scholarly journals A Sensor of the Two-Component System CpxA Affects Expression of the Type III Secretion System through Posttranscriptional Processing of InvE

2005 ◽  
Vol 187 (1) ◽  
pp. 107-113 ◽  
Author(s):  
Jiro Mitobe ◽  
Eiji Arakawa ◽  
Haruo Watanabe
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Deletion Strain ◽  
Activity Levels ◽  
Galactosidase Activity ◽  
Two Component System ◽  
Component System ◽  
Two Component ◽  
Posttranscriptional Processing

ABSTRACT The chief function of the Cpx two-component system is perceiving various cell envelope stresses, but CpxR is also known to regulate the expression of the type III secretion system (TTSS) of Shigella sonnei through transcription of the primary regulator virF. Here, we have isolated novel cpxA mutants that exhibited decreased TTSS expression from Escherichia coli HW1273, which carries the virulence plasmid of S. sonnei. The cpxA deletion strain of HW1273 expressed β-galactosidase activity levels from the virF-lacZ fusion similar to those of HW1273. However, the second regulator InvE (VirB) and the TTSS component IpaB proteins were apparently expressed at a low level. In the cpxA strain, β-galactosidase activity levels from the invE-lacZ transcriptional fusion remained similar to those of HW1273, whereas the β-galactosidase activity level from the translational fusion of invE-lacZ was reduced to 21% of that of HW1273. Therefore, the deletion of the cpxA gene influenced TTSS expression chiefly at the posttranscriptional processing of InvE. In addition, the cpxA deletion strain of S. sonnei showed the same phenotype. These results indicate that the Cpx two-component system is involved in virulence expression through posttranscriptional processing of the regulatory protein InvE, a novel feature of the Cpx two-component system in posttranscriptional processing and virulence expression of Shigella.

scholarly journals Two-Component Sensor RhpS Promotes Induction of Pseudomonas syringae Type III Secretion System by Repressing Negative Regulator RhpR

2007 ◽  
Vol 20 (3) ◽  
pp. 223-234 ◽  
Author(s):  
Yanmei Xiao ◽  
Lefu Lan ◽  
Chuntao Yin ◽  
Xin Deng ◽  
Douglas Baker ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Strain ◽  
Wild Type Strain ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Deletion Strain ◽  
Wild Type ◽  
Two Component ◽  
In The Wild

The Pseudomonas syringae type III secretion system (T3SS) is induced during interaction with the plant or culture in minimal medium (MM). How the bacterium senses these environments to activate the T3SS is poorly understood. Here, we report the identification of a novel two-component system (TCS), RhpRS, that regulates the induction of P. syringae T3SS genes. The rhpR and rhpS genes are organized in an operon with rhpR encoding a putative TCS response regulator and rhpS encoding a putative biphasic sensor kinase. Transposon insertion in rhpS severely reduced the induction of P. syringae T3SS genes in the plant as well as in MM and significantly compromised the pathogenicity on host plants and hypersensitive response-inducing activity on nonhost plants. However, deletion of the rhpRS locus allowed the induction of T3SS genes to the same level as in the wild-type strain and the recovery of pathogenicity upon infiltration into plants. Overexpression of RhpR in the ΔrhpRS deletion strain abolished the induction of T3SS genes. However, overexpression of RhpR in the wild-type strain or overexpression of RhpR(D70A), a mutant of the predicted phosphorylation site of RhpR, in the ΔrhpRS deletion strain only slightly reduced the induction of T3SS genes. Based on these results, we propose that the phosphorylated RhpR represses the induction of T3SS genes and that RhpS reverses phosphorylation of RhpR under the T3SS-inducing conditions. Epistasis analysis indicated that rhpS and rhpR act upstream of hrpR to regulate T3SS genes.

scholarly journals Signal Pathway in Salt-Activated Expression of the Salmonella Pathogenicity Island 1 Type III Secretion System in Salmonella enterica Serovar Typhimurium

