scholarly journals PhoP Can Activate Its Target Genes in a PhoQ-Independent Manner

2004 ◽  
Vol 186 (8) ◽  
pp. 2476-2480 ◽  
Author(s):  
Sergio Lejona ◽  
María Eugenia Castelli ◽  
María Laura Cabeza ◽  
Linda J. Kenney ◽  
Eleonora García Véscovi ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Target Genes ◽  
High Concentration ◽  
Two Component System ◽  
Independent Manner ◽  
Component System ◽  
Magnesium Depletion ◽  
Two Component ◽  
Self Association

ABSTRACT The PhoP/PhoQ two-component system controls the extracellular magnesium depletion response in Salmonella enterica. Previous studies have shown that PhoP is unable to up-regulate its target genes in the absence of PhoQ function. In this work, we demonstrate that PhoP overexpression can substitute for PhoQ- and phosphorylation-dependent activation. Either a high concentration of PhoP or activation via phosphorylation stimulates PhoP self-association.

scholarly journals Role of Salmonella enterica Serovar Typhimurium Two-Component System PreA/PreB in Modulating PmrA-Regulated Gene Transcription

2006 ◽  
Vol 188 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Massimo Merighi ◽  
Amanda Carroll-Portillo ◽  
Alecia N. Septer ◽  
Aditi Bhatiya ◽  
John S. Gunn
Keyword(s):  
Salmonella Enterica ◽  
Target Genes ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Response Regulator ◽  
Polymyxin B ◽  
Response Regulators ◽  
Two Component System ◽  
Component System ◽  
Two Component ◽  
Serovar Typhimurium

ABSTRACT The PmrA/PmrB two-component system encoded by the pmrCAB operon regulates the modification of Salmonella enterica serovar Typhimurium lipopolysaccharide leading to polymyxin B resistance. PmrA and PhoP are the only known activators of pmrCAB. A transposon mutagenesis screen for additional regulators of a pmrC::MudJ fusion led to the identification of a two-component system, termed PreA/PreB (pmrCAB regulators A and B), that controls the transcription of the pmrCAB operon in response to unknown signals. The initial observations indicated that insertions in, or a deletion of, the preB sensor, but not the preA response regulator, caused upregulation of pmrCAB. Interestingly, the expression of pmrCAB was not upregulated in a preAB mutant grown in LB broth, implicating PreA in the increased expression of pmrCAB in the preB strain. This was confirmed by overexpression of preA + in preAB or preB backgrounds, which resulted in significant upregulation or further upregulation of pmrCAB. No such effect was observed in any tested preB + backgrounds. Additionally, an ectopic construct expressing a preA[D51A] allele also failed to upregulate pmrC in any of the pre backgrounds tested, which implies that there is a need for phosphorylation in the activation of the target genes. The observed upregulation of pmrCAB occurred independently of the response regulators PmrA and PhoP. Although a preB mutation led to increased transcription of pmrCAB, this did not result in a measurable effect on polymyxin B resistance. Our genetic data support a model of regulation whereby, in response to unknown signals, the PreB sensor activates PreA, which in turn indirectly upregulates pmrCAB transcription.

scholarly journals Role of PhoP-PhoQ Two-Component System in Biofilm Formation of the Phytopathogen Dickeya dadantii Strain 3937

2010 ◽  
pp. 108-117
Author(s):  
Md Manjurul Haque ◽  
Shinji Tsuyumu
Keyword(s):  
Biofilm Formation ◽  
Transcriptional Control ◽  
Test Tube ◽  
Luria Bertani ◽  
High Concentration ◽  
Two Component System ◽  
Dickeya Dadantii ◽  
Component System ◽  
Two Component

To elucidate the role of PhoP-PhoQ two-component system in biofilm formation by the phytopathogen Dickeya dadantii (formerly Erwinia chrysanthemi) strain 3937, we used marker-exchanged mutants deficient in both phoP and phoQ. A biofilm-inducing medium, salt-optimized broth plus glycerol (SOBG) which contains salt-optimized broth (SOB) plus 2% of glycerol, supported biofilm formation by D. dadantii strain 3937 to a greater extent than either M63 glycerol minimal medium or yeast extract peptone (YP) medium or Luria-Bertani (LB) medium. In addition, magnesium greatly induced biofilm formation. It was found that both the phoP and phoQ mutants exhibited enhanced ability to form a biofilm on the surface of the glass test tube as compared to the wild-type strain in SOBG medium containing high concentration of magnesium. In addition, under high magnesium condition, both the mutants produced elevated level of exopolysaccharide. Accordingly, genes responsible for exopolysaccharide production (weaP, wza and wzc) were derepressed in the mutants. These results suggest that the PhoP-PhoQ two-component system may regulate formation of biofilm, at least in part, by transcriptional control of genes responsible for exopolysaccharide biosynthesis of D. dadantii strain 3937. Since biofilm-associated bacteria showed more tolerance to acidic pH and high osmotic stress, it is apparent that the formation of biofilm may be an important factor for the survival of D. dadantii strain 3937 in unfavorable environment.

