A novel two-component system BqsS-BqsR modulates quorum sensing-dependent biofilm decay inPseudomonas aeruginosa

Concerted investigations of factors affecting host-pathogen interactions are now possible with the model plant Arabidopsis thaliana and its model pathogen Pseudomo-nas syringae pv. tomato DC3000, as their whole genome sequences have become available. As a prelude to analysis of the regulatory genes and their targets, we have focused on GacA, the response regulator of a two-component system. The DC3000 gene was cloned by testing for the reversal of phenotypes of an Erwinia GacA− mutant. A GacA− mutant of DC3000 constructed by marker exchange produces much-reduced levels of transcripts of three alternate sigma factors: HrpL, required for the production of effector proteins and their translocation via the type III secretion system; RpoS, required for stress responses and secondary metabolite production; and RpoN, required for an assortment of metabolic processes and expression of hrpL. GacA deficiency also reduces the expression of hrpR and hrpS, which specify enhancer-binding proteins of the NtrC family required for hrpL transcription; ahlI and ahlR, the genes for quorum sensing signal; salA, a regulatory gene known to control virulence; CorS, a sensor kinase; CorR, the cognate response regulator that controls coronatine biosynthetic genes; and rsmB and rsmZ, which specify untranslatable regulatory RNA species. gacA expression itself is regulated by environmental conditions in DC3000, since transcript levels are affected by growth phase and media composition. The observations that high levels of gacA RNA occur in the hrp-inducing medium and GacA deficiency reduces the levels of rpoS expression implicate an important role of GacA in stress responses of DC3000. Consistent with the effects on hrpL expression, the GacA− mutant produces lower levels of transcripts of avr, hrp, and hop genes controlled by HrpL. In addition, GacA deficiency results in reduced levels of transcripts of several HrpL-independent genes. As would be expected, these effects on gene expression cause drastic changes in bacterial behavior: virulence towards A. thaliana and tomato; multiplication in planta; efficiency of the induction of the hypersensitive reaction (HR); production of pigment and N-acyl-homoserine lactone (AHL), the presumed quorum-sensing signal; and swarming motility. Our findings establish that GacA, located at the top in a regulatory cascade in DC3000, functions as a central regulator by controlling an assortment of transcriptional and posttranscriptional factors.

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Diffusible Signal Factor-Mediated Quorum Sensing Plays a Central Role in Coordinating Gene Expression of Xanthomonas citri subsp. citri

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-07-11-0184 ◽

2012 ◽

Vol 25 (2) ◽

pp. 165-179 ◽

Cited By ~ 43

Author(s):

Yinping Guo ◽

Yanping Zhang ◽

Jian-Liang Li ◽

Nian Wang

Keyword(s):

Quorum Sensing ◽

Wild Type Strain ◽

Xanthomonas Citri ◽

Two Component System ◽

Signal Molecule ◽

Component System ◽

Signal Perception ◽

Two Component ◽

Diffusible Signal Factor ◽

Unique Genes

Diffusible signal factor (DSF) family signal-mediated quorum sensing (QS) has been identified in many gram-negative bacteria. This QS pathway of Xanthomonas spp. consists of three major QS components: RpfF, RpfC, and RpfG. The rpfF gene encodes a putative enoyl-CoA hydratase that catalyzes the synthesis of the signal molecule. RpfC and RpfG serve as a two-component system for the perception and transduction of the extracellular DSF family signals. In order to further characterize the QS regulatory network in Xanthomonas citri subsp. citri, we investigated the RpfF, RpfC, and RpfG regulons by using transcriptome analyses. Comparison of the transcriptomes of the QS mutants (rpfF, rpfC, and rpfG) with that of the wild-type strain revealed a core group of genes controlled by all three QS components, suggesting that the RpfC-RpfG two-component system is a major and conserved signal perception and transduction system for DSF family signal-mediated QS in X. citri subsp. citri. The unique genes controlled by RpfF alone indicate the complexity of the QS pathway and the involvement of additional sensory mechanisms in X. citri subsp. citri. The unique genes controlled by RpfC and RpfG, respectively, support the possibility that RpfC and RpfG play broader roles in gene regulation other than transduction of DSF signals.

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A novel PilR/PilS two-component system regulates NE pilus production in Clostridium perfringens

Journal of Bacteriology ◽

10.1128/jb.00096-21 ◽

2021 ◽

Author(s):

Yuanyuan Zhou ◽

Dion Lepp ◽

Jason Carere ◽

Hai Yu ◽

Chengbo Yang ◽

...

Keyword(s):