2008 ◽  
Vol 190 (13) ◽  
pp. 4624-4631 ◽  
Author(s):  
Hideaki Mizusaki ◽  
Akiko Takaya ◽  
Tomoko Yamamoto ◽  
Shin-Ichi Aizawa
Keyword(s):  
Electron Microscopy ◽  
Real Time ◽  
Protein Secretion ◽  
Real Time Pcr ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Sds Page ◽  
Two Component ◽  
Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium secretes virulence factors for invasion called Sip proteins or Sips into its hosts through a type III secretion system (T3SS). In the absence of a host, S. enterica induces Sip secretion in response to sucrose or simple salts, such as NaCl. We analyzed induction of host-independent Sip secretion by monitoring protein secretion by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), assembly of needle complexes by electron microscopy, and transcription of virulence regulatory genes by quantitative reverse transcriptase PCR (real-time PCR). SDS-PAGE showed that addition of sucrose or simple salts, such as NaCl, to the growth medium induced Sip secretion without altering flagellar protein secretion, which requires a distinct T3SS. Electron microscopy confirmed that the amount of secreted Sips increased as the number of assembled needle complexes increased. Real-time PCR revealed that added sucrose or NaCl enhanced transcription of hilA, hilC, and hilD, which encode known regulators of Salmonella virulence. However, epistasis analysis implicated HilD and HilA, but not HilC, in the direct pathway from the salt stimulus to the Sip secretion response. Further analyses showed that the BarA/SirA two-component signal transduction pathway, but not the two-component sensor kinase EnvZ, directly activated hilD and hilA transcription and thus Sip secretion in response to either sucrose or NaCl. Finally, real-time PCR showed that salt does not influence transcription of the BarA/SirA-dependent csrB and csrC genes. A model is proposed for the major pathway in which sucrose or salt signals to enhance virulence gene expression.

scholarly journals Differential Accumulation of Form I RubisCO in Rhodopseudomonas palustris CGA010 under Photoheterotrophic Growth Conditions with Reduced Carbon Sources

2009 ◽  
Vol 191 (13) ◽  
pp. 4243-4250 ◽  
Author(s):  
Gauri S. Joshi ◽  
Simona Romagnoli ◽  
Nathan C. VerBerkmoes ◽  
Robert L. Hettich ◽  
Dale Pelletier ◽  
...  
Keyword(s):  
Purple Bacteria ◽  
Rhodopseudomonas Palustris ◽  
Growth Conditions ◽  
Activity Levels ◽  
Two Component System ◽  
Rubisco Activity ◽  
Bisphosphate Carboxylase ◽  
Component System ◽  
Two Component ◽  
Photoheterotrophic Growth

ABSTRACT Rhodopseudomonas palustris is unique among characterized nonsulfur purple bacteria because of its capacity for anaerobic photoheterotrophic growth using aromatic acids. Like growth with other reduced electron donors, this growth typically requires the presence of bicarbonate/CO2 or some other added electron acceptor in the growth medium. Proteomic studies indicated that there was specific accumulation of form I ribulose 1, 5-bisphosphate carboxylase/oxygenase (RubisCO) subunit proteins (CbbL and CbbS), as well as the CbbX protein, in cells grown on benzoate without added bicarbonate; such cells used the small amounts of dissolved CO2 in the medium to support growth. These proteins were not observed in extracts from cells grown in the presence of high levels (10 mM) of added bicarbonate. To confirm the results of the proteomics studies, it was shown that the total RubisCO activity levels were significantly higher (five- to sevenfold higher) in wild-type (CGA010) cells grown on benzoate with a low level (0.5 mM) of added bicarbonate. Immunoblots indicated that the increase in RubisCO activity levels was due to a specific increase in the amount of form I RubisCO (CbbLS) and not in the amount of form II RubisCO (CbbM), which was constitutively expressed. Deletion of the main transcriptional regulator gene, cbbR, resulted in impaired growth on benzoate-containing low-bicarbonate media, and it was established that form I RubisCO synthesis was absolutely and specifically dependent on CbbR. To understand the regulatory role of the CbbRRS two-component system, strains with nonpolar deletions of the cbbRRS genes were grown on benzoate. Distinct from the results obtained with photoautotrophic growth conditions, the results of studies with various CbbRRS mutant strains indicated that this two-component system did not affect the observed enhanced synthesis of form I RubisCO under benzoate growth conditions. These studies indicate that diverse growth conditions differentially affect the ability of the CbbRRS two-component system to influence cbb transcription.

scholarly journals OmpR Regulates the Two-Component System SsrA-SsrB in Salmonella Pathogenicity Island 2

2000 ◽  
Vol 182 (3) ◽  
pp. 771-781 ◽  
Author(s):  
Anthea K. Lee ◽  
Corrella S. Detweiler ◽  
Stanley Falkow
Keyword(s):  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Regulatory System ◽  
Systemic Infection ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Host Cells ◽  
Type Iii ◽  
Two Component ◽  
Footprint Analysis

ABSTRACT Salmonella pathogenicity island 2 (SPI-2) encodes a putative, two-component regulatory system, SsrA-SsrB, which regulates a type III secretion system needed for replication inside macrophages and systemic infection in mice. The sensor and regulator homologs,ssrAB (spiR), and genes within the secretion system, including the structural gene ssaH, are transcribed after Salmonella enters host cells. We have studied the transcriptional regulation of ssrAB and the secretion system by using gfp fusions to the ssrA andssaH promoters. We found that early transcription ofssrA, after entry into macrophages, is most efficient in the presence of OmpR. An ompR mutant strain does not exhibit replication within cultured macrophages. Furthermore, footprint analysis shows that purified OmpR protein binds directly to thessrA promoter region. We also show that minimal medium, pH 4.5, induces SPI-2 gene expression in wild-type but notompR mutant strains. We conclude that the type III secretion system of SPI-2 is regulated by OmpR, which activates expression of ssrA soon after Salmonella enters the macrophage.

