Transcriptional regulator GntR of Brucella abortus regulates cytotoxicity, induces the secretion of inflammatory cytokines and affects expression of the type IV secretion system and quorum sensing system in macrophages

2017 ◽  
Vol 33 (3) ◽  
Author(s):  
Zhiqiang Li ◽  
Shuli Wang ◽  
Hui Zhang ◽  
Jinliang Zhang ◽  
Li Xi ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Inflammatory Cytokines ◽  
Brucella Abortus ◽  
Transcriptional Regulator ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Sensing System ◽  
Type Iv ◽  
Quorum Sensing System

scholarly journals Putative Quorum-Sensing Regulator BlxR of Brucella melitensis Regulates Virulence Factors Including the Type IV Secretion System and Flagella

2008 ◽  
Vol 190 (9) ◽  
pp. 3274-3282 ◽  
Author(s):  
Amy A. Rambow-Larsen ◽  
Gireesh Rajashekara ◽  
Erik Petersen ◽  
Gary Splitter
Keyword(s):  
Quorum Sensing ◽  
Virulence Factors ◽  
Brucella Melitensis ◽  
Regulatory Protein ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Deletion Strain ◽  
Type Iv Secretion System ◽  
Type Iv ◽  
Systemic Spread

ABSTRACT Brucella melitensis is an intracellular pathogen that establishes a replicative niche within macrophages. While the intracellular lifestyle of Brucella is poorly understood and few virulence factors have been identified, components of a quorum-sensing pathway in Brucella have recently been identified. The LuxR-type regulatory protein, VjbR, and an N-acylhomoserine lactone signaling molecule are both involved in regulating expression of the virB-encoded type IV secretion system. We have identified a second LuxR-type regulatory protein (BlxR) in Brucella. Microarray analysis of a blxR mutant suggests that BlxR regulates the expression of a number of genes, including those encoding the type IV secretion system and flagella. Confirming these results, deletion of blxR in B. melitensis reduced the transcriptional activities of promoters for the virB operon, flagellar genes, and another putative virulence factor gene, bopA. Furthermore, our data suggested that both BlxR and VjbR are positively autoregulated and cross-regulate the expression of each other. The blxR deletion strain exhibited reduced growth in macrophages, similar to that observed for a vjbR deletion strain. However, unlike the vjbR deletion, the blxR deletion did not fully attenuate virulence in mice. More strikingly, bioluminescent imaging revealed that dissemination of the blxR mutant was similar to that of wild-type B. melitensis, while the vjbR mutant was defective for systemic spread in IRF-1−/− mice, suggesting that these regulators are not functionally redundant but that they converge in a common pathway regulating bacterial processes.

scholarly journals A quorum-sensing regulator controls expression of both the type IV secretion system and the flagellar apparatus of Brucella melitensis

2005 ◽  
Vol 7 (8) ◽  
pp. 1151-1161 ◽  
Author(s):  
Rose-May Delrue ◽  
Chantal Deschamps ◽  
Sandrine Leonard ◽  
Caroline Nijskens ◽  
Isabelle Danese ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Brucella Melitensis ◽  
Flagellar Apparatus ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Type Iv

scholarly journals Quorum-Sensing and BvrR/BvrS Regulation, the Type IV Secretion System, Cyclic Glucans, and BacA in the Virulence of Brucella ovis: Similarities to and Differences from Smooth Brucellae

2012 ◽  
Vol 80 (5) ◽  
pp. 1783-1793 ◽  
Author(s):  
Ana I. Martín-Martín ◽  
Pilar Sancho ◽  
María Jesús de Miguel ◽  
Luis Fernández-Lago ◽  
Nieves Vizcaíno
Keyword(s):  
Quorum Sensing ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Multiplication Rate ◽  
Content Type ◽  
Murine Macrophages ◽  
Brucella Ovis ◽  
Type Iv

ABSTRACTBrucella ovisis a rough bacterium—lacking O-polysaccharide chains in the lipopolysaccharide—that is virulent in its natural host and whose virulence mechanisms remain almost unexplored. In a search for additional traits that distinguishB. ovisfrom smoothBrucella, which require O-polysaccharide chains for virulence, we have analyzed the significance inB. ovisof the main virulence factors described for smoothBrucella. Attempts to obtain strains of virulentB. ovisstrain PA that are mutated in the BvrR/BvrS two-component regulatory system were unsuccessful, suggesting the requirement of that system forin vitrosurvival, while the inactivation ofbacA—in contrast to the results seen with smoothBrucella—did not affect splenic colonization in mice or behavior in J774.A1 murine macrophages. Defects in the synthesis of cyclic ß-1,2 glucans reduced the uptake ofB. ovisPA in macrophages and, although the intracellular multiplication rate was unaffected, led to attenuation in mice. Growth of strains with mutations in the type IV secretion system (encoded by thevirBoperon) and the quorum-sensing-related regulator VjbR was severely attenuated in the mouse model, and although the mutant strains internalized like the parental strain in J774.A1 murine macrophages, they were impaired for intracellular replication. As described forB. melitensis, VjbR regulates the transcription of thevirBoperon positively, and theN-dodecanoyl-dl-homoserine lactone (C12-HSL) autoinducer abrogates this effect. In contrast, no apparent VjbR-mediated regulation of thefliFflagellar gene was observed inB. ovis, probably due to the two deletions detected upstream offliF. These results, together with others reported in the text, point to similarities between rough virulentB. ovisand smoothBrucellaspecies as regards virulence but also reveal distinctive traits that could be related to the particular pathogenicity and host tropism characteristics ofB. ovis.

