scholarly journals raiIR Genes Are Part of a Quorum-Sensing Network Controlled by cinI and cinR in Rhizobium leguminosarum

2002 ◽  
Vol 184 (6) ◽  
pp. 1597-1606 ◽  
Author(s):  
F. Wisniewski-Dyé ◽  
J. Jones ◽  
S. R. Chhabra ◽  
J. A. Downie
Keyword(s):  
Quorum Sensing ◽  
Rhizobium Leguminosarum ◽  
Homoserine Lactone ◽  
Major Product ◽  
Homoserine Lactones ◽  
Indigenous Plasmid ◽  
Sensing Systems ◽  
Regulatory Systems ◽  
Normal Expression ◽  
Low Levels

ABSTRACT Analysis of N-acyl-l-homoserine lactones (AHLs) produced by Rhizobium leguminosarum bv. viciae indicated that there may be a network of quorum-sensing regulatory systems producing multiple AHLs in this species. Using a strain lacking a symbiosis plasmid, which carries some of the quorum-sensing genes, we isolated mutations in two genes (raiI and raiR) that are required for production of AHLs. The raiIR genes are located adjacent to dad genes (involved in d-alanine catabolism) on a large indigenous plasmid. RaiR is predicted to be a typical LuxR-type quorum-sensing regulator and is required for raiI expression. The raiR gene was expressed at a low level, possibly from a constitutive promoter, and its expression was increased under the influence of the upstream raiI promoter. Using gene fusions and analysis of AHLs produced, we showed that expression of raiI is strongly reduced in strains carrying mutations in cinI or cinR, genes which determine a higher-level quorum-sensing system that is required for normal expression of raiIR. The product of CinI, N-(3-hydroxy-7-cis tetradecenoyl) homoserine lactone, can induce raiR-dependent raiI expression, although higher levels of expression are induced by other AHLs. Expression of raiI in a strain of Agrobacterium that makes no AHLs resulted in the identification of N-(3-hydroxyoctanoyl)-l-homoserine lactone (3OH,C8-HSL) as the major product of RaiI, although other AHLs that comigrate with N-hexanoyl-, N-heptanoyl-, and N-octanoyl-homoserine lactones were also made at low levels. The raiI gene was strongly induced by 3OH,C8-HSL (the product of RaiI) but could also be induced by other AHLs, suggesting that the raiI promoter can be activated by other quorum-sensing systems within a network of regulation which also involves AHLs determined by genes on the symbiotic plasmid. Thus, the raiIR and cinIR genes are part of a complex regulatory network that influences AHL biosynthesis in R. leguminosarum.

scholarly journals Quorum-sensing regulation in rhizobia and its role in symbiotic interactions with legumes

2007 ◽  
Vol 362 (1483) ◽  
pp. 1149-1163 ◽  
Author(s):  
Maria Sanchez-Contreras ◽  
Wolfgang D Bauer ◽  
Mengsheng Gao ◽  
Jayne B Robinson ◽  
J Allan Downie
Keyword(s):  
Quorum Sensing ◽  
Potential Role ◽  
Active Role ◽  
Dependent Manner ◽  
Homoserine Lactones ◽  
Signalling Molecules ◽  
Sensing Systems ◽  
Symbiotic Interactions ◽  
Regulatory Systems

Legume-nodulating bacteria (rhizobia) usually produce N -acyl homoserine lactones, which regulate the induction of gene expression in a quorum-sensing (or population-density)-dependent manner. There is significant diversity in the types of quorum-sensing regulatory systems that are present in different rhizobia and no two independent isolates worked on in detail have the same complement of quorum-sensing genes. The genes regulated by quorum sensing appear to be rather diverse and many are associated with adaptive aspects of physiology that are probably important in the rhizosphere. It is evident that some aspects of rhizobial physiology related to the interaction between rhizobia and legumes are influenced by quorum sensing. However, it also appears that the legumes play an active role, both in terms of interfering with the rhizobial quorum-sensing systems and responding to the signalling molecules made by the bacteria. In this article, we review the diversity of quorum-sensing regulation in rhizobia and the potential role of legumes in influencing and responding to this signalling system.

scholarly journals Control of Quorum Sensing by a Burkholderia pseudomallei Multidrug Efflux Pump

