scholarly journals Transcriptional autoregulation of the RcsCDB phosphorelay system in Salmonella enterica serovar Typhimurium

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3513-3521 ◽  
Author(s):  
María de las Mercedes Pescaretti ◽  
Fabián E. López ◽  
Roberto D. Morero ◽  
Mónica A. Delgado
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Response Regulator ◽  
Physiological Role ◽  
Enteric Bacteria ◽  
System A ◽  
Serovar Typhimurium ◽  
Bacterial Swarming ◽  
Swarming Behaviour

The RcsCDB (Rcs) phosphorelay system is involved in the regulation of many envelope genes, such as those responsible for capsule synthesis, flagella production and O-antigen chain length, as well as in other cellular activities of several enteric bacteria. The system is composed of three proteins: the sensor RcsC, the response regulator RcsB, and the phospho-transfer intermediary protein RcsD. Previously, we reported two important aspects of this system: (a) rcsB gene expression is under the control of P rcsDB and P rcsB promoters, and (b) rcsD gene transcription decreases when the bacteria reach high levels of the RcsB regulator. In the present work, we demonstrate that the RcsB protein represses rcsD gene expression by binding directly to the P rcsDB promoter, negatively autoregulating the Rcs system. Furthermore, we report the physiological role of the RcsB regulator, which is able to modify bacterial swarming behaviour when expressed under the control of the P rcsB promoter.

scholarly journals Role of FimW, FimY, and FimZ in Regulating the Expression of Type I Fimbriae in Salmonella enterica Serovar Typhimurium

2009 ◽  
Vol 191 (9) ◽  
pp. 3003-3010 ◽  
Author(s):  
Supreet Saini ◽  
Jeffrey A. Pearl ◽  
Christopher V. Rao
Keyword(s):  
Gene Expression ◽  
Negative Feedback ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phase Variation ◽  
Type I ◽  
Serovar Typhimurium ◽  
Type I Fimbriae ◽  
Positive And Negative Feedback

ABSTRACT Type I fimbriae in Salmonella enterica serovar Typhimurium are surface appendages that facilitate binding to eukaryotic cells. Expression of the fim gene cluster is known to be regulated by three proteins—FimW, FimY, and FimZ—and a tRNA encoded by fimU. In this work, we investigated how these proteins and tRNA coordinately regulate fim gene expression. Our results indicate that FimY and FimZ independently activate the P fimA promoter which controls the expression of the fim structural genes. FimY and FimZ were also found to strongly activate each other's expression and weakly activate their own expression. FimW was found to negatively regulate fim gene expression by repressing transcription from the P fimY promoter, independent of FimY or FimZ. Moreover, FimW and FimY interact within a negative feedback loop, as FimY was found to activate the P fimW promoter. In the case of fimU, the expression of this gene was not found to be regulated by FimW, FimY, or FimZ. We also explored the effect of fim gene expression on Salmonella pathogenicity island 1 (SPI1). Our results indicate that FimZ alone is able to enhance the expression of hilE, a known repressor of SPI1 gene expression. Based on our results, we were able to propose an integrated model for the fim gene circuit. As this model involves a combination of positive and negative feedback, we hypothesized that the response of this circuit may be bistable and thus a possible mechanism for phase variation. However, we found that the response was continuous and not bistable.

scholarly journals Role of cpxA Mutations in the Resistance to Aminoglycosides and β-Lactams in Salmonella enterica serovar Typhimurium

2021 ◽  
Vol 12 ◽  
Author(s):  
Wenxian Jing ◽  
Juan Liu ◽  
Shanshan Wu ◽  
Xuerui Li ◽  
Yongsheng Liu
Keyword(s):  
Salmonella Enterica ◽  
Deletion Mutant ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Response Regulator ◽  
Deletion Mutants ◽  
Expression Levels ◽  
Serovar Typhimurium ◽  
Regulatory Effects ◽  
A Site

