scholarly journals ExoS/ChvI Two-Component Signal-Transduction System Activated in the Absence of Bacterial Phosphatidylcholine

2021 ◽  
Vol 12 ◽  
Author(s):  
Otto Geiger ◽  
Christian Sohlenkamp ◽  
Diana Vera-Cruz ◽  
Daniela B. Medeot ◽  
Lourdes Martínez-Aguilar ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Regulatory System ◽  
Deficient Mutant ◽  
Wild Type ◽  
Membrane Phospholipids ◽  
Two Component System ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Suppressor Mutants ◽  
Transcript Profiles

Sinorhizobium meliloti contains the negatively charged phosphatidylglycerol and cardiolipin as well as the zwitterionic phosphatidylethanolamine (PE) and phosphatidylcholine (PC) as major membrane phospholipids. In previous studies we had isolated S. meliloti mutants that lack PE or PC. Although mutants deficient in PE are able to form nitrogen-fixing nodules on alfalfa host plants, mutants lacking PC cannot sustain development of any nodules on host roots. Transcript profiles of mutants unable to form PE or PC are distinct; they differ from each other and they are different from the wild type profile. For example, a PC-deficient mutant of S. meliloti shows an increase of transcripts that encode enzymes required for succinoglycan biosynthesis and a decrease of transcripts required for flagellum formation. Indeed, a PC-deficient mutant is unable to swim and overproduces succinoglycan. Some suppressor mutants, that regain swimming and form normal levels of succinoglycan, are altered in the ExoS sensor. Our findings suggest that the lack of PC in the sinorhizobial membrane activates the ExoS/ChvI two-component regulatory system. ExoS/ChvI constitute a molecular switch in S. meliloti for changing from a free-living to a symbiotic life style. The periplasmic repressor protein ExoR controls ExoS/ChvI function and it is thought that proteolytic ExoR degradation would relieve repression of ExoS/ChvI thereby switching on this system. However, as ExoR levels are similar in wild type, PC-deficient mutant and suppressor mutants, we propose that lack of PC in the bacterial membrane provokes directly a conformational change of the ExoS sensor and thereby activation of the ExoS/ChvI two-component system.

scholarly journals Regulation of Virulence by a Two-Component System in Group B Streptococcus

2005 ◽  
Vol 187 (3) ◽  
pp. 1105-1113 ◽  
Author(s):  
Sheng-Mei Jiang ◽  
Michael J. Cieslewicz ◽  
Dennis L. Kasper ◽  
Michael R. Wessels
Keyword(s):  
Response Regulator ◽  
Newborn Infants ◽  
Regulatory System ◽  
Virulence Determinants ◽  
Wild Type ◽  
Two Component System ◽  
Component System ◽  
Two Component ◽  
Mutant Strains ◽  
Group B

ABSTRACT Group B Streptococcus (GBS) is frequently carried in the gastrointestinal or genitourinary tract as a commensal organism, yet it has the potential to cause life-threatening infection in newborn infants, pregnant women, and individuals with chronic illness. Regulation of virulence factor expression may affect whether GBS behaves as an asymptomatic colonizer or an invasive pathogen, but little is known about how such factors are controlled in GBS. We now report the characterization of a GBS locus that encodes a two-component regulatory system similar to CsrRS (or CovRS) in Streptococcus pyogenes. Inactivation of csrR, encoding the putative response regulator, in two unrelated wild-type strains of GBS resulted in a marked increase in production of beta-hemolysin/cytolysin and a striking decrease in production of CAMP factor, an unrelated cytolytic toxin. Quantitative RNA hybridization experiments revealed that these two phenotypes were associated with a marked increase and decrease in expression of the corresponding genes, cylE and cfb, respectively. The CsrR mutant strains also displayed increased expression of scpB encoding C5a peptidase. Similar, but less marked, changes in gene expression were observed in CsrS (putative sensor component) mutants, evidence that CsrR and CsrS constitute a functional two-component system. Experimental infection studies in mice demonstrated reduced virulence of both CsrR and CsrS mutant strains relative to the wild type. Together, these results indicate that CsrRS regulates expression of multiple GBS virulence determinants and is likely to play an important role in GBS pathogenesis.

scholarly journals Sinorhizobium meliloti SyrA Mediates the Transcriptional Regulation of Genes Involved in Lipopolysaccharide Sulfation and Exopolysaccharide Biosynthesis

