Redox sensing modulates the activity of ComE response regulator of Streptococcus mutans

2021 ◽  
Author(s):  
Hemendra Pal Singh Dhaked ◽  
Luyang Cao ◽  
Indranil Biswas
Keyword(s):  
Streptococcus Mutans ◽  
Stress Responses ◽  
Response Regulator ◽  
Aerobic Condition ◽  
Wild Type ◽  
Important Species ◽  
Fluorescence Studies ◽  
Two Component ◽  
Redox Sensing

Streptococcus mutans , a dental pathogen, encodes the ComDE two-component system comprised of a histidine kinase (ComD) and a response regulator (ComE). This system is necessary for production of bacteriocins and development of genetic competence. ComE interacts with its cognate promoters to activate the transcription of bacteriocin and competence related genes. Previous transcriptomic studies indicated that expressions of bacteriocin genes were upregulated in the presence of oxygen. To understand the relationship between the aerobic condition and bacteriocin expression, we analyzed the S. mutans ComE sequence and its close homologs. Surprisingly, we noticed the presence of cysteine (Cys) residues located at positions 200 and 229, which are highly conserved among the ComE homologs. Here we investigated the role of Cys residues of S. mutans ComE in the activation of bacteriocin transcription using the P nlmA promoter that expresses bacteriocin NlmA. We constructed both single mutants and double mutants by replacing the Cys residues with serine and performed complementation assays. We observed that the presence of Cys residues is essential for P nlmA activation. With purified ComE mutant proteins we found that ComE double mutants displayed a nearly two-fold lower association rate than wild-type ComE. Furthermore, ANS fluorescence studies indicated that the double mutants displayed wider conformation changes than wild-type ComE. Finally, we demonstrated that close streptococcal ComE homologs successfully activate the P nlmA expression in vivo . This is the first report suggesting that S. mutans ComE and its homologs can sense the oxidation status of the cell, a phenomenon similar to the AgrA system of Staphylococcus aureus but with different outcome. IMPORTANCE Streptococci are an important species that prefer to grow under anaerobic or microaerophilic environments. Studies have shown that streptococci growth in an aerobic environment generates oxidative stress responses by activating various defense systems including production of antimicrobial peptides called bacteriocins. This study highlights the importance of a two-component response regulator (ComE) that senses the aerobic environment and induces bacteriocin production in Streptococcus mutans , a dental pathogen. We believe increased bacteriocin secretion under aerobic conditions is necessary for survival and colonization of S. mutans in the oral cavity by inhibiting other competing organisms. Redox sensing by response regulator might be a wide-spread phenomenon, since two other ComE homologs from pathogenic streptococci that inhabit diverse environmental niches also perform a similar function.

scholarly journals Phosphorelay as the Sole Physiological Route of Signal Transmission by the Arc Two-Component System ofEscherichia coli

2000 ◽  
Vol 182 (13) ◽  
pp. 3858-3862 ◽  
Author(s):  
Ohsuk Kwon ◽  
Dimitris Georgellis ◽  
E. C. C. Lin
Keyword(s):  
Response Regulator ◽  
Signal Transmission ◽  
Phosphoryl Group ◽  
Sensor Kinase ◽  
Wild Type ◽  
Two Component System ◽  
Component System ◽  
Group Transfer ◽  
Two Component

ABSTRACT The Arc two-component system, comprising a tripartite sensor kinase (ArcB) and a response regulator (ArcA), modulates the expression of numerous genes involved in respiratory functions. In this study, the steps of phosphoryl group transfer from phosphorylated ArcB to ArcA were examined in vivo by using single copies of wild-type and mutantarcB alleles. The results indicate that the signal transmission occurs solely by His-Asp-His-Asp phosphorelay.

scholarly journals A VicRK Signal Transduction System in Streptococcus mutans Affects gtfBCD, gbpB, and ftf Expression, Biofilm Formation, and Genetic Competence Development

