Project description:We used B. melitensis M5-90 wild type to construct gene-deleted strains of B. melitensis ∆per, RAW264.7 cells infected with B. melitensis M5-90 and B. melitensis M5-90 ∆per for 4h, respectively. miRNA microarray and mRNA array experiments were performed, qRT-PCR validation for miRNAs and mRNAs. We performed a joint analysis of differentially expressed miRNAs and mRNAs, and proved that the target gene of miRNA-146b is Tbc1d14. It further confirmed that miR-146b targeting tbc1d14 regulates brucella-mediated autophagy of RAW264.7 cells. Finally, the molecular mechanism of tbc1d14 influencing brucella-mediated autophagy of RAW264.7 cells was preliminarily revealed by DGE sequencing.
Project description:We used B. melitensis M5-90 wild type to construct gene-deleted strains of B. melitensis ∆per, RAW264.7 cells infected with B. melitensis M5-90 and B. melitensis M5-90 ∆per for 4h, respectively. miRNA microarray and mRNA array experiments were performed, qRT-PCR validation for miRNAs and mRNAs. We performed a joint analysis of differentially expressed miRNAs and mRNAs, and proved that the target gene of miRNA-146b is Tbc1d14. It further confirmed that miR-146b targeting tbc1d14 regulates brucella-mediated autophagy of RAW264.7 cells. Finally, the molecular mechanism of tbc1d14 influencing brucella-mediated autophagy of RAW264.7 cells was preliminarily revealed by DGE sequencing.
Project description:Brucella spp. are gram-negative, facultative intracellular pathogens that cause brucellosis in humans and animals. Iron is an essential element required for all organisms. Iron response regulator (Irr) is a crucial transcriptional regulator and can affect the growth and iron uptake of Brucella. The growth rate of Brucella melitensis M5-90 irr mutant was significantly lower than that of B. melitensis M5-90 under normal or iron-sufficient conditions, however, the growth rate of the B. melitensis M5-90 irr mutant was significantly higher than that of B. melitensis M5-90 under iron-limited conditions. In addition, irr mutation significantly reduced iron uptake under iron-limited conditions. Currently, bhuA (a heme transporter), bhuQ (heme utilization oxygenase Q), and RirA (iron-responsive regulator) have been identified as iron metabolism genes and are regulated by the Irr protein. These results suggest that the Irr protein has multiple target genes in the Brucella genome that are involved in iron metabolism. Therefore, a combination of RNA-seq and Dap-seq was used to investigate the other iron metabolism genes that are also regulated by the Irr protein in Brucella. A total of seven genes were identified as target genes for Irr in this study and the expression levels of these seven genes were similar in both the RNA-seq and qRT-PCR results. Furthermore, the DNA bases C and G and amino acids asparagine, arginine, histidine, and serine were predicted as predominant docking sites for DNA and Irr using the HDOCK server. The electrophoretic mobility shift assay confirmed that six out of the seven genes, namely rirA (BME_RS13665), membrane protein (BME_RS01725), hypothetical protein (BME_RS09560), Iron transporter (BME_RS14525), cation-transporting P-type ATPase (BME_RS10660), and 2Fe-2S binding protein (BME_RS13655), interact with the Irr protein. In summary, our results identified six genes regulated by the Irr protein that may participate in iron metabolism. In addition, from the RNA-seq results, the mutation of irr resulted in the down/upregulation of many genes that are associated with the bacterial secretion system, lipopolysaccharides, and flagellar assembly, and these three components are the main virulence factors for Brucella. Collectively, these results provide valuable insights for the exploration of Brucella iron metabolism and its effects on virulence.
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: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. Experiment Overall Design: Murine J774.A1 macrophage cells were infected with B. melitensis strain 16M at a MOI of 200:1. Brucella cultures derived from different Brucella colonies were used to infect different groups of macrophage cells to reflect independent infections. Following 4 h incubation, the cells were washed with PBS and treated with 50 ug/ml gentamicin to kill extracellular Brucella. At 0 h (no Brucella infection), 4 h, 24 h, and 48 h post-infection, cells were individually collected, and total RNA was isolated. The Affymetrix mouse GeneChip 430 2.0 array was used for microarray hybridization. Microarray intensity data were obtained by using Affymetrix GCOS software and further analyzed by GeneSpring and other software programs.
Project description:Brucella melitensis and Brucella canis differ by ~75 genes yet B. melitensis is highly virulent for humans while B. canis is considered rarely pathogenic. No identified bacterial factors or mechanisms account for this difference in virulence. To identify functional differences of these two bacteria, gene transcription was examined during infection of murine macrophages and compared to bacteria grown in broth. Our analysis identified transcriptional differences in macrophage infection between B. melitensis and B. canis genes involved in iron transport. Increased transcription of the TonB, enterobactin, and ferric anguibactin transport systems were observed in B. canis but not B. melitensis during infection of macrophages. Therefore, iron appears as an important requirement during the first 24h of infection by B. canis but not for B. melitensis and provides strategies for controlling these pathogens. Comparison of total bacterial RNA from Brucella melitensis infected murine macrophages to broth grown bacteria
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 melitensis and Brucella canis differ by ~75 genes yet B. melitensis is highly virulent for humans while B. canis is considered rarely pathogenic. No identified bacterial factors or mechanisms account for this difference in virulence. To identify functional differences of these two bacteria, gene transcription was examined during infection of murine macrophages and compared to bacteria grown in broth. Our analysis identified transcriptional differences in macrophage infection between B. melitensis and B. canis genes involved in iron transport. Increased transcription of the TonB, enterobactin, and ferric anguibactin transport systems were observed in B. canis but not B. melitensis during infection of macrophages. Therefore, iron appears as an important requirement during the first 24h of infection by B. canis but not for B. melitensis and provides strategies for controlling these pathogens. Comparison of total bacterial RNA from Brucella canis infected murine macrophages to broth grown bacteria
Project description:Brucella melitensis and Brucella canis differ by ~75 genes yet B. melitensis is highly virulent for humans while B. canis is considered rarely pathogenic. No identified bacterial factors or mechanisms account for this difference in virulence. To identify functional differences of these two bacteria, gene transcription was examined during infection of murine macrophages and compared to bacteria grown in broth. Our analysis identified transcriptional differences in macrophage infection between B. melitensis and B. canis genes involved in iron transport. Increased transcription of the TonB, enterobactin, and ferric anguibactin transport systems were observed in B. canis but not B. melitensis during infection of macrophages. Therefore, iron appears as an important requirement during the first 24h of infection by B. canis but not for B. melitensis and provides strategies for controlling these pathogens. comparison of total bacterial RNA from Brucella canis infected murine macrophages and broth grown bacteria