2007 ◽  
Vol 189 (6) ◽  
pp. 2510-2520 ◽  
Author(s):  
David H. Keating
Keyword(s):  
Sinorhizobium Meliloti ◽  
Response Regulator ◽  
Living Conditions ◽  
Wild Type ◽  
Two Component System ◽  
Free Living ◽  
Component System ◽  
Two Component ◽  
Exopolysaccharide Biosynthesis ◽  
Free Living Conditions

ABSTRACT Sinorhizobium meliloti is a gram-negative soil bacterium found either in free-living form or as a nitrogen-fixing endosymbiont of leguminous plants such as Medicago sativa (alfalfa). S. meliloti synthesizes an unusual sulfate-modified form of lipopolysaccharide (LPS). A recent study reported the identification of a gene, lpsS, which encodes an LPS sulfotransferase activity in S. meliloti. Mutants bearing a disrupted version of lpsS exhibit an altered symbiosis, in that they elicit more nodules than wild type. However, under free-living conditions, the lpsS mutant displayed no change in LPS sulfation. These data suggest that the expression of lpsS is differentially regulated, such that it is transcriptionally repressed during free-living conditions but upregulated during symbiosis. Here, I show that the expression of lpsS is upregulated in strains that constitutively express the symbiotic regulator SyrA. SyrA is a small protein that lacks an apparent DNA binding domain and is predicted to be located in the cytoplasmic membrane yet is sufficient to upregulate lpsS transcription. Furthermore, SyrA can mediate the transcriptional upregulation of exo genes involved in the biosynthesis of the symbiotic exopolysaccharide succinoglycan. The SyrA-mediated transcriptional upregulation of lpsS and exo transcription is blocked in mutants harboring a mutation in chvI, which encodes the response regulator of a conserved two-component system. Thus, SyrA likely acts indirectly to promote transcriptional upregulation of lpsS and exo genes through a mechanism that requires the ExoS/ChvI two-component system.

scholarly journals Two-Component Signal Transduction System VraSR Contributes to Neuroinflammation in Streptococcus Suis Meningitis

2021 ◽  
Author(s):  
Beibei Dou ◽  
Xia Yang ◽  
Fengming Yang ◽  
Kang Yan ◽  
Wei Peng ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Proinflammatory Cytokines ◽  
Regulatory System ◽  
Streptococcus Suis ◽  
Wild Type ◽  
Signal Transduction System ◽  
Cytokines And Chemokines ◽  
Two Component ◽  
Two Component Signal Transduction

Abstract Background: Streptococcus suis (S. suis) is an important zoonotic pathogen that can cause high morbidity and mortality in both humans and swine. As the most important life-threatening infection of the central nervous system (CNS), meningitis is an important symptom of S. suis infection. The VraSR is a critical two-component signal transduction system that affects S. suis ability to resist against host innate immune system and promotes the ability of S. suis to adhere to hBMEC. Whether and how VraSR contributes to the development of S. suis meningitis are currently unknown.Methods: The in vivo colonization, in vivo BBB permeability, histopathological examination and immunohistochemistry were applied to compare and characterize the degree of destruction of brain tissue in response to wild type SC19 and mutant ΔvraSR. Western blotting and real-time PCR were combined to identify the breakdown of tight junction proteins (TJ proteins). The secretion of proinflammatory cytokines and chemokines in the serum were detected on a BD FACSVerse flow cytometer.Results: We found an important role of VraSR regulatory system in S. suis SC19-induced meningitis. A mouse infection model demonstrated that ΔvraSR had significantly attenuated inflammatory lesions in the brain tissues compared with wild-type S. suis. In vitro, we characterized that SC19 could increase the blood-brain barrier (BBB) permeability through downregulating the TJ proteins compared with mutant ΔvraSR. Moreover, we found significant generation of proinflammatory cytokines and chemokines in the serum including IL-6, TNF-α, MCP-1, and IL-12p70 compared with ΔvraSR infected mice.Conclusions: For the first time, our work investigated the VraSR regulatory system of S. suis played an important role in streptococcal meningitis and revealed VraSR to be an important contributor to the disruption of TJ proteins. Characterization of these BBB disruption will facilitate further study of meningitis mechanisms in humans, thereby offering the development of novel preventative and therapeutic strategies against infection with S. suis.