Although it has been reported that deletion of the response regulator, CpxR, in the CpxRA system confers sensitivity to aminoglycosides (AGAs) and β-lactams in Salmonella enterica serovar Typhimurium, the regulatory effects of CpxA on multidrug resistance (MDR) are yet to be fully investigated in this organism. Here, to explore the role of CpxA in MDR, various cpxA mutants including a null mutant (JSΔcpxA), a site-directed mutant (JSΔcpxA38) and an internal in-frame deletion mutant (JSΔcpxA92–104) of the S. enterica serovar Typhimurium strain JS, were constructed. It was revealed that cpxA and cpxR deletion mutants have opposing roles in the regulation of resistance to AGAs and β-lactams. Amikacin and cefuroxime can activate the CpxRA system, which results in increased resistance of the wild-type compared with the cpxR deletion mutant. All the cpxA mutations significantly increased resistance to AGAs and β-lactams due to CpxRA system activation via the phosphorylation of CpxR. Moreover, AckA-Pta-dependent activation of CpxR increased the antibiotic resistance of cpxA deletion mutants. Further research revealed that the AcrAB-TolC conferred resistance to some AGAs and β-lactams but does not influence the regulation of resistance by CpxRA against these antibiotics. The detection of candidate MDR-related CpxR regulons revealed that the mRNA expression levels of spy, ycca, ppia, htpX, stm3031, and acrD were upregulated and that of ompW was downregulated in various cpxA mutants. Furthermore, the expression levels of nuoA and sdhC mRNAs were downregulated only in JSΔcpxA92–104. These results suggested that cpxA mutations contribute to AGAs and β-lactams resistance, which is dependent on CpxR.

scholarly journals Characterization of SlyA in Shigella flexneri Identifies a Novel Role in Virulence

2016 ◽  
Vol 84 (4) ◽  
pp. 1073-1082 ◽  
Author(s):  
Natasha Weatherspoon-Griffin ◽  
Helen J. Wing
Keyword(s):  
Response Regulator ◽  
Shigella Flexneri ◽  
Acid Resistance ◽  
Enteric Bacteria ◽  
Content Type ◽  
Related Organism ◽  
Serovar Typhimurium ◽  
Exogenous Expression

The SlyA transcriptional regulator has important roles in the virulence and pathogenesis of several members of theEnterobacteriaceaefamily, includingSalmonella entericaserovar Typhimurium andEscherichia coli. Despite the identification of theslyAgene inShigella flexnerinearly 2 decades ago, as well as the significant conservation of SlyA among enteric bacteria, the role of SlyA inShigellaremains unknown. The genes regulated by SlyA in closely related organisms often are absent from or mutated inS. flexneri, and consequently many described SlyA-dependent phenotypes are not present. By characterizing the expression ofslyAand determining its ultimate effect in this highly virulent organism, we postulated that novel SlyA-regulated virulence phenotypes would be identified. In this study, we report the first analysis of SlyA inShigellaand show that (i) theslyAgene is transcribed and ultimately translated into protein, (ii)slyApromoter activity is maximal during stationary phase and is negatively autoregulated and positively regulated by the PhoP response regulator, (iii) the exogenous expression ofslyArescues transcription and virulence-associated deficiencies during virulence-repressed conditions, and (iv) the absence ofslyAsignificantly decreases acid resistance, demonstrating a novel and important role inShigellavirulence. Cumulatively, our study illustrates unexpected parallels between the less conservedS. flexneriandS. TyphimuriumslyApromoters as well as a unique role for SlyA inShigellavirulence that has not been described previously in any closely related organism.

scholarly journals Regulation of igaA and the Rcs System by the MviA Response Regulator in Salmonella enterica

2009 ◽  
Vol 191 (8) ◽  
pp. 2743-2752 ◽  
Author(s):  
Clara B. García-Calderón ◽  
Josep Casadesús ◽  
Francisco Ramos-Morales
Keyword(s):  
Membrane Protein ◽  
Salmonella Enterica ◽  
Response Regulator ◽  
Regulatory System ◽  
Enteric Bacteria ◽  
Lon Protease ◽  
Dependent Manner ◽  
Independent Manner ◽  
Serovar Typhimurium

ABSTRACT IgaA is a membrane protein that prevents overactivation of the Rcs regulatory system in enteric bacteria. Here we provide evidence that igaA is the first gene in a σ70-dependent operon of Salmonella enterica serovar Typhimurium that also includes yrfG, yrfH, and yrfI. We also show that the Lon protease and the MviA response regulator participate in regulation of the igaA operon. Our results indicate that MviA regulates igaA transcription in an RpoS-dependent manner, but the results also suggest that MviA may regulate RcsB activation in an RpoS- and IgaA-independent manner.