2005 ◽  
Vol 187 (12) ◽  
pp. 4064-4076 ◽  
Author(s):  
M. Dilani Senadheera ◽  
Bernard Guggenheim ◽  
Grace A. Spatafora ◽  
Yi-Chen Cathy Huang ◽  
Jison Choi ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Streptococcus Mutans ◽  
Response Regulator ◽  
In Vivo Studies ◽  
Adaptive Responses ◽  
Wild Type ◽  
Signal Transduction System ◽  
Promoter Regions ◽  
Expression Of Genes

ABSTRACT Bacteria exposed to transient host environments can elicit adaptive responses by triggering the differential expression of genes via two-component signal transduction systems. This study describes the vicRK signal transduction system in Streptococcus mutans. A vicK (putative histidine kinase) deletion mutant (SmuvicK) was isolated. However, a vicR (putative response regulator) null mutation was apparently lethal, since the only transformants isolated after attempted mutagenesis overexpressed all three genes in the vicRKX operon (Smuvic+). Compared with the wild-type UA159 strain, both mutants formed aberrant biofilms. Moreover, the vicK mutant biofilm formed in sucrose-supplemented medium was easily detachable relative to that of the parent. The rate of total dextran formation by this mutant was remarkably reduced compared to the wild type, whereas it was increased in Smuvic+. Based on real-time PCR, Smuvic+ showed increased gtfBCD, gbpB, and ftf expression, while a recombinant VicR fusion protein was shown to bind the promoter regions of the gtfB, gtfC, and ftf genes. Also, transformation efficiency in the presence or absence of the S. mutans competence-stimulating peptide was altered for the vic mutants. In vivo studies conducted using SmuvicK in a specific-pathogen-free rat model resulted in significantly increased smooth-surface dental plaque (Pearson-Filon statistic [PF], <0.001). While the absence of vicK did not alter the incidence of caries, a significant reduction in SmuvicK CFU counts was observed in plaque samples relative to that of the parent (PF, <0.001). Taken together, these findings support involvement of the vicRK signal transduction system in regulating several important physiological processes in S. mutans.

scholarly journals FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Wei Liu ◽  
Xue Bai ◽  
Yan Li ◽  
Haikun Zhang ◽  
Xiaoke Hu
Keyword(s):  
Signal Transduction ◽  
Host Plant ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Response Regulators ◽  
Free Living ◽  
Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

scholarly journals Functional reconstitution of the Salmonella typhimurium PhoQ histidine kinase sensor in proteoliposomes

2005 ◽  
Vol 390 (3) ◽  
pp. 769-776 ◽  
Author(s):  
Sarah Sanowar ◽  
Hervé Le Moual
Keyword(s):  
Salmonella Typhimurium ◽  
Histidine Kinase ◽  
Catalytic Domain ◽  
Response Regulator ◽  
Phosphoryl Group ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
High Concentrations

Two-component signal-transduction systems are widespread in bacteria. They are usually composed of a transmembrane histidine kinase sensor and a cytoplasmic response regulator. The PhoP/PhoQ two-component system of Salmonella typhimurium contributes to virulence by co-ordinating the adaptation to low concentrations of environmental Mg2+. Limiting concentrations of extracellular Mg2+ activate the PhoP/PhoQ phosphorylation cascade modulating the transcription of PhoP-regulated genes. In contrast, high concentrations of extracellular Mg2+ stimulate the dephosphorylation of the response regulator PhoP by the PhoQ kinase sensor. In the present study, we report the purification and functional reconstitution of PhoQHis, a PhoQ variant with a C-terminal His tag, into Escherichia coli liposomes. The functionality of PhoQHis was essentially similar to that of PhoQ as shown in vivo and in vitro. Purified PhoQHis was inserted into liposomes in a unidirectional orientation, with the sensory domain facing the lumen and the catalytic domain facing the extraluminal environment. Reconstituted PhoQHis exhibited all the catalytic activities that have been described for histidine kinase sensors. Reconstituted PhoQHis was capable of autokinase activity when incubated in the presence of Mg2+-ATP. The phosphoryl group could be transferred from reconstituted PhoQHis to PhoP. Reconstituted PhoQHis catalysed the dephosphorylation of phospho-PhoP and this activity was stimulated by the addition of extraluminal ADP.

