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Jane E Koehler - One of the best experts on this subject based on the ideXlab platform.
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the bartonella quintana extracytoplasmic function Sigma Factor rpoe has a role in bacterial adaptation to the arthropod vector environment
Journal of Bacteriology, 2013Co-Authors: Stephanie Abromaitis, Jane E KoehlerAbstract:Bartonella quintana is a vector-borne bacterial pathogen that causes fatal disease in humans. During the infectious cycle, B. quintana transitions from the hemin-restricted human bloodstream to the hemin-rich body louse vector. Because extracytoplasmic function (ECF) Sigma Factors often regulate adaptation to environmental changes, we hypothesized that a previously unstudied B. quintana ECF Sigma Factor, RpoE, is involved in the transition from the human host to the body louse vector. The genomic context of B. quintana rpoE identified it as a member of the ECF15 family of Sigma Factors found only in alphaproteobacteria. ECF15 Sigma Factors are believed to be the master regulators of the general stress response in alphaproteobacteria. In this study, we examined the B. quintana RpoE response to two stressors that are encountered in the body louse vector environment, a decreased temperature and an increased hemin concentration. We determined that the expression of rpoE is significantly upregulated at the body louse (28°C) versus the human host (37°C) temperature. rpoE expression also was upregulated when B. quintana was exposed to high hemin concentrations. In vitro and in vivo analyses demonstrated that RpoE function is regulated by a mechanism involving the anti-Sigma Factor NepR and the response regulator PhyR. The ΔrpoE ΔnepR mutant strain of B. quintana established that RpoE-mediated transcription is important in mediating the tolerance of B. quintana to high hemin concentrations. We present the first analysis of an ECF15 Sigma Factor in a vector-borne human pathogen and conclude that RpoE has a role in the adaptation of B. quintana to the hemin-rich arthropod vector environment.
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the bartonella quintana extracytoplasmic function Sigma Factor rpoe has a role in bacterial adaptation to the arthropod vector environment
Journal of Bacteriology, 2013Co-Authors: Stephanie Abromaitis, Jane E KoehlerAbstract:Bartonella quintana is a vector-borne bacterial pathogen that causes fatal disease in humans. During the infectious cycle, B. quintana transitions from the hemin-restricted human bloodstream to the hemin-rich body louse vector. Because extracytoplasmic function (ECF) Sigma Factors often regulate adaptation to environmental changes, we hypothesized that a previously unstudied B. quintana ECF Sigma Factor, RpoE, is involved in the transition from the human host to the body louse vector. The genomic context of B. quintana rpoE identified it as a member of the ECF15 family of Sigma Factors found only in alphaproteobacteria. ECF15 Sigma Factors are believed to be the master regulators of the general stress response in alphaproteobacteria. In this study, we examined the B. quintana RpoE response to two stressors that are encountered in the body louse vector environment, a decreased temperature and an increased hemin concentration. We determined that the expression of rpoE is significantly upregulated at the body louse (28°C) versus the human host (37°C) temperature. rpoE expression also was upregulated when B. quintana was exposed to high hemin concentrations. In vitro and in vivo analyses demonstrated that RpoE function is regulated by a mechanism involving the anti-Sigma Factor NepR and the response regulator PhyR. The ΔrpoE ΔnepR mutant strain of B. quintana established that RpoE-mediated transcription is important in mediating the tolerance of B. quintana to high hemin concentrations. We present the first analysis of an ECF15 Sigma Factor in a vector-borne human pathogen and conclude that RpoE has a role in the adaptation of B. quintana to the hemin-rich arthropod vector environment.
Stephanie Abromaitis - One of the best experts on this subject based on the ideXlab platform.
