Project description:The virB operon, encoding a Type IV secretion system (T4SS), is essential for intracellular survival and persistent infection of Brucella spp. To better understand the role of the T4SS in evading host defense mechanisms and establishing chronic infection, we compared transcriptional profiles of the host response to infection with wild type Brucella strains and strains that fail to express the virB genes. Analysis of host gene expression profiles three days after inoculation with wild type Brucella strains revealed an inflammatory response dominated by interferon-induced genes. This analysis found that not only the type II but also type I interferon pathway was elicited by Brucella infection. Real time RT-PCR showed that a group of genes from these pathways was induced by day 3 post-infection and declined to baseline levels by day 7. In contrast, neither of the two virB mutant strains elicited expression of interferon-induced genes, demonstrating that the T4SS was required to trigger an inflammatory response early during infection. Keywords: analysis of transcriptional responses induced by infection
Project description:The virB operon, encoding a Type IV secretion system (T4SS), is essential for intracellular survival and persistent infection of Brucella spp. To better understand the role of the T4SS in evading host defense mechanisms and establishing chronic infection, we compared transcriptional profiles of the host response to infection with wild type Brucella strains and strains that fail to express the virB genes. Analysis of host gene expression profiles three days after inoculation with wild type Brucella strains revealed an inflammatory response dominated by interferon-induced genes. This analysis found that not only the type II but also type I interferon pathway was elicited by Brucella infection. Real time RT-PCR showed that a group of genes from these pathways was induced by day 3 post-infection and declined to baseline levels by day 7. In contrast, neither of the two virB mutant strains elicited expression of interferon-induced genes, demonstrating that the T4SS was required to trigger an inflammatory response early during infection. Experiment Overall Design: We performed microarray-based expression analyses of splenocytes from mice infected with two virulent strains (B. abortus 2308 and B. melitensis 16M), and two different B. abortus virB mutants, whose virB operon was either disrupted (BA41) or completely deleted (ADH4.2), to better understand the contribution of the T4SS in establishing infection of the reticuloendothelial system. 3 days after infection of mice, spleens were excised for RNA extraction. For each bacterial strain, RNA from 5 mice was pooled and reverse transcribed for hybridization to an array. Each experiment was performed in duplicate.
Project description:Brucella, a notorious intracellular pathogen, causes chronic infections in many mammals, including humans. The twin-arginine translocation (Tat) pathway transports folded proteins across the cytoplasmic membrane; protein substrates translocated by Brucella include ABC transporters, oxidoreductases, and cell envelope biosynthesis proteins. Previously, we showed that a Tat mutant of Brucella melitensis M28 exhibits reduced survival within murine macrophages. In this study, we compared the host responses elicited by wild-type M28 and its Tat-mutant strains ex vivo. We utilized label-free quantitative proteomics to assess proteomic changes in RAW264.7 macrophages after infection with M28 and its Tat mutants.
Project description:Wild-type Brucella ovis ATCC 25840 requires the addition of 5% CO2 to the atmosphere to grow on either nutrient agar plates or in liquid broth culture. The goal of this study was to measure the transcriptional response of two Brucella ovis strains under high (5%) and low (0.04%) CO2. The two strains assayed were 1) wild-type and 2) a spontaneous mutant that can be cultivated in standard atmospheric levels of CO2 (~0.04%). Wild-type B. ovis harbors a single nucleotide insertion at the 3' end of a beta carbonic anhydrase gene, bcaA, which renders it non-functional. The spontaneous mutant lost this nucleotide insertion, which restored the consensus reading frame and results in a functional BcaA protein.
Project description:We focused on whether transposon mutagenesis in Brucella abortus could induce difference in the trascriptional responses of RAW 264.7 cell infection model compared to the wild strain infected RAW 264.7 cells. The function of genes in Brucella abortus was analyzed through the identified differences in gene expression between RAW 264.7 cell infected with wild and mutant strains.
Project description:We focused on whether transposon mutagenesis in Brucella abortus could induce difference in the trascriptional responses of RAW 264.7 cell infection model compared to the wild strain infected RAW 264.7 cells. The function of genes in Brucella abortus was analyzed through the identified differences in gene expression between RAW 264.7 cell infected with wild and mutant strains. We analyzed altered transcription in RAW 264.7 cells at 0, 6, 12, and 24 h following the infection with 10 MOI of Brucella abortus wild and mutant strains.