2007 ◽  
Vol 189 (11) ◽  
pp. 4320-4324 ◽  
Author(s):  
Ying Ying Chan ◽  
Hao Sheng Bian ◽  
Theresa May Chin Tan ◽  
Margrith E. Mattmann ◽  
Grant D. Geske ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Burkholderia Pseudomallei ◽  
Efflux Pump ◽  
Homoserine Lactone ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Homoserine Lactones ◽  
Extracellular Secretion ◽  
Sensing Systems ◽  
Acyl Homoserine Lactones

ABSTRACT The Burkholderia pseudomallei KHW quorum-sensing systems produced N-octanoyl-homoserine lactone, N-decanoyl-homoserine lactone, N-(3-hydroxy)-octanoyl-homoserine lactone, N-(3-hydroxy)-decanoyl-homoserine lactone, N-(3-oxo)-decanoyl-homoserine lactone, and N-(3-oxo)-tetradecanoyl-homoserine lactone. The extracellular secretion of these acyl-homoserine lactones is dependent absolutely on the function of the B. pseudomallei BpeAB-OprB efflux pump.

scholarly journals Quorum Sensing in Rhizobium sp. Strain NGR234 Regulates Conjugal Transfer (tra) Gene Expression and Influences Growth Rate

2003 ◽  
Vol 185 (3) ◽  
pp. 809-822 ◽  
Author(s):  
Xuesong He ◽  
William Chang ◽  
Deanne L. Pierce ◽  
Laura Ort Seib ◽  
Jennifer Wagner ◽  
...  
Keyword(s):  
Growth Rate ◽  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Ti Plasmid ◽  
Conjugal Transfer ◽  
Signal Molecule ◽  
Sensing Systems ◽  
Ti Plasmids ◽  
Wide Range ◽  
Low Levels

ABSTRACT Rhizobium sp. strain NGR234 forms symbiotic, nitrogen-fixing nodules on a wide range of legumes via functions largely encoded by the plasmid pNGR234a. The pNGR234a sequence revealed a region encoding plasmid replication (rep) and conjugal transfer (tra) functions similar to those encoded by the rep and tra genes from the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens, including homologues of the Ti plasmid quorum-sensing regulators TraI, TraR, and TraM. In A. tumefaciens, TraI, a LuxI-type protein, catalyzes synthesis of the acylated homoserine lactone (acyl-HSL) N-3-oxo-octanoyl-l-homoserine lactone (3-oxo-C8-HSL). TraR binds 3-oxo-C8-HSL and activates expression of Ti plasmid tra and rep genes, increasing conjugation and copy number at high population densities. TraM prevents this activation under noninducing conditions. Although the pNGR234a TraR, TraI, and TraM appear to function similarly to their A. tumefaciens counterparts, the TraR and TraM orthologues are not cross-functional, and the quorum-sensing systems have differences. NGR234 TraI synthesizes an acyl-HSL likely to be 3-oxo-C8-HSL, but traI mutants and a pNGR234a-cured derivative produce low levels of a similar acyl-HSL and another, more hydrophobic signal molecule. TraR activates expression of several pNGR234a tra operons in response to 3-oxo-C8-HSL and is inhibited by TraM. However, one of the pNGR234a tra operons is not activated by TraR, and conjugal efficiency is not affected by TraR and 3-oxo-C8-HSL. The growth rate of NGR234 is significantly decreased by TraR and 3-oxo-C8-HSL through functions encoded elsewhere in the NGR234 genome.

scholarly journals The cin and rai Quorum-Sensing Regulatory Systems in Rhizobium leguminosarum Are Coordinated by ExpR and CinS, a Small Regulatory Protein Coexpressed with CinI

2009 ◽  
Vol 191 (9) ◽  
pp. 3059-3067 ◽  
Author(s):  
Anne Edwards ◽  
Marijke Frederix ◽  
Florence Wisniewski-Dyé ◽  
Jacob Jones ◽  
Angeles Zorreguieta ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Rhizobium Leguminosarum ◽  
Regulatory Protein ◽  
Colony Structure ◽  
Homoserine Lactones ◽  
Bacterial Surface ◽  
Sensing System ◽  
Regulatory Systems ◽  
Quorum Sensing System ◽  
Regulatory Effects