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the bartonella quintana extracytoplasmic function Sigma Factor rpoe has a role in bacterial adaptation to the arthropod vector environment
Journal of Bacteriology, 2013Co-Authors: Stephanie Abromaitis, Jane E KoehlerAbstract:Bartonella quintana is a vector-borne bacterial pathogen that causes fatal disease in humans. During the infectious cycle, B. quintana transitions from the hemin-restricted human bloodstream to the hemin-rich body louse vector. Because extracytoplasmic function (ECF) Sigma Factors often regulate adaptation to environmental changes, we hypothesized that a previously unstudied B. quintana ECF Sigma Factor, RpoE, is involved in the transition from the human host to the body louse vector. The genomic context of B. quintana rpoE identified it as a member of the ECF15 family of Sigma Factors found only in alphaproteobacteria. ECF15 Sigma Factors are believed to be the master regulators of the general stress response in alphaproteobacteria. In this study, we examined the B. quintana RpoE response to two stressors that are encountered in the body louse vector environment, a decreased temperature and an increased hemin concentration. We determined that the expression of rpoE is significantly upregulated at the body louse (28°C) versus the human host (37°C) temperature. rpoE expression also was upregulated when B. quintana was exposed to high hemin concentrations. In vitro and in vivo analyses demonstrated that RpoE function is regulated by a mechanism involving the anti-Sigma Factor NepR and the response regulator PhyR. The ΔrpoE ΔnepR mutant strain of B. quintana established that RpoE-mediated transcription is important in mediating the tolerance of B. quintana to high hemin concentrations. We present the first analysis of an ECF15 Sigma Factor in a vector-borne human pathogen and conclude that RpoE has a role in the adaptation of B. quintana to the hemin-rich arthropod vector environment.
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the bartonella quintana extracytoplasmic function Sigma Factor rpoe has a role in bacterial adaptation to the arthropod vector environment
Journal of Bacteriology, 2013Co-Authors: Stephanie Abromaitis, Jane E KoehlerAbstract:Bartonella quintana is a vector-borne bacterial pathogen that causes fatal disease in humans. During the infectious cycle, B. quintana transitions from the hemin-restricted human bloodstream to the hemin-rich body louse vector. Because extracytoplasmic function (ECF) Sigma Factors often regulate adaptation to environmental changes, we hypothesized that a previously unstudied B. quintana ECF Sigma Factor, RpoE, is involved in the transition from the human host to the body louse vector. The genomic context of B. quintana rpoE identified it as a member of the ECF15 family of Sigma Factors found only in alphaproteobacteria. ECF15 Sigma Factors are believed to be the master regulators of the general stress response in alphaproteobacteria. In this study, we examined the B. quintana RpoE response to two stressors that are encountered in the body louse vector environment, a decreased temperature and an increased hemin concentration. We determined that the expression of rpoE is significantly upregulated at the body louse (28°C) versus the human host (37°C) temperature. rpoE expression also was upregulated when B. quintana was exposed to high hemin concentrations. In vitro and in vivo analyses demonstrated that RpoE function is regulated by a mechanism involving the anti-Sigma Factor NepR and the response regulator PhyR. The ΔrpoE ΔnepR mutant strain of B. quintana established that RpoE-mediated transcription is important in mediating the tolerance of B. quintana to high hemin concentrations. We present the first analysis of an ECF15 Sigma Factor in a vector-borne human pathogen and conclude that RpoE has a role in the adaptation of B. quintana to the hemin-rich arthropod vector environment.
Hongwei D Yu - One of the best experts on this subject based on the ideXlab platform.
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pyrimidine biosynthesis regulates the small colony variant and mucoidy in pseudomonas aeruginosa through Sigma Factor competition
Journal of Bacteriology, 2018Co-Authors: Roy Al Ahmar, Hongwei D Yu, Brandon D KirbyAbstract:ABSTRACT Mucoidy due to alginate overproduction by the Gram-negative bacterium Pseudomonas aeruginosa facilitates chronic lung infections in patients with cystic fibrosis (CF). We previously reported that disruption in de novo synthesis of pyrimidines resulted in conversion to a nonmucoid small-colony variant (SCV) in the mucoid P. aeruginosa strain (PAO581), which has a truncated anti-Sigma Factor, MucA25, that cannot sequester Sigma Factor AlgU (AlgT). Here, we showed that supplementation with the nitrogenous bases uracil or cytosine in growth medium complemented the SCV to normal growth, and nonmucoidy to mucoidy, in these mucA25 mutants. This conversion was associated with an increase in intracellular levels of UMP and UTP suggesting that nucleotide restoration occurred via a salvage pathway. In addition, supplemented pyrimidines caused an increase in activity of the alginate biosynthesis promoter (PalgD), but had no effect on PalgU, which controls transcription of algU. Cytosolic levels of AlgU were not influenced by uracil supplementation, yet levels of RpoN, a Sigma Factor that regulates nitrogen metabolism, increased with disruption of pyrimidine synthesis and decreased after supplementation of uracil. This suggested that an elevated level of RpoN in SCV may block alginate biosynthesis. To support this, we observed that overexpressing rpoN resulted in a phenotypic switch to nonmucoidy in PAO581 and in mucoid clinical isolates. Furthermore, transcription of an RpoN-regulated promoter increased in the mutants and decreased after uracil supplementation. These results suggest that the balance of RpoN and AlgU levels may regulate growth from SCV to mucoidy through Sigma Factor competition for PalgD. IMPORTANCE Chronic lung infections with P. aeruginosa are the main cause of morbidity and mortality in patients with cystic fibrosis. This bacterium overproduces a capsular polysaccharide called alginate (also known as mucoidy), which aids in bacterial persistence in the lungs and in resistance to therapeutic regimens and host immune responses. The current study explores a previously unknown link between pyrimidine biosynthesis and mucoidy at the level of transcriptional regulation. Identifying/characterizing this link could provide novel targets for the control of bacterial growth and mucoidy. Inhibiting mucoidy may improve antimicrobial efficacy and facilitate host defenses to clear the noncapsulated P. aeruginosa bacteria, leading to improved prognosis for patients with cystic fibrosis.