The two-component system ActJK is involved in acid stress tolerance and symbiosis in Sinorhizobium meliloti

2021 ◽  
Vol 329 ◽  
pp. 80-91
Author(s):  
Francisco J. Albicoro ◽  
Walter O. Draghi ◽  
María C. Martini ◽  
María E. Salas ◽  
G.A. Torres Tejerizo ◽  
...  
Keyword(s):  
Stress Tolerance ◽  
Sinorhizobium Meliloti ◽  
Acid Stress ◽  
Two Component System ◽  
Component System ◽  
Two Component

scholarly journals The Two-Component Regulatory System TCS08 Is Involved in Cellobiose Metabolism of Streptococcus pneumoniae R6

2006 ◽  
Vol 189 (4) ◽  
pp. 1342-1350 ◽  
Author(s):  
Stuart J. McKessar ◽  
Regine Hakenbeck
Keyword(s):  
Streptococcus Pneumoniae ◽  
Response Regulator ◽  
Regulatory System ◽  
Phosphotransferase System ◽  
Two Component System ◽  
Transcription Profiles ◽  
Regulatory Systems ◽  
Two Component ◽  
Cognate Response Regulator ◽  
Gram Positive Cocci

ABSTRACT The two-component system TCS08 is one of the regulatory systems that is important for virulence of Streptococcus pneumoniae. In order to investigate the TCS08 regulon, we have analyzed transcription profiles of mutants derived from S. pneumoniae R6 by microarray analysis. Since deletion mutants are often without a significant phenotype, we constructed a mutation in the histidine kinase HK08, T133P, in analogy to the phosphatase mutation T230P in the H box of the S. pneumoniae CiaH kinase described recently (D. Zähner, K. Kaminski, M. van der Linden, T. Mascher, M. Merai, and R. Hakenbeck, J. Mol. Microbiol. Biotechnol. 4:211-216, 2002). In addition, a deletion mutation was constructed in rr08, encoding the cognate response regulator. The most heavily suppressed genes in the hk08 mutant were spr0276 to spr0282, encoding a putative cellobiose phosphoenolpyruvate sugar phosphotransferase system (PTS). Whereas the R6 Smr parent strain and the Δrr08 mutant readily grew on cellobiose, the hk08 mutant and selected mutants with deletions in the PTS cluster did not, strongly suggesting that TCS08 is involved in the catabolism of cellobiose. Homologues of the TCS08 system were found in closely related streptococci and other gram-positive cocci. However, the genes spr0276 to spr0282, encoding the putative cellobiose PTS, represent a genomic island in S. pneumoniae and homologues were found in Streptococcus gordonii only, suggesting that this system might contribute to the pathogenicity potential of the pneumococcus.

scholarly journals Identification of a Second Two-Component Signal Transduction System That Controls Fosfomycin Tolerance and Glycerol-3-Phosphate Uptake

2014 ◽  
Vol 197 (5) ◽  
pp. 861-871 ◽  
Author(s):  
Kumiko Kurabayashi ◽  
Yuko Hirakawa ◽  
Koichi Tanimoto ◽  
Haruyoshi Tomita ◽  
Hidetada Hirakawa
Keyword(s):  
Phosphate Uptake ◽  
Response Regulator ◽  
Anaerobic Respiration ◽  
Regulatory System ◽  
Carbon Substrate ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Biological Cost

Particular interest in fosfomycin has resurfaced because it is a highly beneficial antibiotic for the treatment of refractory infectious diseases caused by pathogens that are resistant to other commonly used antibiotics. The biological cost to cells of resistance to fosfomycin because of chromosomal mutation is high. We previously found that a bacterial two-component system, CpxAR, induces fosfomycin tolerance in enterohemorrhagicEscherichia coli(EHEC) O157:H7. This mechanism does not rely on irreversible genetic modification and allows EHEC to relieve the fitness burden that results from fosfomycin resistance in the absence of fosfomycin. Here we show that another two-component system, TorSRT, which was originally characterized as a regulatory system for anaerobic respiration utilizing trimethylamine-N-oxide (TMAO), also induces fosfomycin tolerance. Activation of the Tor regulatory pathway by overexpression oftorR, which encodes the response regulator, or addition of TMAO increased fosfomycin tolerance in EHEC. We also show that phosphorylated TorR directly represses the expression ofglpT, a gene that encodes a symporter of fosfomycin and glycerol-3-phosphate, and activation of the TorR protein results in the reduced uptake of fosfomycin by cells. However, cells in which the Tor pathway was activated had an impaired growth phenotype when cultured with glycerol-3-phosphate as a carbon substrate. These observations suggest that the TorSRT pathway is the second two-component system to reversibly control fosfomycin tolerance and glycerol-3-phosphate uptake in EHEC, and this may be beneficial for bacteria by alleviating the biological cost. We expect that this mechanism could be a potential target to enhance the utility of fosfomycin as chemotherapy against multidrug-resistant pathogens.