ABSTRACT To understand how the Rhizobium leguminosarum raiI-raiR quorum-sensing system is regulated, we identified mutants with decreased levels of RaiI-made N-acyl homoserine lactones (AHLs). A LuxR-type regulator, ExpR, is required for raiR expression, and RaiR is required to induce raiI. Since raiR (and raiI) expression is also reduced in cinI and cinR quorum-sensing mutants, we thought CinI-made AHLs may activate ExpR to induce raiR. However, added CinI-made AHLs did not induce raiR expression in a cinI mutant. The reduced raiR expression in cinI and cinR mutants was due to lack of expression of cinS immediately downstream of cinI. cinS encodes a 67-residue protein, translationally coupled to CinI, and cinS acts downstream of expR for raiR induction. Cloned cinS in R. leguminosarum caused an unusual collapse of colony structure, and this was delayed by mutation of expR. The phenotype looked like a loss of exopolysaccharide (EPS) integrity; mutations in cinI, cinR, cinS, and expR all reduced expression of plyB, encoding an EPS glycanase, and mutation of plyB abolished the effect of cloned cinS on colony morphology. We conclude that CinS and ExpR act to increase PlyB levels, thereby influencing the bacterial surface. CinS is conserved in other rhizobia, including Rhizobium etli; the previously observed effect of cinI and cinR mutations decreasing swarming in that strain is primarily due to a lack of CinS rather than a lack of CinI-made AHL. We conclude that CinS mediates quorum-sensing regulation because it is coregulated with an AHL synthase and demonstrate that its regulatory effects can occur in the absence of AHLs.

scholarly journals Revisiting the quorum-sensing hierarchy in Pseudomonas aeruginosa: the transcriptional regulator RhlR regulates LasR-specific factors

Microbiology ◽  
2009 ◽  
Vol 155 (3) ◽  
pp. 712-723 ◽  
Author(s):  
Valérie Dekimpe ◽  
Eric Déziel
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Transcriptional Regulator ◽  
Homoserine Lactone ◽  
The Other ◽  
Virulence Determinants ◽  
Late Stationary Phase ◽  
Regulatory Systems ◽  
Specific Factors

Pseudomonas aeruginosa uses the two major quorum-sensing (QS) regulatory systems las and rhl to modulate the expression of many of its virulence factors. The las system is considered to stand at the top of the QS hierarchy. However, some virulence factors such as pyocyanin have been reported to still be produced in lasR mutants under certain conditions. Interestingly, such mutants arise spontaneously under various conditions, including in the airways of cystic fibrosis patients. Using transcriptional lacZ reporters, LC/MS quantification and phenotypic assays, we have investigated the regulation of QS-controlled factors by the las system. Our results show that activity of the rhl system is only delayed in a lasR mutant, thus allowing the expression of multiple virulence determinants such as pyocyanin, rhamnolipids and C4-homoserine lactone (HSL) during the late stationary phase. Moreover, at this stage, RhlR is able to overcome the absence of the las system by activating specific LasR-controlled functions, including production of 3-oxo-C12-HSL and Pseudomonas quinolone signal (PQS). P. aeruginosa is thus able to circumvent the deficiency of one of its QS systems by allowing the other to take over. This work demonstrates that the QS hierarchy is more complex than the model simply presenting the las system above the rhl system.

Functional analysis of three AHL autoinducer synthase genes in Mesorhizobium loti reveals the important role of quorum sensing in symbiotic nodulation

2009 ◽  
Vol 55 (2) ◽  
pp. 210-214 ◽  
Author(s):  
Menghua Yang ◽  
Kejing Sun ◽  
Lei Zhou ◽  
Ruifu Yang ◽  
Zengtao Zhong ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Culture Conditions ◽  
Native Plant ◽  
Plant Host ◽  
Mesorhizobium Loti ◽  
Sensing Systems ◽  
Regulatory Circuits ◽  
Legume Symbiosis ◽  
Successful Establishment

One of the most important signal transduction pathways in bacteria, quorum sensing, is involved in many regulatory circuits in rhizobia, especially in the control of communication between rhizobia and their plant hosts. In this study, we identified 3 autoinducer synthase genes — mrlI1, mrlI2, and mrlI3 — in Mesorhizobium loti NZP 2213. We found that MrlI1 and MrlI2 could synthesize distinct N-acyl homoserine lactone (AHL) autoinducers in rich medium cultures, and the expression of mrlI1 was shown to be growth-phase-dependent. MrlI3 did not produce any detectable AHL molecules under the culture conditions tested. To investigate whether these AHL synthases affect nodulation, we examined the nodulation of AHL-deficient mutants on their native plant host Lotus corniculatus and found that the efficiency of nodulation of bacteria with mutations of any of these 3 synthase genes was reduced, suggesting that quorum sensing systems in M. loti may play an important role in successful establishment of rhizobium–legume symbiosis.

