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:Considering the role of PTMs(2-hydroxyisobutyrylation, succinylation, crotonylation, acetylation, and malonylation) in various biological processes of Brucella virulence and survival, we propose that the virulence of Brucella is associated with the PTMs of proteins. Taken together, this study provides the first global survey of PTMs in Brucella. This is a prospective starting point for further functional analysis of PTMs during the survival of Brucella in hosts, interpretation of the function of Brucella proteins, and elucidation of the pathogenic mechanism of Brucella.
Project description:Facultative intracellular Brucella infect and survive inside macrophages, and the outcome of macrophage-Brucella interaction is a basis for establishment of a chronic Brucella infection. The majority of Brucella are killed at the early infection stage. A subpopulation of virulent Brucella strains is instead trafficked to an intracellular replicative phagosome, and are resistant to further attack and begin to multiply dramatically. Virulent Brucella also inhibit macrophage apoptosis that in turn favors pathogen survival and replication. We used the Affymetrix mouse GeneChip 430 2.0 array to analyze mouse macrophage gene expression profiles during the time course of virulent B. melitensis strain 16M infection. Keywords: time course
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: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.
Project description:Histone-like nucleoid structuring (H-NS) and H-NS-like proteins serve as global gene silencers and work with antagonistic transcriptional activators (counter- silencers) to properly coordinate the expression of virulence genes in pathogenic bacteria. In Brucella, MucR has been proposed as a novel H-NS-like gene silencer, but direct experimental evidence is lacking. Here, we show that MucR serves as an H-NS-like silencer of the Brucella abortus genes encoding the polar autotransporter adhesins BtaE and BmaC, the c-di-GMP-specific phosphodiesterase BpdB, and the quorum-sensing regulator BabR. We also demonstrate that the MarR-type transcriptional activator MdrA can displace MucR from the btaE promoter, supporting the existence of MucR counter- silencers in Brucella. Moreover, our chromatin immunoprecipitation (ChIP)-seq analysis identified 546 MucR enrichment peaks along the genome, including in the promoters of the genes encoding the Type IV secretion machinery and effectors and the quorum- sensing regulator VjbR. Importantly, MucR ChIP-seq peaks overlap with the previously described binding sites for the transcriptional activators VjbR, BvrR, and CtrA suggesting that these regulators serve as MucR counter-silencers and work in concert with MucR to coordinate virulence gene expression in Brucella. In addition, using chromosome conformation capture (Hi-C), we show that like H-NS in Escherichia coli, MucR alters the global structure of the Brucella nucleoid. Finally, a copy of the E. coli hns rescues the distinctive growth defect and elevated btaE expression of a B. abortus mucR mutant. Together, these findings solidify the role of MucR as a novel type of H-NS-like protein and suggest that MucR’s gene-silencing properties play a key role in virulence in Brucella.