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analysis of the pseudomonas aeruginosa regulon controlled by the sensor kinase kinb and Sigma Factor rpon
Journal of Bacteriology, 2012Co-Authors: Heath F Damron, Joshua P Owings, Yuta Okkotsu, Jill R Schurr, John J Varga, Michael J Schurr, Joanna B. Goldberg, Hongwei D YuAbstract:Alginate overproduction by Pseudomonas aeruginosa, also known as mucoidy, is associated with chronic endobronchial infections in cystic fibrosis. Alginate biosynthesis is initiated by the extracytoplasmic function Sigma Factor (σ22; AlgU/AlgT). In the wild-type (wt) nonmucoid strains, such as PAO1, AlgU is sequestered to the cytoplasmic membrane by the anti-Sigma Factor MucA that inhibits alginate production. One mechanism underlying the conversion to mucoidy is mutation of mucA. However, the mucoid conversion can occur in wt mucA strains via the degradation of MucA by activated intramembrane proteases AlgW and/or MucP. Previously, we reported that the deletion of the sensor kinase KinB in PAO1 induces an AlgW-dependent proteolysis of MucA, resulting in alginate overproduction. This type of mucoid induction requires the alternate Sigma Factor RpoN (σ54). To determine the RpoN-dependent KinB regulon, microarray and proteomic analyses were performed on a mucoid kinB mutant and an isogenic nonmucoid kinB rpoN double mutant. In the kinB mutant of PAO1, RpoN controlled the expression of approximately 20% of the genome. In addition to alginate biosynthetic and regulatory genes, KinB and RpoN also control a large number of genes including those involved in carbohydrate metabolism, quorum sensing, iron regulation, rhamnolipid production, and motility. In an acute pneumonia murine infection model, BALB/c mice exhibited increased survival when challenged with the kinB mutant relative to survival with PAO1 challenge. Together, these data strongly suggest that KinB regulates virulence Factors important for the development of acute pneumonia and conversion to mucoidy.
Jorn Kalinowski - One of the best experts on this subject based on the ideXlab platform.
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transcriptional regulation of the operon encoding stress responsive ecf Sigma Factor sigh and its anti Sigma Factor rsha and control of its regulatory network in corynebacterium glutamicum
BMC Genomics, 2012Co-Authors: Tobias Busche, Radoslav Silar, Martina Picmanova, Miroslav Patek, Jorn KalinowskiAbstract:The expression of genes in Corynebacterium glutamicum, a Gram-positive non-pathogenic bacterium used mainly for the industrial production of amino acids, is regulated by seven different Sigma Factors of RNA polymerase, including the stress-responsive ECF-Sigma Factor SigH. The sigH gene is located in a gene cluster together with the rshA gene, putatively encoding an anti-Sigma Factor. The aim of this study was to analyze the transcriptional regulation of the sigH and rshA gene cluster and the effects of RshA on the SigH regulon, in order to refine the model describing the role of SigH and RshA during stress response. Transcription analyses revealed that the sigH gene and rshA gene are cotranscribed from four sigH housekeeping promoters in C. glutamicum. In addition, a SigH-controlled rshA promoter was found to only drive the transcription of the rshA gene. To test the role of the putative anti-Sigma Factor gene rshA under normal growth conditions, a C. glutamicum rshA deletion strain was constructed and used for genome-wide transcription profiling with DNA microarrays. In total, 83 genes organized in 61 putative transcriptional units, including those previously detected using sigH mutant strains, exhibited increased transcript levels in the rshA deletion mutant compared to its parental strain. The genes encoding proteins related to disulphide stress response, heat stress proteins, components of the SOS-response to DNA damage and proteasome components were the most markedly upregulated gene groups. Altogether six SigH-dependent promoters upstream of the identified genes were determined by primer extension and a refined consensus promoter consisting of 45 original promoter sequences was constructed. The rshA gene codes for an anti-Sigma Factor controlling the function of the stress-responsive Sigma Factor SigH in C. glutamicum. Transcription of rshA from a SigH-dependent promoter may serve to quickly shutdown the SigH-dependent stress response after the cells have overcome the stress condition. Here we propose a model of the regulation of oxidative and heat stress response including redox homeostasis by SigH, RshA and the thioredoxin system.