scholarly journals Induction of RpoS Degradation by the Two-Component System Regulator RstA in Salmonella enterica

2007 ◽  
Vol 189 (20) ◽  
pp. 7335-7342 ◽  
Author(s):  
María L. Cabeza ◽  
Andrés Aguirre ◽  
Fernando C. Soncini ◽  
Eleonora García Véscovi
Keyword(s):  
Salmonella Enterica ◽  
Response Regulator ◽  
Control Point ◽  
Bacterial Survival ◽  
Two Component System ◽  
Component System ◽  
Regulatory Pathways ◽  
Regulatory Systems ◽  
Two Component ◽  
Serovar Typhimurium

ABSTRACT Bacterial survival in diverse and changing environments relies on the accurate interplay between different regulatory pathways, which determine the design of an adequate adaptive response. The proper outcome depends on a precise gene expression profile generated from the finely tuned and concerted action of transcriptional factors of distinct regulatory hierarchies. Salmonella enterica serovar Typhimurium harbors multiple regulatory systems that are crucial for the bacterium to cope with harsh extra- and intracellular environments. In this work, we found that the expression of Salmonella RstA, a response regulator from the two-component system family, was able to downregulate the expression of three RpoS-controlled genes (narZ, spvA, and bapA). Furthermore, this downregulation was achieved by a reduction in RpoS cellular levels. The alternative sigma factor RpoS is critical for bacterial endurance under the most-stressful conditions, including stationary-phase entrance and host adaptation. Accordingly, RpoS cellular levels are tightly controlled by complex transcriptional, translational, and posttranslational mechanisms. The analysis of each regulatory step revealed that in Salmonella, RstA expression was able to promote RpoS degradation independently of the MviA-ClpXP proteolytic pathway. Additionally, we show that RstA is involved in modulating Salmonella biofilm formation. The fact that the RpoS-modulated genes affected by RstA expression have previously been demonstrated to contribute to Salmonella pathogenic traits, which include biofilm-forming capacity, suggests that under yet unknown conditions, RstA may function as a control point of RpoS-dependent pathways that govern Salmonella virulence.

scholarly journals The ColRS Two-Component System Regulates Membrane Functions and Protects Pseudomonas putida against Phenol

2006 ◽  
Vol 188 (23) ◽  
pp. 8109-8117 ◽  
Author(s):  
Paula Ann Kivistik ◽  
Marta Putrinš ◽  
Külliki Püvi ◽  
Heili Ilves ◽  
Maia Kivisaar ◽  
...  
Keyword(s):  
Pseudomonas Putida ◽  
Target Genes ◽  
Type I ◽  
Two Component System ◽  
Component System ◽  
Two Component ◽  
Encoding Gene ◽  
Phenol Tolerance

ABSTRACT As reported, the two-component system ColRS is involved in two completely different processes. It facilitates the root colonization ability of Pseudomonas fluorescens and is necessary for the Tn4652 transposition-dependent accumulation of phenol-utilizing mutants in Pseudomonas putida. To determine the role of the ColRS system in P. putida, we searched for target genes of response regulator ColR by use of a promoter library. Promoter screening was performed on phenol plates to mimic the conditions under which the effect of ColR on transposition was detected. The library screen revealed the porin-encoding gene oprQ and the alginate biosynthesis gene algD occurring under negative control of ColR. Binding of ColR to the promoter regions of oprQ and algD in vitro confirmed its direct involvement in regulation of these genes. Additionally, the porin-encoding gene ompA PP0773 and the type I pilus gene csuB were also identified in the promoter screen. However, it turned out that ompA PP0773 and csuB were actually affected by phenol and that the influence of ColR on these promoters was indirect. Namely, our results show that ColR is involved in phenol tolerance of P. putida. Phenol MIC measurement demonstrated that a colR mutant strain did not tolerate elevated phenol concentrations. Our data suggest that increased phenol susceptibility is also the reason for inhibition of transposition of Tn4652 in phenol-starving colR mutant bacteria. Thus, the current study revealed the role of the ColRS two-component system in regulation of membrane functionality, particularly in phenol tolerance of P. putida.

scholarly journals Correlation between Ceftriaxone Resistance of Salmonella enterica Serovar Typhimurium and Expression of Outer Membrane Proteins OmpW and Ail/OmpX-Like Protein, Which Are Regulated by BaeR of a Two-Component System

2005 ◽  
Vol 49 (9) ◽  
pp. 3955-3958 ◽  
Author(s):  
Wensi S. Hu ◽  
Pei-Chuan Li ◽  
Chao-Yin Cheng
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Outer Membrane Proteins ◽  
Regulator Gene ◽  
Two Component System ◽  
Component System ◽  
Two Component ◽  
Serovar Typhimurium

ABSTRACT Mutant 7F2 of Salmonella enterica serovar Typhimurium has a transposon inserted in the regulator gene baeR of a two-component system and showed a more-than-fourfold reduction in resistance to ceftriaxone. Complementation analysis suggested an association among the outer membrane proteins OmpW and STM3031, ceftriaxone resistance, and baeR.

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