Project description:Many pathogenic bacteria use a regulatory process termed Quorum Sensing (QS) to produce and detect small diffusible molecules to synchronize gene expression within a population. In Gram-negative bacteria, the detection and response to these molecules depend on transcriptional regulators belonging to the LuxR family. Such a system have been discovered in the intracellular pathogen Brucella melitensis, a Gram-negative bacteria responsible for brucellosis, a word-wide zoonosis remaining a serious public health concern in endemic countries. Two LuxR-type regulators, VjbR and BabR, have been identified in the genome of this pathogen. The vjbR mutant is highly attenuated in all tested models suggesting a crucial role of QS in the virulence of Brucella. This attenuation is at least due to the involvement of VjbR in the activation of the virB operon coding for a type four secretion system essential for Brucella to reach its intracellular replication compartment. At present, no function has been attributed to BabR. To assess the role of both Brucella QS-regulators, we performed in tandem comparative transcriptomic and proteomic analyses of vjbR and babR mutants. These experiments revealed that 10% of Brucella genome is regulated through those regulators, revealing that QS is a global regulatory system in this intracellular pathogen. The overlapping between BabR and VjbR targets suggest an unexpected cross-talk between these two regulators. Moreover, our results demonstrate that VjbR and BabR regulate many gene and/or proteins involved in stress response, metabolism and virulence. These targets are potentially involved in the adaptation of Brucella to the oxidative, pH and nutritional stresses encountered within the host. These findings highlight the involvement of QS in the virulence of Brucella and led us to suggest that this regulatory system could be implied in the spatial and sequential adaptation of Brucella to the host environment. Keywords: Quorum Sensing, Comparative gene expression, Brucella melitensis
Project description:Hfq is a bacterial Sm-like protein which serves as a post-transcriptional regulator of global gene expression. It has been shown to be involved in a wide range of cellular processes and pathways. To characterize the regulation roles of Hfq in Brucella melitensis, the in vitro hfq induction conditions simulating intracellular environments were firstly defined, and then, the transcriptome of the hfq mutant was compared to that of the wild type strain. Comparative transcriptome analysis showed that a total of 359 genes showed a>2.0-fold change in transcript abundance in Δhfq when compared to that in 16M.
Project description:Quorum sensing system (QS) is a global regulator that regulates gene expression in response to cell density and other environmental factors. Two QS genes have been identified in Brucella, one of which (vjbR) is involved in Brucella intracellular survival and virulence. But the regulation mechanism of Brucella intracellular survival by the vjbR remains unknown.To characterize the regulation roles of vjbR, the in vitro vjbR induction conditions simulating intracellular environments were firstly defined, and then, transcriptome of the vjbR mutant is compared to that of the wild type strain. The vjbR gene was highly activated under acidified nutrition limitation condition. Comparative transcriptome analysis showed that a total of 126 genes were greatly differentially expressed in the vjbR mutant.
Project description:Hfq is a bacterial Sm-like protein which serves as a post-transcriptional regulator of global gene expression. It has been shown to be involved in a wide range of cellular processes and pathways. To characterize the regulation roles of Hfq in Brucella melitensis, the in vitro hfq induction conditions simulating intracellular environments were firstly defined, and then, the transcriptome of the hfq mutant was compared to that of the wild type strain. Comparative transcriptome analysis showed that a total of 359 genes showed a>2.0-fold change in transcript abundance in Δhfq when compared to that in 16M. 2 wild type samples and 2 hfq mutant samples were analyzed.
Project description:Quorum sensing system (QS) is a global regulator that regulates gene expression in response to cell density and other environmental factors. Two QS genes have been identified in Brucella, one of which (vjbR) is involved in Brucella intracellular survival and virulence. But the regulation mechanism of Brucella intracellular survival by the vjbR remains unknown.To characterize the regulation roles of vjbR, the in vitro vjbR induction conditions simulating intracellular environments were firstly defined, and then, transcriptome of the vjbR mutant is compared to that of the wild type strain. The vjbR gene was highly activated under acidified nutrition limitation condition. Comparative transcriptome analysis showed that a total of 126 genes were greatly differentially expressed in the vjbR mutant. 2 wild type samples and 2 vjbR mutant samples were analyzed.
Project description:The four-carbon sugar erythritol is an important component of B. melitensis pathogenesis. To determine the transcriptional response to erythritol, B. melitensis strain 16M was grown in the presence of either glucose or erythritol as a sole carbon source.