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the alternative Sigma Factor sigb of corynebacterium glutamicum modulates global gene expression during transition from exponential growth to stationary phase
BMC Genomics, 2007Co-Authors: Christof Larisch, Diana Nakunst, Andrea T Huser, Andreas Tauch, Jorn KalinowskiAbstract:Corynebacterium glutamicum is a gram-positive soil bacterium widely used for the industrial production of amino acids. There is great interest in the examination of the molecular mechanism of transcription control. One of these control mechanisms are Sigma Factors. C. glutamicum ATCC 13032 has seven putative Sigma Factor-encoding genes, including sigA and sigB. The sigA gene encodes the essential primary Sigma Factor of C. glutamicum and is responsible for promoter recognition of house-keeping genes. The sigB gene codes for the non-essential Sigma Factor SigB that has a proposed role in stress reponse. The sigB gene expression was highest at transition between exponential growth and stationary phase, when the amount of sigA mRNA was already decreasing. Genome-wide transcription profiles of the wild-type and the sigB mutant were recorded by comparative DNA microarray hybridizations. The data indicated that the mRNA levels of 111 genes are significantly changed in the sigB-proficient strain during the transition phase, whereas the expression profile of the sigB-deficient strain showed only minor changes (26 genes). The genes that are higher expressed during transition phase only in the sigB-proficient strain mainly belong to the functional categories amino acid metabolism, carbon metabolism, stress defense, membrane processes, and phosphorus metabolism. The transcription start points of six of these genes were determined and the deduced promoter sequences turned out to be indistinguishable from that of the consensus promoter recognized by SigA. Real-time reverse transcription PCR assays revealed that the expression profiles of these genes during growth were similar to that of the sigB gene itself. In the sigB mutant, however, the transcription profiles resembled that of the sigA gene encoding the house-keeping Sigma Factor. During transition phase, the sigB gene showed an enhanced expression, while simultaneously the sigA mRNA decreased in abundance. This might cause a replacement of SigA by SigB at the RNA polymerase core enzyme and in turn results in increased expression of genes relevant for the transition and the stationary phase, either to cope with nutrient limitation or with the accompanying oxidative stress. The increased expression of genes encoding anti-oxidative or protection functions also prepares the cell for upcoming limitations and environmental stresses.
Joanna B. Goldberg - One of the best experts on this subject based on the ideXlab platform.