Comparative proteome analysis of Brucella abortus 2308 and its virB type IV secretion system mutant reveals new T4SS-related candidate proteins

2011 ◽  
Vol 74 (12) ◽  
pp. 2959-2971 ◽  
Author(s):  
Vladimir Paredes-Cervantes ◽  
Raúl Flores-Mejía ◽  
Martha C. Moreno-Lafont ◽  
Humberto Lanz-Mendoza ◽  
Ángel T. Tello-López ◽  
...  
Keyword(s):  
Brucella Abortus ◽  
Proteome Analysis ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Type Iv

scholarly journals Postreplication Roles of theBrucellaVirB Type IV Secretion System Uncovered via Conditional Expression of the VirB11 ATPase

mBio ◽  
2016 ◽  
Vol 7 (6) ◽  
Author(s):  
Erin P. Smith ◽  
Cheryl N. Miller ◽  
Robert Child ◽  
Jennifer A. Cundiff ◽  
Jean Celli
Keyword(s):  
Brucella Abortus ◽  
Secretion System ◽  
Effector Proteins ◽  
Type Iv Secretion ◽  
Host Cells ◽  
Type Iv Secretion System ◽  
Secretion Systems ◽  
Type Iv ◽  
Conditional Expression ◽  
Bacterial Replication

ABSTRACTBrucella abortus, the bacterial agent of the worldwide zoonosis brucellosis, primarily infects host phagocytes, where it undergoes an intracellular cycle within a dedicated membrane-bound vacuole, theBrucella-containing vacuole (BCV). Initially of endosomal origin (eBCV), BCVs are remodeled into replication-permissive organelles (rBCV) derived from the host endoplasmic reticulum, a process that requires modulation of host secretory functions via delivery of effector proteins by theBrucellaVirB type IV secretion system (T4SS). Following replication, rBCVs are converted into autophagic vacuoles (aBCVs) that facilitate bacterial egress and subsequent infections, arguing that the bacterium sequentially manipulates multiple cellular pathways to complete its cycle. The VirB T4SS is essential for rBCV biogenesis, as VirB-deficient mutants are stalled in eBCVs and cannot mediate rBCV biogenesis. This has precluded analysis of whether the VirB apparatus also drives subsequent stages of theBrucellaintracellular cycle. To address this issue, we have generated aB. abortusstrain in which VirB T4SS function is conditionally controlled via anhydrotetracycline (ATc)-dependent complementation of a deletion of thevirB11gene encoding the VirB11 ATPase. We show in murine bone marrow-derived macrophages (BMMs) that early VirB production is essential for optimal rBCV biogenesis and bacterial replication. Transient expression ofvirB11prior to infection was sufficient to mediate normal rBCV biogenesis and bacterial replication but led to T4SS inactivation and decreased aBCV formation and bacterial release, indicating that these postreplication stages are also T4SS dependent. Hence, our findings support the hypothesis of additional, postreplication roles of type IV secretion in theBrucellaintracellular cycle.IMPORTANCEMany intracellular bacterial pathogens encode specialized secretion systems that deliver effector proteins into host cells to mediate the multiple stages of their intracellular cycles. Because these intracellular events occur sequentially, classical genetic approaches cannot address the late roles that these apparatuses play, as secretion-deficient mutants cannot proceed past their initial defect. Here we have designed a functionally controllable VirB type IV secretion system (T4SS) in the bacterial pathogenBrucella abortusto decipher its temporal requirements during the bacterium’s intracellular cycle in macrophages. By controlling production of the VirB11 ATPase, which energizes the T4SS, we show not only that this apparatus is required early to generate theBrucellareplicative organelle but also that it contributes to completion of the bacterium’s cycle and bacterial egress. Our findings expand upon the pathogenic functions of theBrucellaVirB T4SS and illustrate targeting of secretion ATPases as a useful strategy to manipulate the activity of bacterial secretion systems.

scholarly journals Brucella abortus VirB12 Is Expressed during Infection but Is Not an Essential Component of the Type IV Secretion System

2005 ◽  
Vol 73 (9) ◽  
pp. 6048-6054 ◽  
Author(s):  
Yao-Hui Sun ◽  
Hortensia G. Rolán ◽  
Andreas B. den Hartigh ◽  
David Sondervan ◽  
Renée M. Tsolis
Keyword(s):  
Brucella Abortus ◽  
Secretion System ◽  
Splenic Tissue ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Deletion Mutants ◽  
Wild Type ◽  
Intracellular Replication ◽  
Type Iv