Quorum Sensing ◽

Clostridium Perfringens ◽

Binding Activity ◽

Necrotic Enteritis ◽

Wild Type ◽

Two Component System ◽

Collagen Binding ◽

Component System ◽

Two Component

Clostridium perfringens causes necrotic enteritis (NE) in poultry. A chromosomal locus (VR-10B) was previously identified in NE-causing C. perfringens strains that encodes an adhesive pilus (NE pilus), along with a two-component system (TCS), designated here as PilRS. While the NE pilus is important in pathogenesis, the role of PilRS remains to be determined. The current study investigated the function of PilRS, as well as the Agr-like quorum-sensing (QS) system and VirSR TCS, in the regulation of pilin production. Isogenic pilR , agrB and virR null mutants were generated from parent strain CP1 by insertional inactivation using the ClosTron system, along with the respective complemented strains. Immunoblotting analyses showed no detectable pilus production in the CP1 pilR mutant, while production in its complement (CP1 pilR +) was greater than wild-type levels. In contrast, pilus production in the agrB and virR mutants was comparable or higher than the wild type, but reduced in their respective complemented strains. When examined for collagen-binding activity, the pilR mutant showed significantly lower binding to most collagen types (types I – V) than CP1 ( p ≤ 0.05), whereas this activity was restored in the complemented strain ( p > 0.05). In contrast, binding of agrB and virR mutants to collagen showed no significant differences in collagen-binding activity compared to CP1 ( p > 0.05), whereas the complemented strains exhibited significantly reduced binding ( p ≤ 0.05). These data suggest that the PilRS TCS positively regulates pilus production in C. perfringens , while the Agr-like QS system may serve as a negative regulator of this operon. Importance Clostridium perfringens type G isolates cause necrotic enteritis (NE) in poultry, presenting a major challenge for poultry production in the post-antibiotic era. Multiple factors in C. perfringens , including both virulent and non-virulent, are involved in the development of the disease. We previously discovered a cluster of C. perfringens genes that encode a pilus involved in adherence and NE development and a predicted two-component regulatory system (TCS), designated PilRS. In the present study, we have demonstrated the role of PilRS in regulating pilus production and collagen binding of C. perfringens . In addition, the Agr-like quorum sensing signalling pathway was found to be involved in the regulation. These findings have identified additional targets for developing non-antibiotic strategies to control NE disease.

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The VarS/VarA two-component system modulates the activity of the Vibrio cholerae quorum-sensing transcriptional regulator HapR

Microbiology ◽

10.1099/mic.0.046235-0 ◽

2011 ◽

Vol 157 (6) ◽

pp. 1620-1628 ◽

Cited By ~ 33

Author(s):

Amy M. Tsou ◽

Zhi Liu ◽

Tao Cai ◽

Jun Zhu

Keyword(s):

Quorum Sensing ◽

Vibrio Cholerae ◽

Cell Density ◽

Transcriptional Regulator ◽

Nutrient Status ◽

Two Component System ◽

Protein Activity ◽

Component System ◽

Its Gene ◽

Two Component

The human pathogen Vibrio cholerae uses quorum sensing to regulate the expression of a number of phenotypes, including virulence factor production, in response to changes in cell density. It produces small molecules called autoinducers that increase in concentration as cell density increases, and these autoinducers bind to membrane sensors once they reach a certain threshold. This binding leads to signalling through a downstream phosphorelay pathway to alter the expression of the transcriptional regulator HapR. Previously, it was shown that the VarS/VarA two-component system acts on a component of the phosphorelay pathway upstream of HapR to regulate HapR expression levels. Here, we show that in addition to this mechanism of regulation, VarS and VarA also indirectly modulate HapR protein activity. This modulation is mediated by the small RNA CsrB but is independent of the known quorum-sensing system that links the autoinducers to HapR. Thus, the VarS/VarA two-component system intersects with the quorum-sensing network at two levels. In both cases, the effect of VarS and VarA on quorum sensing is dependent on the Csr small RNAs, which regulate carbon metabolism, suggesting that V. cholerae may integrate nutrient status and cell density sensory inputs to tailor its gene expression profile more precisely to surrounding conditions.

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Integration of Transcriptome and Metabolome Reveals the Genes and Metabolites Involved in Bifidobacterium bifidum Biofilm Formation

International Journal of Molecular Sciences ◽

10.3390/ijms22147596 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7596

Author(s):

Zongmin Liu ◽

Lingzhi Li ◽

Zhifeng Fang ◽

Yuankun Lee ◽

Jianxin Zhao ◽

...

Keyword(s):

Quorum Sensing ◽

Biofilm Formation ◽

Bifidobacterium Bifidum ◽

Differentially Expressed ◽

Glutathione Metabolism ◽

Two Component System ◽

Metabolomics Data ◽

Component System ◽

Abiotic Surfaces ◽

Two Component

Bifidobacterium bifidum strains, an important component of probiotic foods, can form biofilms on abiotic surfaces, leading to increased self-resistance. However, little is known about the molecular mechanism of B. bifidum biofilm formation. A time series transcriptome sequencing and untargeted metabolomics analysis of both B. bifidum biofilm and planktonic cells was performed to identify key genes and metabolites involved in biofilm formation. Two hundred thirty-five nonredundant differentially expressed genes (DEGs) (including vanY, pstS, degP, groS, infC, groL, yajC, tadB and sigA) and 219 nonredundant differentially expressed metabolites (including L-threonine, L-cystine, L-tyrosine, ascorbic acid, niacinamide, butyric acid and sphinganine) were identified. Thirteen pathways were identified during the integration of both transcriptomics and metabolomics data, including ABC transporters; quorum sensing; two-component system; oxidative phosphorylation; cysteine and methionine metabolism; glutathione metabolism; glycine, serine and threonine metabolism; and valine, leucine and isoleucine biosynthesis. The DEGs that relate to the integration pathways included asd, atpB, degP, folC, ilvE, metC, pheA, pstS, pyrE, serB, ulaE, yajC and zwf. The differentially accumulated metabolites included L-cystine, L-serine, L-threonine, L-tyrosine, methylmalonate, monodehydroascorbate, nicotinamide, orthophosphate, spermine and tocopherol. These results indicate that quorum sensing, two-component system and amino acid metabolism are essential during B. bifidum biofilm formation.

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