scholarly journals A Novel Redox-Sensing Histidine Kinase That Controls Carbon Catabolite Repression inAzoarcussp. CIB

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
J. Andrés Valderrama ◽  
Helena Gómez-Álvarez ◽  
Zaira Martín-Moldes ◽  
M. Álvaro Berbís ◽  
F. Javier Cañada ◽  
...  
Keyword(s):  
Aromatic Compounds ◽  
Histidine Kinase ◽  
Catabolite Repression ◽  
Carbon Catabolite Repression ◽  
Response Regulator ◽  
Sensor Kinase ◽  
General Role ◽  
Two Component ◽  
Redox Switch ◽  
Redox Sensing

ABSTRACTWe have identified and characterized the AccS multidomain sensor kinase that mediates the activation of the AccR master regulator involved in carbon catabolite repression (CCR) of the anaerobic catabolism of aromatic compounds inAzoarcussp. CIB. A truncated AccS protein that contains only the soluble C-terminal autokinase module (AccS′) accounts for the succinate-dependent CCR control. In vitroassays with purified AccS′ revealed its autophosphorylation, phosphotransfer from AccS′∼P to the Asp60 residue of AccR, and the phosphatase activity toward its phosphorylated response regulator, indicating that the equilibrium between the kinase and phosphatase activities of AccS′ may control the phosphorylation state of the AccR transcriptional regulator. Oxidized quinones, e.g., ubiquinone 0 and menadione, switched the AccS′ autokinase activity off, and three conserved Cys residues, which are not essential for catalysis, are involved in such inhibition. Thiol oxidation by quinones caused a change in the oligomeric state of the AccS′ dimer resulting in the formation of an inactive monomer. This thiol-based redox switch is tuned by the cellular energy state, which can change depending on the carbon source that the cells are using. This work expands the functional diversity of redox-sensitive sensor kinases, showing that they can control new bacterial processes such as CCR of the anaerobic catabolism of aromatic compounds. The AccSR two-component system is conserved in the genomes of some betaproteobacteria, where it might play a more general role in controlling the global metabolic state according to carbon availability.IMPORTANCETwo-component signal transduction systems comprise a sensor histidine kinase and its cognate response regulator, and some have evolved to sense and convert redox signals into regulatory outputs that allow bacteria to adapt to the altered redox environment. The work presented here expands knowledge of the functional diversity of redox-sensing kinases to control carbon catabolite repression (CCR), a phenomenon that allows the selective assimilation of a preferred compound among a mixture of several carbon sources. The newly characterized AccS sensor kinase is responsible for the phosphorylation and activation of the AccR master regulator involved in CCR of the anaerobic degradation of aromatic compounds in the betaproteobacteriumAzoarcussp. CIB. AccS seems to have a thiol-based redox switch that is modulated by the redox state of the quinone pool. The AccSR system is conserved in several betaproteobacteria, where it might play a more general role controlling their global metabolic state.

scholarly journals Hik36–Hik43 and Rre6 act as a two-component regulatory system to control cell aggregation in Synechocystis sp. PCC6803

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kota Kera ◽  
Yuichiro Yoshizawa ◽  
Takehiro Shigehara ◽  
Tatsuya Nagayama ◽  
Masaru Tsujii ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Morphological Changes ◽  
Response Regulator ◽  
Control Cell ◽  
Regulatory System ◽  
Cell Aggregation ◽  
Wild Type ◽  
Type Iv ◽  
Two Component ◽  
In The Wild

