scholarly journals Identification of an Orphan Response Regulator Required for the Virulence of Francisella spp. and Transcription of Pathogenicity Island Genes

2007 ◽  
Vol 75 (7) ◽  
pp. 3305-3314 ◽  
Author(s):  
Nrusingh P. Mohapatra ◽  
Shilpa Soni ◽  
Brian L. Bell ◽  
Richard Warren ◽  
Robert K. Ernst ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mutant Strain ◽  
Lipid A ◽  
Response Regulator ◽  
Model Organism ◽  
Virulence Gene ◽  
Pathogenicity Island ◽  
Effective Vaccine ◽  
Gene Encoding ◽  
Virulence Gene Expression

ABSTRACT Francisella tularensis is a category A agent of biowarfare/biodefense. Little is known about the regulation of virulence gene expression in Francisella spp. Comparatively few regulatory factors exist in Francisella, including those belonging to two-component systems (TCS). However, orphan members of typical TCS can be identified. To determine if orphan TCS members affect Francisella gene expression, a gene encoding a product with high similarity to the Salmonella PmrA response regulator (FTT1557c/FNU0663.2) was deleted in Francisella novicida (a model organism for F. tularensis). The F. novicida pmrA mutant was defective in survival/growth within human and murine macrophage cell lines and was 100% defective in virulence in mice at a dose of up to 108 CFU. In addition, the mutant strain demonstrated increased susceptibility to antimicrobial peptide killing, but no differences were observed between the lipid A of the mutant and the parental strain, as has been observed with pmrA mutants of other microbes. The F. novicida pmrA mutant was 100% protective as a single-dose vaccine when challenge was with 106 CFU of F. novicida but did not protect against type A Schu S4 wild-type challenge. DNA microarray analysis identified 65 genes regulated by PmrA. The majority of these genes were located in the region surrounding pmrA or within the Francisella pathogenicity island (FPI). These FPI genes are also regulated by MglA, but MglA does not regulate pmrA, nor does PmrA regulate MglA. Thus, the orphan response regulator PmrA is an important factor in controlling virulence in F. novicida, and a pmrA mutant strain is an effective vaccine against homologous challenge.

scholarly journals Use of a Phosphorylation Site Mutant To Identify Distinct Modes of Gene Repression by the Control of Virulence Regulator (CovR) in Streptococcus pyogenes

2017 ◽  
Vol 199 (18) ◽  
Author(s):  
Nicola Horstmann ◽  
Pranoti Sahasrabhojane ◽  
Hui Yao ◽  
Xiaoping Su ◽  
Samuel A. Shelburne
Keyword(s):  
Gene Expression ◽  
Streptococcus Pyogenes ◽  
Response Regulator ◽  
Phosphorylation Site ◽  
Virulence Gene ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Superficial Skin ◽  
Virulence Regulator ◽  
The Impact

ABSTRACT Control of the virulence regulator/sensor kinase (CovRS) two-component system (TCS) serves as a model for investigating the impact of signaling pathways on the pathogenesis of Gram-positive bacteria. However, the molecular mechanisms by which CovR, an OmpR/PhoB family response regulator, controls virulence gene expression are poorly defined, partly due to the labile nature of its aspartate phosphorylation site. To better understand the regulatory effect of phosphorylated CovR, we generated the phosphorylation site mutant strain 10870-CovR-D53E, which we predicted to have a constitutive CovR phosphorylation phenotype. Interestingly, this strain showed CovR activity only for a subset of the CovR regulon, which allowed for classification of CovR-influenced genes into D53E-regulated and D53E-nonregulated groups. Inspection of the promoter sequences of genes belonging to each group revealed distinct promoter architectures with respect to the location and number of putative CovR-binding sites. Electrophoretic mobility shift analysis demonstrated that recombinant CovR-D53E protein retains its ability to bind promoter DNA from both CovR-D53E-regulated and -nonregulated groups, implying that factors other than mere DNA binding are crucial for gene regulation. In fact, we found that CovR-D53E is incapable of dimerization, a process thought to be critical to OmpR/PhoB family regulator function. Thus, our global analysis of CovR-D53E indicates dimerization-dependent and dimerization-independent modes of CovR-mediated repression, thereby establishing distinct mechanisms by which this critical regulator coordinates virulence gene expression. IMPORTANCE Streptococcus pyogenes causes a wide variety of diseases, ranging from superficial skin and throat infections to life-threatening invasive infections. To establish these various disease manifestations, Streptococcus pyogenes requires tightly coordinated production of its virulence factor repertoire. Here, the response regulator CovR plays a crucial role. As an OmpR/PhoB family member, CovR is activated by phosphorylation on a conserved aspartate residue, leading to protein dimerization and subsequent binding to operator sites. Our transcriptome analysis using the monomeric phosphorylation mimic mutant CovR-D53E broadens this general notion by revealing dimerization-independent repression of a subset of CovR-regulated genes. Combined with promoter analyses, these data suggest distinct mechanisms of CovR transcriptional control, which allow for differential expression of virulence genes in response to environmental cues.