scholarly journals YaeB, Expressed in Response to the Acidic pH in Macrophages, Promotes Intracellular Replication and Virulence of Salmonella Typhimurium

2019 ◽  
Vol 20 (18) ◽  
pp. 4339 ◽  
Author(s):  
Huan Zhang ◽  
Xiaorui Song ◽  
Peisheng Wang ◽  
Runxia Lv ◽  
Shuangshuang Ma ◽  
...  
Keyword(s):  
Salmonella Enterica Serovar Typhimurium ◽  
Intracellular Pathogen ◽  
Acidic Ph ◽  
Intracellular Replication ◽  
Global Regulator ◽  
Serovar Typhimurium ◽  
Survival And Growth ◽  
Bacterial Replication ◽  
Specific Transport System

Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that infects humans and animals. Survival and growth in host macrophages represents a crucial step for S. Typhimurium virulence. Many genes that are essential for S. Typhimurium proliferation in macrophages and associated with virulence are highly expressed during the intracellular lifecycle. yaeB, which encodes an RNA methyltransferase, is also upregulated during S. Typhimurium growth in macrophages. However, the involvement of YaeB in S. Typhimurium pathogenicity is still unclear. In this study, we investigated the role of YaeB in S. Typhimurium virulence. Deletion of yaeB significantly impaired S. Typhimurium growth in macrophages and virulence in mice. The effect of yaeB on pathogenicity was related to its activation of pstSCAB, a phosphate (Pi)-specific transport system that is verified here to be important for bacterial replication and virulence. Moreover, qRT-PCR data showed YaeB was induced by the acidic pH inside macrophages, and the acidic pH passed to YeaB through inhibiting global regulator histone-like nucleoid structuring (H-NS) which confirmed in this study can repress the expression of yaeB. Overall, these findings identified a new virulence regulatory network involving yaeB and provided valuable insights to the mechanisms through which acidic pH and low Pi regulate virulence.

scholarly journals Characterization of the Role of AMP-Activated Protein Kinase in the Regulation of Glucose-Activated Gene Expression Using Constitutively Active and Dominant Negative Forms of the Kinase

2000 ◽  
Vol 20 (18) ◽  
pp. 6704-6711 ◽  
Author(s):  
Angela Woods ◽  
Dalila Azzout-Marniche ◽  
Marc Foretz ◽  
Silvie C. Stein ◽  
Patricia Lemarchand ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Fatty Acid Synthase ◽  
Physiological Role ◽  
Rat Hepatocytes ◽  
Dominant Negative ◽  
Ampk Activity ◽  
Amp Activated Protein Kinase ◽  
Constitutively Active

ABSTRACT In the liver, glucose induces the expression of a number of genes involved in glucose and lipid metabolism, e.g., those encoding L-type pyruvate kinase and fatty acid synthase. Recent evidence has indicated a role for the AMP-activated protein kinase (AMPK) in the inhibition of glucose-activated gene expression in hepatocytes. It remains unclear, however, whether AMPK is involved in the glucose induction of these genes. In order to study further the role of AMPK in regulating gene expression, we have generated two mutant forms of AMPK. One of these (α1312) acts as a constitutively active kinase, while the other (α1DN) acts as a dominant negative inhibitor of endogenous AMPK. We have used adenovirus-mediated gene transfer to express these mutants in primary rat hepatocytes in culture in order to determine their effect on AMPK activity and the transcription of glucose-activated genes. Expression of α1312 increased AMPK activity in hepatocytes and blocked completely the induction of a number of glucose-activated genes in response to 25 mM glucose. This effect is similar to that observed following activation of AMPK by 5-amino-imidazolecarboxamide riboside. Expression of α1DN markedly inhibited both basal and stimulated activity of endogenous AMPK but had no effect on the transcription of glucose-activated genes. Our results suggest that AMPK is involved in the inhibition of glucose-activated gene expression but not in the induction pathway. This study demonstrates that the two mutants we have described will provide valuable tools for studying the wider physiological role of AMPK.

scholarly journals The Escherichia coli K-12 NarL and NarP Proteins Insulate the nrf Promoter from the Effects of Integration Host Factor