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overproduction of the algt Sigma Factor is lethal to mucoid pseudomonas aeruginosa
Journal of Bacteriology, 2020Co-Authors: Ashley R Cross, Vishnu Raghuram, Zihuan Wang, Debayan Dey, Joanna B. GoldbergAbstract:ABSTRACT Pseudomonas aeruginosa isolates from chronic lung infections often overproduce alginate, giving rise to the mucoid phenotype. Isolation of mucoid strains from chronic lung infections correlates with a poor patient outcome. The most common mutation that causes the mucoid phenotype is called mucA22 and results in a truncated form of the anti-Sigma Factor MucA that is continuously subjected to proteolysis. When a functional MucA is absent, the cognate Sigma Factor, AlgT, is no longer sequestered and continuously transcribes the alginate biosynthesis operon, leading to alginate overproduction. In this work, we report that in the absence of wild-type MucA, providing exogenous AlgT is toxic. This is intriguing, since mucoid strains endogenously possess high levels of AlgT. Furthermore, we show that suppressors of toxic AlgT production have mutations in mucP, a protease involved in MucA degradation, and provide the first atomistic model of MucP. Based on our findings, we speculate that mutations in mucP stabilize the truncated form of MucA22, rendering it functional and therefore able to reduce toxicity by properly sequestering AlgT. IMPORTANCEPseudomonas aeruginosa is an opportunistic bacterial pathogen capable of causing chronic lung infections. Phenotypes important for the long-term persistence and adaption to this unique lung ecosystem are largely regulated by the AlgT Sigma Factor. Chronic infection isolates often contain mutations in the anti-Sigma Factor mucA, resulting in uncontrolled AlgT and continuous production of alginate in addition to the expression of ∼300 additional genes. Here, we report that in the absence of wild-type MucA, AlgT overproduction is lethal and that suppressors of toxic AlgT production have mutations in the MucA protease, MucP. Since AlgT contributes to the establishment of chronic infections, understanding how AlgT is regulated will provide vital information on how P. aeruginosa is capable of causing long-term infections.
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overproduction of the algt Sigma Factor is lethal to mucoid pseudomonas aeruginosa
bioRxiv, 2020Co-Authors: Ashley R Cross, Vishnu Raghuram, Zihuan Wang, Debayan Dey, Joanna B. GoldbergAbstract:Pseudomonas aeruginosa isolates from chronic lung infections often overproduce alginate, giving rise to the mucoid phenotype. Isolation of mucoid strains from chronic lung infections correlates with a poor patient outcome. The most common mutation that causes the mucoid phenotype is called mucA22 and results in a truncated form of the anti-Sigma Factor MucA that is continuously subjected to proteolysis. When a functional MucA is absent, the cognate Sigma Factor, AlgT, is no longer sequestered and continuously transcribes the alginate biosynthesis operon leading to alginate overproduction. In this work, we report that in the absence of wild-type MucA, providing exogenous AlgT is toxic. This is intriguing since mucoid strains endogenously possess high levels of AlgT. Furthermore, we show that suppressors of toxic AlgT production have mutations in mucP, a protease involved in MucA degradation, and provide the first atomistic model of MucP. Our findings support a model where mutations in mucP stabilize the truncated form of MucA22 rendering it functional and therefore able to reduce toxicity by properly sequestering AlgT.
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analysis of the pseudomonas aeruginosa regulon controlled by the sensor kinase kinb and Sigma Factor rpon
Journal of Bacteriology, 2012Co-Authors: Heath F Damron, Joshua P Owings, Yuta Okkotsu, Jill R Schurr, John J Varga, Michael J Schurr, Joanna B. Goldberg, Hongwei D YuAbstract:Alginate overproduction by Pseudomonas aeruginosa, also known as mucoidy, is associated with chronic endobronchial infections in cystic fibrosis. Alginate biosynthesis is initiated by the extracytoplasmic function Sigma Factor (σ22; AlgU/AlgT). In the wild-type (wt) nonmucoid strains, such as PAO1, AlgU is sequestered to the cytoplasmic membrane by the anti-Sigma Factor MucA that inhibits alginate production. One mechanism underlying the conversion to mucoidy is mutation of mucA. However, the mucoid conversion can occur in wt mucA strains via the degradation of MucA by activated intramembrane proteases AlgW and/or MucP. Previously, we reported that the deletion of the sensor kinase KinB in PAO1 induces an AlgW-dependent proteolysis of MucA, resulting in alginate overproduction. This type of mucoid induction requires the alternate Sigma Factor RpoN (σ54). To determine the RpoN-dependent KinB regulon, microarray and proteomic analyses were performed on a mucoid kinB mutant and an isogenic nonmucoid kinB rpoN double mutant. In the kinB mutant of PAO1, RpoN controlled the expression of approximately 20% of the genome. In addition to alginate biosynthetic and regulatory genes, KinB and RpoN also control a large number of genes including those involved in carbohydrate metabolism, quorum sensing, iron regulation, rhamnolipid production, and motility. In an acute pneumonia murine infection model, BALB/c mice exhibited increased survival when challenged with the kinB mutant relative to survival with PAO1 challenge. Together, these data strongly suggest that KinB regulates virulence Factors important for the development of acute pneumonia and conversion to mucoidy.