scholarly journals Enhancement of Glutamine Utilization in Bacillus subtilis through the GlnK-GlnL Two-Component Regulatory System

2005 ◽  
Vol 187 (14) ◽  
pp. 4813-4821 ◽  
Author(s):  
Takenori Satomura ◽  
Daisuke Shimura ◽  
Kei Asai ◽  
Yoshito Sadaie ◽  
Kazutake Hirooka ◽  
...  
Keyword(s):  
Transcription Initiation ◽  
Culture Medium ◽  
Regulatory System ◽  
Direct Repeat ◽  
Northern Analysis ◽  
Two Component System ◽  
Dnase I Footprinting ◽  
Glutamine Transporter ◽  
Two Component ◽  
Extension Analysis

ABSTRACT During DNA microarray analysis, we discovered that the GlnK-GlnL (formerly YcbA-YcbB) two-component system positively regulates the expression of the glsA-glnT (formerly ybgJ-ybgH) operon in response to glutamine in the culture medium on Northern analysis. As a result of gel retardation and DNase I footprinting analyses, we found that the GlnL protein interacts with a region (bases −13 to −56; +1 is the transcription initiation base determined on primer extension analysis of glsA-glnT) in which a direct repeat, TTTTGTN4TTTTGT, is present. Furthermore, the glsA and glnT genes were biochemically verified to encode glutaminase and glutamine transporter, respectively.

scholarly journals The Basis of Ammonium Release in nifLMutants of Azotobacter vinelandii

1999 ◽  
Vol 181 (23) ◽  
pp. 7356-7362 ◽  
Author(s):  
Brett Brewin ◽  
Paul Woodley ◽  
Martin Drummond
Keyword(s):  
Azotobacter Vinelandii ◽  
Transcriptional Level ◽  
Uptake System ◽  
Wild Type ◽  
Two Component System ◽  
Two Component ◽  
In The Wild ◽  
Reducing Activity ◽  
State Growth ◽  
Acetylene Reducing Activity

ABSTRACT In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations innifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator ofnif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium release. Enhancement of NifA-mediated transcription, on the other hand, by either elimination ofnifL or overexpression of nifA, resulted in ammonium release, correlating with enhanced levels of nifHmRNA, raised levels of nitrogenase and acetylene-reducing activity, and increased concentrations of intracellular ammonium. Up to 35 mM ammonium can accumulate in the medium. Where measured, intracellular levels exceeded extracellular levels, indicating that rather than being actively transported, ammonium is lost from the cell passively, possibly by reversal of an NH4 + uptake system. The data also indicate that in the wild type the bulk of NifA is inactivated by NifL during steady-state growth on dinitrogen.

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.

alr0117, a two-component histidine kinase gene, is involved in heterocyst development in Anabaena sp. PCC 7120

Microbiology ◽  
2004 ◽  
Vol 150 (2) ◽  
pp. 447-453 ◽  
Author(s):  
Degang Ning ◽  
Xudong Xu
Keyword(s):  
Histidine Kinase ◽  
Regulatory System ◽  
Gene Encoding ◽  
Kinase Gene ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Anabaena Sp ◽  
Pcc 7120 ◽  
Polysaccharide Layer ◽  
Heterocyst Development

Anabaena sp. PCC 7120 was mutagenized by transposon Tn5-1087b, generating a mutant whose heterocysts lack the envelope polysaccharide layer. The transposon was located between nucleotides 342 and 343 of alr0117, a 918 bp gene encoding a histidine kinase for a two-component regulatory system. Complementation of the mutant with a DNA fragment containing alr0117 and targeted inactivation of the gene confirmed that alr0117 is involved in heterocyst development. RT-PCR showed that alr0117 was constitutively expressed in the presence or absence of a combined-nitrogen source. hepA and patB, the two genes turned on during wild-type heterocyst development, were no longer activated in an alr0117-null mutant. The two-component signal transduction system involving alr0117 may control the formation of the envelope polysaccharide layer and certain late events essential to the function of heterocysts.

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