2006 ◽  
Vol 188 (21) ◽  
pp. 7449-7456 ◽  
Author(s):  
Douglas F. Browning ◽  
David J. Lee ◽  
Alan J. Wolfe ◽  
Jeffrey A. Cole ◽  
Stephen J. W. Busby
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Regulatory Region ◽  
Enteric Bacteria ◽  
Integration Host Factor ◽  
Host Factor ◽  
Receptor Protein ◽  
E Coli ◽  
Serovar Typhimurium ◽  
K 12

ABSTRACT The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position −41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position −54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position −74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acsP2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position −127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position −74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.

scholarly journals Role of Toll-Like Receptor 4 in Macrophage Activation and Tolerance during Salmonella enterica Serovar Typhimurium Infection

2003 ◽  
Vol 71 (9) ◽  
pp. 4873-4882 ◽  
Author(s):  
Qian Li ◽  
Bobby J. Cherayil
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Peritoneal Macrophages ◽  
Phagocytic Cells ◽  
Necrosis Factor Alpha ◽  
Tnf Α ◽  
Serovar Typhimurium ◽  
Tlr4 Gene ◽  
Factor Alpha

ABSTRACT Toll-like receptors (TLRs) play an important role in the innate immune response, particularly in the initial interaction between the infecting microorganism and phagocytic cells, such as macrophages. We investigated the role of TLR4 during infection of primary murine peritoneal macrophages with Salmonella enterica serovar Typhimurium. We found that macrophages from the C3H/HeJ mouse strain, which carries a functionally inactive Tlr4 gene, exhibit marked impairment of tumor necrosis factor alpha (TNF-α) secretion in response to S. enterica serovar Typhimurium infection. However, activation of extracellular growth factor-regulated kinase and NF-κB signaling pathways was relatively unaffected, as was increased expression of TNF-α mRNA. Furthermore, macrophage tolerance, which is associated with increased expression of the NF-κB p50 and p52 subunits, was induced by S. enterica serovar Typhimurium even in the absence of functional TLR4. These results indicate that during infection of macrophages by S. enterica serovar Typhimurium, TLR4 signals are required at a posttranscriptional step to maximize secretion of TNF-α. Signals delivered by pattern recognition receptors other than TLR4 are sufficient for the increased expression of the TNF-α transcript and at least some genes associated with macrophage tolerance.

scholarly journals Multiple Factors Independently RegulatehilA and Invasion Gene Expression in Salmonella enterica Serovar Typhimurium

2000 ◽  
Vol 182 (7) ◽  
pp. 1872-1882 ◽  
Author(s):  
Robin L. Lucas ◽  
C. Phoebe Lostroh ◽  
Concetta C. DiRusso ◽  
Michael P. Spector ◽  
Barry L. Wanner ◽  
...  
Keyword(s):  
Gene Expression ◽  
Salmonella Enterica ◽  
Inorganic Phosphate ◽  
Response Regulator ◽  
Regulatory System ◽  
Negative Control ◽  
Host Cells ◽  
Uptake System ◽  
Intracellular Signals ◽  
Serovar Typhimurium

HilA activates the expression of Salmonella entericaserovar Typhimurium invasion genes. To learn more about regulation ofhilA, we isolated Tn5 mutants exhibiting reduced hilA and/or invasion gene expression. In addition to expected mutations, we identified Tn5 insertions inpstS, fadD, flhD, flhC, and fliA. Analysis of the pstS mutant indicates that hilA and invasion genes are repressed by the response regulator PhoB in the absence of the Pst high-affinity inorganic phosphate uptake system. This system is required for negative control of the PhoR-PhoB two-component regulatory system, suggesting thathilA expression may be repressed by PhoR-PhoB under low extracellular inorganic phosphate conditions. FadD is required for uptake and degradation of long-chain fatty acids, and our analysis of the fadD mutant indicates that hilA is regulated by a FadD-dependent, FadR-independent mechanism. Thus, fatty acid derivatives may act as intracellular signals to regulatehilA expression. flhDC and fliAencode transcription factors required for flagellum production, motility, and chemotaxis. Complementation studies with flhCand fliA mutants indicate that FliZ, which is encoded in an operon with fliA, activates expression of hilA, linking regulation of hilA with motility. Finally, epistasis tests showed that PhoB, FadD, FliZ, SirA, and EnvZ act independently to regulate hilA expression and invasion. In summary, our screen has identified several distinct pathways that can modulate S. enterica serovar Typhimurium's ability to express hilA and invade host cells. Integration of signals from these different pathways may help restrict invasion gene expression during infection.

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