Abstract In response to environmental stress the model cyanobacterium, Synechocystis sp. PCC6803 can switch from a planktonic state to autoaggregation and biofilm formation. The precise mechanism of this transition remains unknown. Here we investigated the role of a candidate two-component regulatory system (TCS) in controlling morphological changes, as a way to understand the intermediate molecular steps that are part of the signaling pathway. A bacterial two-hybrid assay showed that the response regulator Rre6 formed a TCS together with a split histidine kinase consisting of Hik36 and Hik43. Individual disruption mutants displayed autoaggregation in a static culture. In contrast, unlike in the wild type, high salinity did not induce biofilm formation in Δhik36, Δhik43 and Δrre6. The expression levels of exopolysaccharide (EPS) production genes were higher in Δhik36 and Δhik43, compared with the wild type, but lower in Δrre6, suggesting that the TCS regulated EPS production in Synechocystis. Rre6 interacted physically with the motor protein PilT2, that is a component of the type IV pilus system. This interaction was enhanced in a phosphomimic version of Rre6. Taken together, Hik36–Hik43–Rre6 function as an upstream component of the pili-related signal transduction cascade and control the prevention of cell adhesion and biofilm formation.

scholarly journals Autoinducer-2 and QseC Control Biofilm Formation and In Vivo Virulence of Aggregatibacter actinomycetemcomitans

2010 ◽  
Vol 78 (7) ◽  
pp. 2919-2926 ◽  
Author(s):  
Elizabeth A. Novak ◽  
HanJuan Shao ◽  
Carlo Amorin Daep ◽  
Donald R. Demuth
Keyword(s):  
Bone Resorption ◽  
Bone Loss ◽  
Biofilm Formation ◽  
Alveolar Bone ◽  
Wild Type ◽  
Two Component System ◽  
Component System ◽  
Autoinducer 2 ◽  
Two Component

ABSTRACT Biofilm formation by the periodontal pathogen Aggregatibacter actinomycetemcomitans is dependent upon autoinducer-2 (AI-2)-mediated quorum sensing. However, the components that link the detection of the AI-2 signal to downstream gene expression have not been determined. One potential regulator is the QseBC two-component system, which is part of the AI-2-dependent response pathway that controls biofilm formation in Escherichia coli. Here we show that the expression of QseBC in A. actinomycetemcomitans is induced by AI-2 and that induction requires the AI-2 receptors, LsrB and/or RbsB. Additionally, inactivation of qseC resulted in reduced biofilm growth. Since the ability to grow in biofilms is essential for A. actinomycetemcomitans virulence, strains that were deficient in QseC or the AI-2 receptors were examined in an in vivo mouse model of periodontitis. The ΔqseC mutant induced significantly less alveolar bone resorption than the wild-type strain (P < 0.02). Bone loss in animals infected with the ΔqseC strain was similar to that in sham-infected animals. The ΔlsrB, ΔrbsB, and ΔlsrB ΔrbsB strains also induced significantly less alveolar bone resorption than the wild type (P < 0.03, P < 0.02, and P < 0.01, respectively). However, bone loss induced by a ΔluxS strain was indistinguishable from that induced by the wild type, suggesting that AI-2 produced by indigenous microflora in the murine oral cavity may complement the ΔluxS mutation. Together, these results suggest that the QseBC two-component system is part of the AI-2 regulon and may link the detection of AI-2 to the regulation of downstream cellular processes that are involved in biofilm formation and virulence of A. actinomycetemcomitans.

scholarly journals Quantitative Kinetic Analyses of Shutting Off a Two-Component System

mBio ◽  
2017 ◽  
Vol 8 (3) ◽  
Author(s):  
Rong Gao ◽  
Ann M. Stock
Keyword(s):  
Phosphatase Activity ◽  
Response Regulator ◽  
Two Component System ◽  
Component System ◽  
Signaling Systems ◽  
Cellular Environment ◽  
Two Component ◽  
The Impact

