoter of vjbR. Furthermore, a global transcriptional analysis indicated that some genes respond to the presence of the dominant negative version of BvrR.  Thus, BvrR possesses diverse strategies to exert transcriptional control on the genes it regulates and as consequence on the phenotypes controlled by this response regulator.

Here, we include the raw count data (rawcounts.txt) for all analyzed samples,  as well as the experimental designed used to perform the statistical results (target.txt).