Project description:Investigation of whole genome gene expression level changes in a B. suis 1330 regA mutant, compared to the wild-type strain. The two-component system RegBA of Brucella suis plays a central role in the control of respiratory systems adapted to oxygen deficiency. The mutant strain is affected in long-term persistence in vitro (this study) and in chronic infection in vivo (Abdou, E et al. 2013, Infect.Immun. 81: 2053-61). Using an original “in vitro model of persistence”, we compare large-scale transcriptome of the wild-type and ∆regA strains to identify the RegA-regulon potentially involved in the set-up of the persistence state.
Project description:In this study the transcription profile of bovine trophoblastic cells infected with Brucella samples was evaluated. Chorioallantoic membrane (CAM) explants inoculated with wild type (strain 2308), and to compare with the transcription profile of trophoblastic cells infected with mutant strains lacking virB2 or btpB.ΔvirB2 or ΔbtpB by microarray analysis at 4 hours post infection. Genes with significant variation in levels of transcripts (fold change > 2 and P < 0.05) were functionally classified, and transcripts related to defense and inflammation were assessed by quantitative real time RT-PCR.
Project description:Brucella abortus (B. abortus), an intracellular bacterium, is the causative agent of Brucellosis. This organism invades into macrophages and then survives through its abilities to modulate host cells functions. The biggest problem caused by B. abortus is that it prevents macrophage elimination and makes it difficult to remove B. abortus from the host body. Therefore, it is essential to identify the bacterial genes involved in virulence factor as a first step to understanding the bacterial pathogenicity and controlling Brucellosis. To identify these genes, B. abortus mutant strains were generated using transposon mutagenesis and transcriptomic profile during macrophage infection were analyzed. The gene expression level was analyzed using total RNA obtained from THP-1 cells infected with B. abortus wild type and mutant strains and cellular immunity during the infections were compared to wild type infected cell to identify the role of genes in B. abortus pathogenicity. Transcriptomic profiling showed that two mutant strains having disrupted genes related to 4-hydrobenzoate 3-monooxygenase (PHBH) of C1 strain and heme exporter protein cytochrome C (CcmC) of C10 strain, induced suppression of cytokine expression during infection in human macrophages. Conversely, two other mutant strains of exopolyphosphatase (PPX)of C27 and Peptidase M24 of C32 induced activation of cytokine expression in the THP-1 macrophage cells.
Project description:Recent murine studies have demonstrated that the role of response regulator 09 (RR09) of S. pneumoniae in virulence varies between strains. In the present study, we used a murine pneumonia model of infection to assess the virulence of a TIGR4 rr09-mutant, and found that TIGR4Δrr09 was attenuated after intranasal infection. Further, we investigated the in vitro transcriptional changes in pneumococcal rr09 mutants of two strains, D39 and TIGR4, by microarray analysis. The transcriptional profiles of the rr09 mutants in both strains displayed clear differences compared to their parental wild-type. In D39Δrr09 but not TIGR4Δrr09, genes involved in competence (e.g. comAB) were upregulated. In TIGR4, genes located on the rlrA pathogenicity islet, absent in the D39 genome, appeared to be regulated by RR09. Furthermore, several phosphotransferase systems (PTSs), believed to be involved in sugar uptake (e.g., sp0060-sp0066), were strongly downregulated in D39Δrr09, while not regulated by RR09 in TIGR4. To address the role of one of these PTS in virulence, D39Δsp0063 was constructed and tested in a murine infection model. No difference in virulence compared to the wild-type was found, indicating that downregulation of this gene alone is not the cause of the avirulent phenotype of D39Δrr09. Finally, expression of rr09 and three of our identified RR09 targets were assessed during infection in mice. This in vivo experiment confirmed differences in expression between TIGR4 wild-type and rr09-mutant, as well as between wild-type D39 and TIGR4. In conclusion, our results indicate strain-specific regulation of pneumococcal gene expression by RR09. Keywords: genetic modification