ABSTRACT Cells rely on accurate control of signaling systems to adapt to environmental perturbations. System deactivation upon stimulus removal is as important as activation of signaling pathways. The two-component system (TCS) is one of the major bacterial signaling schemes. In many TCSs, phosphatase activity of the histidine kinase (HK) is believed to play an essential role in shutting off the pathway and resetting the system to the prestimulus state. Two basic challenges are to understand the dynamic behavior of system deactivation and to quantitatively evaluate the role of phosphatase activity under natural cellular conditions. Here we report a kinetic analysis of the response to shutting off the archetype Escherichia coli PhoR-PhoB TCS pathway using both transcription reporter assays and in vivo phosphorylation analyses. Upon removal of the stimulus, the pathway is shut off by rapid dephosphorylation of the PhoB response regulator (RR) while PhoB-regulated gene products gradually reset to prestimulus levels through growth dilution. We developed an approach combining experimentation and modeling to assess in vivo kinetic parameters of the phosphatase activity with kinetic data from multiple phosphatase-diminished mutants. This enabled an estimation of the PhoR phosphatase activity in vivo , which is much stronger than the phosphatase activity of PhoR cytoplasmic domains analyzed in vitro . We quantitatively modeled how strong the phosphatase activity needs to be to suppress nonspecific phosphorylation in TCSs and discovered that strong phosphatase activity of PhoR is required for cross-phosphorylation suppression. IMPORTANCE Activation of TCSs has been extensively studied; however, the kinetics of shutting off TCS pathways is not well characterized. We present comprehensive analyses of the shutoff response for the PhoR-PhoB system that reveal the impact of phosphatase activity on shutoff kinetics. This allows development of a quantitative framework not only to characterize the phosphatase activity in the natural cellular environment but also to understand the requirement for specific strengths of phosphatase activity to suppress nonspecific phosphorylation. Our model suggests that the ratio of the phosphatase rate to the nonspecific phosphorylation rate correlates with TCS expression levels and the ratio of the RR to HK, which may contribute to the great diversity of enzyme levels and activities observed in different TCSs.

scholarly journals LuxS-Mediated Signaling in Streptococcus mutans Is Involved in Regulation of Acid and Oxidative Stress Tolerance and Biofilm Formation

2004 ◽  
Vol 186 (9) ◽  
pp. 2682-2691 ◽  
Author(s):  
Zezhang T. Wen ◽  
Robert A. Burne
Keyword(s):  
Streptococcus Mutans ◽  
Response Regulator ◽  
Regulatory Protein ◽  
Protein A ◽  
Signal Recognition Particle ◽  
Northern Hybridization ◽  
Wild Type ◽  
Increased Sensitivity ◽  
Mutant Phenotypes ◽  
Almost All

ABSTRACT LuxS-mediated quorum sensing has recently been shown to regulate important physiologic functions and virulence in a variety of bacteria. In this study, the role of luxS of Streptococcus mutans in the regulation of traits crucial to pathogenesis was investigated. Reporter gene fusions showed that inactivation of luxS resulted in a down-regulation of fructanase, a demonstrated virulence determinant, by more than 50%. The LuxS-deficient strain (TW26) showed increased sensitivity to acid killing but could still undergo acid adaptation. Northern hybridization revealed that the expression of RecA, SmnA (AP endonuclease), and Nth (endonuclease) were down-regulated in TW26, especially in early-exponential-phase cells. Other down-regulated genes included ffh (a signal recognition particle subunit) and brpA (biofilm regulatory protein A). Interestingly, the luxS mutant showed an increase in survival rate in the presence of hydrogen peroxide (58.8 mM). The luxS mutant formed less biofilm on hydroxylapatite disks, especially when grown in biofilm medium with sucrose, and the mutant biofilms appeared loose and hive-like, whereas the biofilms of the wild type were smooth and confluent. The mutant phenotypes were complemented by exposure to supernatants from wild-type cultures. Two loci, smu486 and smu487, were identified and predicted to encode a histidine kinase and a response regulator. The phenotypes of the smu486 smu487 mutant were, in almost all cases, similar to those of the luxS mutant, although our results suggest that this is not due to AI-2 signal transduction via Smu486 and Smu487. This study demonstrates that luxS-dependent signaling plays critical roles in modulating key virulence properties of S. mutans.

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