Project description:Brucella dynamically engage macrophages while trafficking to an intracellular replicative niche as macrophages, the first line of innate host defense, attempt to eliminate organisms. Brucella melitensis, B. neotomae, and B. ovis are highly homologous, yet exhibit a range of host pathogenicity and specificity. RAW 264.7 macrophages infected with B. melitensis, and B. ovis exhibit divergent patterns of bacterial persistence and clearance; conversely, B. melitensis and B. neotomae exhibit similar patterns of infection. Evaluating early macrophage interaction with Brucella spp. allows discovery of host entry and intracellular translocation mechanisms, rather than bacterial replication. Microarray analysis of macrophage transcript levels following a 4 hr Brucella spp. infection revealed 130 probe sets altered compared to uninfected macrophages; specifically, 72 probe sets were increased and 58 probe sets were decreased with any Brucella spp. Interestingly, much of the inflammatory response was not regulated by the number of Brucella gaining intracellular entry, as macrophage transcript levels were often equivalent among B. melitensis, B. ovis, and B. neotomae infections. An additional 33 probe sets were identified with altered macrophage transcript levels among Brucella spp. infections that may correlate with species specific host defenses and intracellular survival. Gene ontological categorization unveiled genes altered among species are involved in cell growth and maintenance, response to external stimuli, transcription regulation, transporter activity, endopeptidase inhibitor activity and G-protein mediated signaling. Host transcript profiles provide a foundation to understand variations in Brucella spp. infections, while structure of the macrophage response and intracellular niche of Brucella spp. will be revealed through piecewise consideration of host signaling pathways. Keywords: Macrophage, intracellular pathogen, Brucella melitensis, Brucella neotomae, Brucella ovis, inflammatory immune response, species specificity
Project description:To explore the role of Brucella BI-1 in Brucella suis S2, we constructed the Brucella BI-1 deletion mutant strain and its complementary strain. We then determined the effect of Brucella BI-1 deletion on the physiological characteristics of Brucella suis S2 and revealed them via integrated transcriptomic and proteomic analyses. Brucella BI-1 deletion altered the membrane properties of Brucella suis S2 and decreased its resistance to acidic pH, H2O2, polymyxin B, and lincomycin. Additionally, deleting Brucella BI-1 led to defective growth, cell division, and viability in Brucella suis S2. In conclusion, our results revealed that Brucella BI-1 is a bacterial cytoprotective protein involved in membrane homeostasis, cell division, and stress resistance in Brucella suis S2.
Project description:In order to uncover transcriptional changes occurring in Brucella- infected mouse brains that might lead to neurologic complications, we infected susceptible mice intranasally with Brucella and harvested their brains.
Project description:Brucella spp. is an intracellular pathogen in vivo. The intracellular B. melitensis transcriptome was determined by initially enriched and then amplified B. melitensis RNA from total RNA of B. melitensis-infected HeLa cells. Analysis of microarray results identified 161 and 115 genes differentially expressed at 4 and 12 h p.i., respectively. Most of the genes (78%) differentially expressed were down-regulated at the earliest time point, but up-regulated (75%) at 12 h p.i. The analysis of the results indicates that Brucella undergo an adaptation period during the first 4 h p.i. that is overcome by 12 h p.i., permitting Brucella to replicate intracellularly. Specific genes and biological processes identified in this study will further help elucidate how Brucella act during the early infectious process to their eventual benefit and to the detriment of the naïve host. Keywords: Time course study of intracellular B. melitensis gene expression
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:Gene expression analysis of wild-type and STING knock-out mouse bone marrow-derived macrophages (mBMDM) infected with Brucella abortus or transfected with Brucella abortus DNA. Genes whose expression are affected by Brucella abortus in a STING-dependent manner will be identified and signaling pathways regulated by STING will be elucidated.