scholarly journals Reconstitution of Acetosyringone-Mediated Agrobacterium tumefaciens Virulence Gene Expression in the Heterologous Host Escherichia coli

2001 ◽  
Vol 183 (12) ◽  
pp. 3704-3711 ◽  
Author(s):  
Scott M. Lohrke ◽  
Hongjiang Yang ◽  
Shouguang Jin
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Agrobacterium Tumefaciens ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Dependent Manner ◽  
Gene Encoding ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Glucose Binding

ABSTRACT The ability to utilize Escherichia coli as a heterologous system in which to study the regulation ofAgrobacterium tumefaciens virulence genes and the mechanism of transfer DNA (T-DNA) transfer would provide an important tool to our understanding and manipulation of these processes. We have previously reported that the rpoA gene encoding the alpha subunit of RNA polymerase is required for the expression of lacZ gene under the control of virB promoter (virBp::lacZ) in E. colicontaining a constitutively active virG gene [virG(Con)]. Here we show that an RpoA hybrid containing the N-terminal 247 residues from E. coli and the C-terminal 89 residues from A. tumefaciens was able to significantly express virBp::lacZ in E. coli in a VirG(Con)-dependent manner. Utilization oflac promoter-driven virA and virGin combination with the A. tumefaciens rpoA construct resulted in significant inducer-mediated expression of thevirBp::lacZ fusion, and the level ofvirBp::lacZ expression was positively correlated to the copy number of the rpoA construct. This expression was dependent on VirA, VirG, temperature, and, to a lesser extent, pH, which is similar to what is observed in A. tumefaciens. Furthermore, the effect of sugars on virgene expression was observed only in the presence of thechvE gene, suggesting that the glucose-binding protein ofE. coli, a homologue of ChvE, does not interact with the VirA molecule. We also evaluated other phenolic compounds in induction assays and observed significant expression with syringealdehyde, a low level of expression with acetovanillone, and no expression with hydroxyacetophenone, similar to what occurs in A. tumefaciens strain A348 from which the virA clone was derived. These data support the notion that VirA directly senses the phenolic inducer. However, the overall level of expression of thevir genes in E. coli is less than what is observed in A. tumefaciens, suggesting that additional gene(s) from A. tumefaciens may be required for the full expression of virulence genes in E. coli.

scholarly journals The response regulator ResD modulates virulence gene expression in response to carbohydrates in Listeria monocytogenes

2006 ◽  
Vol 61 (6) ◽  
pp. 1622-1635 ◽  
Author(s):  
Marianne H. Larsen ◽  
Birgitte H. Kallipolitis ◽  
Janne K. Christiansen ◽  
John E. Olsen ◽  
Hanne Ingmer
Keyword(s):  
Gene Expression ◽  
Listeria Monocytogenes ◽  
Response Regulator ◽  
Virulence Gene ◽  
Virulence Gene Expression

scholarly journals The Global Regulator CodY Regulates Toxin Gene Expression in Bacillus anthracis and Is Required for Full Virulence

