Bacterial adaptation to environmental conditions is essential to ensure maximal fitness in the face of several stresses. In this context, two-component systems (TCSs) represent a predominant signal transduction mechanism, allowing an appropriate response to be mounted when a stimulus is sensed. As facultative intracellular pathogens, Brucella spp. face various environmental conditions, and an adequate response is required for a successful infection process. Recently, bioinformatic analysis of Brucella genomes predicted a set of 15 bona fide TCS pairs, among which some have been previously investigated. In this report, we characterized a new TCS locus called prlS/R, for probable proline sensor-regulator. It encodes a hybrid histidine kinase (PrlS) with an unusual Na(+)/solute symporter N-terminal domain and a transcriptional regulator (belonging to the LuxR family) (PrlR). In vitro, Brucella spp. with a functional PrlR/S system form bacterial aggregates, which seems to be an adaptive response to a hypersaline environment, while a prlS/R mutant does not. We identified ionic strength as a possible signal sensed by this TCS. Finally, this work correlates the absence of a functional PrlR/S system with the lack of hypersaline-induced aggregation in particular marine Brucella spp.
Mirabella, A., Yañez Villanueva, R-M., Delrue, R-M., Uzureau, S., Zygmunt, M. S., Cloeckaert, A., ... Letesson, J-J. (2012). The two-component system PrlS/PrlR of Brucella melitensis is required for persistence in mice and appears to respond to ionic strength. Microbiology, 158(Pt 10), 2642-51. https://doi.org/10.1099/mic.0.060863-0