scholarly journals Stringent Response Activates Quorum Sensing and Modulates Cell Density-Dependent Gene Expression inPseudomonas aeruginosa

2001 ◽  
Vol 183 (18) ◽  
pp. 5376-5384 ◽  
Author(s):  
Christian van Delden ◽  
Rachel Comte ◽  
And Marc Bally
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Cell Density ◽  
Stringent Response ◽  
Transcriptional Regulators ◽  
Homoserine Lactone ◽  
Density Dependent ◽  
Sensing Systems ◽  
Acid Analogue ◽  
Enhanced Expression

ABSTRACT During nutrient starvation, Escherichia coli elicits a stringent response involving the ribosome-associated protein RelA. Activation of RelA results in a global change in the cellular metabolism including enhanced expression of the stationary-phase sigma factor RpoS. In the human pathogen Pseudomonas aeruginosa, a complex quorum-sensing circuitry, linked to RpoS expression, is required for cell density-dependent production of many secreted virulence factors, including LasB elastase. Quorum sensing relies on the activation of specific transcriptional regulators (LasR and RhlR) by their corresponding autoinducers (3-oxo-C12-homoserine lactone [HSL] and C4-HSL), which function as intercellular signals. We found that overexpression of relA activated the expression of rpoS in P. aeruginosa and led to premature, cell density-independent LasB elastase production. We therefore investigated the effects of the stringent response on quorum sensing. Both lasR and rhlR gene expression and autoinducer synthesis were prematurely activated during the stringent response induced by overexpression of relA. Premature expression of lasR and rhlR was also observed when relA was overexpressed in a PAO1 rpoSmutant. The stringent response induced by the amino acid analogue serine hydroxamate (SHX) also led to premature production of the 3-oxo-C12-HSL autoinducer. This response to SHX was absent in a PAO1 relA mutant. These findings suggest that the stringent response can activate the two quorum-sensing systems of P. aeruginosa independently of cell density.

scholarly journals Distribution of Quorum-Sensing Genes in the Burkholderia cepacia Complex

2001 ◽  
Vol 69 (7) ◽  
pp. 4661-4666 ◽  
Author(s):  
E. Lutter ◽  
S. Lewenza ◽  
J. J. Dennis ◽  
M. B. Visser ◽  
P. A. Sokol
Keyword(s):  
Quorum Sensing ◽  
Burkholderia Cepacia ◽  
Homoserine Lactone ◽  
Burkholderia Cepacia Complex ◽  
Homoserine Lactones

ABSTRACT The distribution of quorum-sensing genes among strains from seven genomovars of the Burkholderia cepaciacomplex was examined by PCR. cepR and cepI were amplified from B. cepacia genomovars I and III, B. stabilis, and B. vietnamiensis. cepR was also amplified from B. multivorans and B. cepacia genomovar VI. bviIR were amplified from B. vietnamiensis. All genomovars producedN-octanoyl-l-homoserine lactone andN-hexanoyl-l-homoserine lactone.B. vietnamiensis and B. cepacia genomovar VII produced additional N-acyl-l-homoserine lactones.

scholarly journals Degradation of N-Acyl-l-Homoserine Lactones by Bacillus cereus in Culture Media and Pork Extract

2007 ◽  
Vol 73 (7) ◽  
pp. 2329-2332 ◽  
Author(s):  
Maria Stella Medina-Martínez ◽  
Mieke Uyttendaele ◽  
Andreja Rajkovic ◽  
Pol Nadal ◽  
Johan Debevere
Keyword(s):  
Quorum Sensing ◽  
Bacillus Cereus ◽  
Yersinia Enterocolitica ◽  
Culture Medium ◽  
Culture Media ◽  
Homoserine Lactone ◽  
Microbial Interaction ◽  
Signal Molecule ◽  
Homoserine Lactones ◽  
Degrading Bacterium

ABSTRACT Degradation of the quorum-sensing signal molecule N-acyl-l-homoserine lactone (AHL) in cocultures was verified with Bacillus cereus and Yersinia enterocolitica in culture medium and in pork extract. Results showed evidence of microbial interaction when the AHL-degrading bacterium and AHL-producing bacterium were cocultured in a food-simulating condition.

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