2009 ◽  
Vol 77 (10) ◽  
pp. 4437-4445 ◽  
Author(s):  
Willem van Schaik ◽  
Alice Château ◽  
Marie-Agnès Dillies ◽  
Jean-Yves Coppée ◽  
Abraham L. Sonenshein ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bacillus Anthracis ◽  
Mutant Strain ◽  
Virulence Gene ◽  
Etiologic Agent ◽  
Toxin Gene ◽  
Promoter Regions ◽  
Virulence Gene Expression ◽  
Toxin Gene Expression ◽  
Virulence Regulator

ABSTRACT In gram-positive bacteria, CodY is an important regulator of genes whose expression changes upon nutrient limitation and acts as a repressor of virulence gene expression in some pathogenic species. Here, we report the role of CodY in Bacillus anthracis, the etiologic agent of anthrax. Disruption of codY completely abolished virulence in a toxinogenic, noncapsulated strain, indicating that the activity of CodY is required for full virulence of B. anthracis. Global transcriptome analysis of a codY mutant and the parental strain revealed extensive differences. These differences could reflect direct control for some genes, as suggested by the presence of CodY binding sequences in their promoter regions, or indirect effects via the CodY-dependent control of other regulatory proteins or metabolic rearrangements in the codY mutant strain. The differences included reduced expression of the anthrax toxin genes in the mutant strain, which was confirmed by lacZ reporter fusions and immunoblotting. The accumulation of the global virulence regulator AtxA protein was strongly reduced in the mutant strain. However, in agreement with the microarray data, expression of atxA, as measured using an atxA-lacZ transcriptional fusion and by assaying atxA mRNA, was not significantly affected in the codY mutant. An atxA-lacZ translational fusion was also unaffected. Overexpression of atxA restored toxin component synthesis in the codY mutant strain. These results suggest that CodY controls toxin gene expression by regulating AtxA accumulation posttranslationally.

scholarly journals ChvD, a Chromosomally Encoded ATP-Binding Cassette Transporter-Homologous Protein Involved in Regulation of Virulence Gene Expression in Agrobacterium tumefaciens

2001 ◽  
Vol 183 (11) ◽  
pp. 3310-3317 ◽  
Author(s):  
Zhenying Liu ◽  
Mark Jacobs ◽  
Dennis A. Schaff ◽  
Colleen A. McCullen ◽  
Andrew N. Binns
Keyword(s):  
Gene Expression ◽  
Agrobacterium Tumefaciens ◽  
Mutant Strain ◽  
Molecular Genetic ◽  
Constitutive Expression ◽  
Virulence Gene ◽  
Molecular Genetic Analysis ◽  
Atp Binding ◽  
Virulence Gene Expression ◽  
Atp Binding Cassette

ABSTRACT A yeast two-hybrid screen searching for chromosomally encoded proteins that interact with the Agrobacterium tumefaciensVirB8 protein was carried out. This screen identified an interaction candidate homologous to the partial sequence of a gene that had previously been identified in a transposon screen as a potential regulator of virG expression, chvD. In this report, the cloning of the entire chvD gene is described and the gene is sequenced and characterized. Insertion of a promoterless lacZ gene into the chvD locus greatly attenuated virulence and vir gene expression. Compared to that of the wild-type strain, growth of thechvD mutant was reduced in rich, but not minimal, medium. Expression of chvD, as monitored by expression of β-galactosidase activity from the chvD-lacZ fusion, occurred in both rich and minimal media as well as under conditions that induce virulence gene expression. The ChvD protein is highly homologous to a family of ATP-binding cassette transporters involved in antibiotic export from bacteria and has two complete Walker box motifs. Molecular genetic analysis demonstrated that disruption of either Walker A box, singly, does not inactivate this protein's effect on virulence but that mutations in both Walker A boxes renders it incapable of complementing a chvD mutant strain. Constitutive expression of virG in the chvDmutant strain restored virulence, supporting the hypothesis that ChvD controls virulence through effects on virG expression.

scholarly journals Depletion of Glucose Activates Catabolite Repression during Pneumonic Plague