scholarly journals Carbon starvation induces the expression of PprB-regulated genes inPesudomonas aeruginosa

2019 ◽  
Author(s):  
Congcong Wang ◽  
Wenhui Chen ◽  
Aiguo Xia ◽  
Rongrong Zhang ◽  
Yajia Huang ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Surface ◽  
Biofilm Formation ◽  
Carbon Starvation ◽  
Secretion System ◽  
Starvation Stress ◽  
Two Component System ◽  
Component System ◽  
Two Component ◽  
Cell Cell

ABSTRACTPseudomonas aeruginosacan cause severe infections in humans. This bacteria often adopt a biofilm lifestyle that is hard to treat. In several previous studies, the PprA-PprB two-component system (TCS), which controls the expression of type IVb pili, BapA adhesin, and CupE fimbriae, was shown to be involved in biofilm formation. However, signals or environmental conditions that can trigger the PprA-PprB TCS are still unknown, and the molecular mechanisms of PprB-mediated biofilm formation are poorly characterized. Here we report that carbon starvation stress (CCS) can induce the expression ofpprBand genes in the PprB regulon. The stress response sigma factor RpoS, rather than the two-component sensor PprA, was determined to mediate the induction ofpprBtranscription. We also observed a strong negative regulation of PprB to the transcription of itself. Further experiments showed that PprB overexpression greatly enhanced cell-cell adhesion (CCA) and cell-surface adhesion (CSA) inP. aeruginosa. Specially, under the background of PprB overexpression, both of the BapA adhesin and CupE fimbriae displayed positive effect on CCA and CSA, while the type IVb pili showed an unexpected negative effect on CCA and no effect on CSA. In addition, expression of the PprB regulon genes displayed significant increases in 3-day colony biofilms, indicating a possible carbon limitation state in these biofilms. The CSS-RpoS-PprB-Bap/Flp/CupE/Tad pathway identified in this study provides a new perspective on the process of biofilm formation under carbon-limited environments.IMPORTANCETypically, determining the external signals that can trigger a regulatory system is crucial to understand the regulatory logic and inward function of that system. The PprA-PprB two-component system was reported to be involved in biofilm formation inPseudomonas aeruginosa, but the signals that can trigger this system are unknown. In this study, we found that carbon starvation stress (CSS) can induce the transcription ofpprBand genes in PprB regulon, through an RpoS dependent pathway. Increase of PprB expression leads to enhanced cell-cell and cell-surface adhesions inP. aeruginosa,both of which are dependent mainly on the Bap adhesin secretion system and partially on the CupE fimbriae. Our findings suggest that PprB reinforces the structure of biofilms under carbon-limited conditions, and the Bap secretion system and CupE fimbriae are two potential targets for biofilm treatment.

scholarly journals Transcription of the SsrAB Regulon Is Repressed by Alkaline pH and Is Independent of PhoPQ and Magnesium Concentration

2002 ◽  
Vol 184 (5) ◽  
pp. 1493-1497 ◽  
Author(s):  
Edward A. Miao ◽  
Jeremy A. Freeman ◽  
Samuel I. Miller
Keyword(s):  
Type Iii Secretion ◽  
Regulatory System ◽  
Secretion System ◽  
Effector Proteins ◽  
Magnesium Concentration ◽  
Intracellular Bacteria ◽  
Alkaline Ph ◽  
Two Component System ◽  
Two Component ◽  
Serovar Typhimurium

ABSTRACT The Salmonella pathogenicity island 2 (SPI-2) type III secretion system is expressed by intracellular bacteria and translocates effector proteins across the vacuolar membrane. Signals sensed by Salmonella enterica serovar Typhimurium in the intracellular compartment activate SPI-2 gene expression through the two-component regulatory system SsrAB. The effects of environmental and genetic signals on expression of the SsrAB-regulated gene sspH2 were examined. SsrAB-dependent activation of sspH2 was detected in the presence of both low and moderate concentrations of magnesium or calcium and at acidic and neutral pHs. The levels of expression were comparable to those detected in bacteria recovered from cultured macrophages. The induction in media at alkaline pHs (pH 7.5 and 8.0) was greatly reduced compared to the induction observed at pH 7.0 or at a lower pH, suggesting that alkaline pH represses SsrAB activation. In addition, the PhoPQ two-component system, which is also activated intracellularly, was not required for activation of SsrAB.

Sign in / Sign up

Export Citation Format

Share Document