ABSTRACT The Brucella abortus virB operon, consisting of 11 genes, virB1 to virB11, and two putative genes, orf12 (virB12) and orf13, encodes a type IV secretion system (T4SS) that is required for intracellular replication and persistent infection in the mouse model. This study was undertaken to determine whether orf12 (virB12) encodes an essential part of the T4SS apparatus. The virB12 gene was found to encode a 17-kDa protein, which was detected in vitro in B. abortus grown to stationary phase. Mice infected with B. abortus 2308 produced an antibody response to the protein encoded by virB12, showing that this gene is expressed during infection. Expression of virB12 was not required for survival in J774 macrophages. VirB12 was also dispensable for the persistence of B. abortus, B. melitensis, and B. suis in mice up to 4 weeks after infection, since deletion mutants lacking virB12 were recovered from splenic tissue at wild-type levels. These results show that VirB12 is not essential for the persistence of the human-pathogenic Brucella spp. in the mouse and macrophage models of infection.

scholarly journals VirB3 to VirB6 and VirB8 to VirB11, but Not VirB7, Are Essential for Mediating Persistence of Brucella in the Reticuloendothelial System

2008 ◽  
Vol 190 (13) ◽  
pp. 4427-4436 ◽  
Author(s):  
Andreas B. den Hartigh ◽  
Hortensia G. Rolán ◽  
Maarten F. de Jong ◽  
Renée M. Tsolis
Keyword(s):  
Brucella Abortus ◽  
Reticuloendothelial System ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Open Reading Frames ◽  
Type Iv Secretion System ◽  
Type Iv ◽  
Virulence Trait ◽  
Reading Frames

ABSTRACT The Brucella abortus virB locus contains 12 open reading frames, termed virB1 through virB12, which encode a type IV secretion system. Polar mutations in the virB locus markedly reduce the ability of B. abortus to survive in cultured macrophages or to persist in organs of mice. While a nonpolar deletion of the virB2 gene reduces survival in cultured macrophages and in organs of mice, a nonpolar deletion of virB1 only reduces survival in macrophages, whereas virB12 is dispensable for either virulence trait. Here we investigated the role of the remaining genes in the virB locus during survival in macrophages and virulence in mice. Mutants carrying nonpolar deletions of the virB3, virB4, virB5, virB6, virB7, virB8, virB9, virB10, or virB11 gene were constructed and characterized. All mutations reduced the ability of B. abortus to survive in J774A.1 mouse macrophage-like cells to a degree similar to that caused by a deletion of the entire virB locus. Deletion of virB3, virB4, virB5, virB6, virB8, virB9, virB10, or virB11 markedly reduced the ability of B. abortus to persist in the spleens of mice at 8 weeks after infection. Interestingly, deletion of virB7 did not reduce the ability of B. abortus to persist in spleens of mice. We conclude that virB2, virB3, virB4, virB5, virB6, virB8, virB9, virB10, and virB11 are essential for virulence of B. abortus in mice, while functions encoded by the virB1, virB7, and virB12 genes are not required for persistence in organs with this animal model.

scholarly journals Deletion of the type IV secretion system promoter VirB in Brucella abortus A19 strain attenuated the virulence of the bacteria and promotes autophagy

2021 ◽  
Author(s):  
XiaoYu Deng ◽  
Jinke He ◽  
Yueli Wang ◽  
Qin Yang ◽  
Ji Hai Yi ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Mutant Strain ◽  
Brucella Abortus ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Promoter Deletion ◽  
Type Iv ◽  
Related Proteins ◽  
The Impact

Brucella abortus is a Gram-negative intracellular parasite bacteria causing serious health hazards in humans and animals. The type IV secretion system (T4SS), encoded by the virB promoter, has been identified as an important virulence factor for Brucella abortus, but the impact on Brucella abortus A19 remains unclear. In this study, the T4SS of Brucella abortus A19 was inactivated by deleting the virB promoter, resulting in a mutant strain A19ΔvirB. Real-time PCR and Western-blotting analysis demonstrated that T4SS-related proteins were not expressed after virB promoter deletion. Moreover, the survival rate of A19 in high salt and strong acidic environments was decreased after virB promoter deletion. Compared to the parental strain A19, the A19ΔvirB mutant strain showed reduced growth rate in TSB, decreased invasion ability to macrophages and dendritic cells, and reduced virulence of the mutant strain in macrophages, dendritic cells and mice. In addition, the A19ΔvirB mutant strain showed enhanced autophagy on macrophages and dendritic cells compared with A19, and the A19ΔvirB mutant strain was able to upregulate IL-6 and downregulate IL-10 in macrophages. These data help us to better understand the T4SS of the A19 vaccine strain and contribute to our efforts to improve Brucella vaccines.

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