2018 ◽  
Vol 200 (11) ◽  
Author(s):  
Jeremy T. Ritzert ◽  
Wyndham W. Lathem
Keyword(s):  
Gene Expression ◽  
Yersinia Pestis ◽  
Virulence Gene ◽  
Gene Encoding ◽  
Repressor Protein ◽  
Pneumonic Plague ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Glucose Levels ◽  
Catabolite Repressor

ABSTRACTBacterial pathogenesis depends on changes in metabolic and virulence gene expression in response to changes within a pathogen's environment. The plague-causing pathogen,Yersinia pestis, requires expression of the gene encoding the Pla protease for progression of pneumonic plague. The catabolite repressor protein Crp, a global transcriptional regulator, may serve as the activator ofplain response to changes within the lungs as disease progresses. By using gene reporter fusions, the spatial and temporal activation of thecrpandplapromoters was measured in a mouse model of pneumonic plague. In the lungs,crpwas highly expressed in bacteria found within large aggregates resembling biofilms, whileplaexpression increased over time independent of the aggregated state. Increased expression ofcrpandplacorrelated with a reduction in lung glucose levels. Deletion of the glucose-specific phosphotransferase system EIIBC (PtsG) ofY. pestisrescued glucose levels in the lungs, resulting in reduced expression of bothcrpandpla. We propose that activation ofplaexpression during pneumonic plague is driven by an increase of both Crp and cAMP levels following consumption of available glucose in the lungs byY. pestis. Thus, Crp operates as a sensor linking the nutritional environment of the host to regulation of virulence gene expression.IMPORTANCEUsingYersinia pestisas a model for pneumonia, we discovered that glucose is rapidly consumed, leading to a catabolite-repressive environment in the lungs. As a result, expression of the gene encoding the plasminogen activator protease, a target of the catabolite repressor protein required forY. pestispathogenesis, is activated. Interestingly, expression of the catabolite repressor protein itself was also increased in the absence of glucose but only in biofilms. The data presented here demonstrate how a bacterial pathogen senses changes within its environment to coordinate metabolism and virulence gene expression.

Vibrio harveyi virulence gene expression in vitro and in vivo during infection in black tiger shrimp Penaeus monodon

2020 ◽  
Vol 139 ◽  
pp. 153-160
Author(s):  
S Peeralil ◽  
TC Joseph ◽  
V Murugadas ◽  
PG Akhilnath ◽  
VN Sreejith ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Genes ◽  
Vibrio Harveyi ◽  
Penaeus Monodon ◽  
Challenge Test ◽  
Virulence Gene ◽  
Economic Losses ◽  
Virulence Gene Expression

Luminescent Vibrio harveyi is common in sea and estuarine waters. It produces several virulence factors and negatively affects larval penaeid shrimp in hatcheries, resulting in severe economic losses to shrimp aquaculture. Although V. harveyi is an important pathogen of shrimp, its pathogenicity mechanisms have yet to be completely elucidated. In the present study, isolates of V. harveyi were isolated and characterized from diseased Penaeus monodon postlarvae from hatcheries in Kerala, India, from September to December 2016. All 23 tested isolates were positive for lipase, phospholipase, caseinase, gelatinase and chitinase activity, and 3 of the isolates (MFB32, MFB71 and MFB68) showed potential for significant biofilm formation. Based on the presence of virulence genes, the isolates of V. harveyi were grouped into 6 genotypes, predominated by vhpA+ flaB+ ser+ vhh1- luxR+ vopD- vcrD+ vscN-. One isolate from each genotype was randomly selected for in vivo virulence experiments, and the LD50 ranged from 1.7 ± 0.5 × 103 to 4.1 ± 0.1 × 105 CFU ml-1. The expression of genes during the infection in postlarvae was high in 2 of the isolates (MFB12 and MFB32), consistent with the result of the challenge test. However, in MFB19, even though all genes tested were present, their expression level was very low and likely contributed to its lack of virulence. Because of the significant variation in gene expression, the presence of virulence genes alone cannot be used as a marker for pathogenicity of V. harveyi.

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