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 The BpsIR Quorum-Sensing System of Burkholderia pseudomallei

2005 ◽  
Vol 187 (2) ◽  
pp. 785-790 ◽  
Author(s):  
Yan Song ◽  
Chao Xie ◽  
Yong-Mei Ong ◽  
Yunn-Hwen Gan ◽  
Kim-Lee Chua
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Burkholderia Pseudomallei ◽  
Homoserine Lactone ◽  
Positive Regulation ◽  
Density Dependent ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT BpsIR, a LuxIR quorum-sensing homolog, is required for optimal expression of virulence and secretion of exoproducts in Burkholderia pseudomallei. Cell density-dependent expression of bpsI and bpsR, the positive regulation of bpsIR expression by BpsR, and the synthesis of N-octanoyl-homoserine lactone (C8HSL) by BpsI are described in this report.

scholarly journals Perspectives on Quorum sensing in Fungi

2015 ◽  
Author(s):  
Sarangam Majumdar ◽  
Subhoshmita Mondal
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Density Dependent ◽  
Sensing Systems ◽  
Fungal Kingdom ◽  
Density Dependent Regulation

Keeping a pace with Quorum sensing, analyzing communication shows the close co-evolution of fungi with organisms present in their environment giving insights into multispecies communication. Subsequently, many examples of cell density dependent regulation by extracellular factors have been found in diverse microorganisms. The widespread incidence of diverse quorum-sensing systems strongly suggests that regulation in accordance with cell density is important for the success of microbes in many environments. The paper includes the basic autoregulatory quorum sensing molecules that has been perceived. Although fungal quorum sensing research is still in its infancy, its discovery has changed our views about the fungal kingdom and could eventually lead to the development of new antifungal therapeutics.

scholarly journals A single intracellular protein governs the critical transition from an individual to a coordinated population response during quorum sensing: Origins of primordial language

2016 ◽  
Author(s):  
Celina Vila-Sanjurjo ◽  
Christoph Engwer ◽  
Xiaofei Qin ◽  
Lea Hembach ◽  
Tania Verdía-Cotelo ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Density Dependence ◽  
Cell Density ◽  
Fluorescence Intensity ◽  
Percolation Theory ◽  
Bacterial Cell ◽  
Cell Communication ◽  
Critical Time ◽  
Homoserine Lactone ◽  
Density Dependent

Quorum sensing (QS) explains a type of bacterial cell-cell communication mediated by exocellular compounds that act as autoinducers (AIs). As such, QS can be considered the most primordial form of language. QS has profound implications for the control of many important traits (e.g.biofilm formation, secretion of virulence factors, etc.). Conceptually, the QS response can be split into its “listening” and “speaking” components,i.e.the power to sense AI levelsvs.the ability to synthesize and release these molecules. By explaining the cell-density dependence of QS behavior as the consequence of the system’s arrival to a threshold AI concentration, models of QS have traditionally assumed a salient role for the “QS speaking” module during bacterial cell-to-cell communication. In this paper, we have provided evidence that challenges this AI-centered view of QS and establishes LuxR-like activators at the center of QS. Our observation that highly coordinated, cell-density dependent responses can occur in the absence of AI production, implies that the ability to launch such responses is engrained within the “QS listening” module. Our data indicates that once a critical threshold of intracellular activator monomers in complex with AI is reached, a highly orchestrated QS response ensues. While displaying a clear cell-density dependence, such response does not strictly require the sensing of population levels by individual cells. We additionally show, bothin vivoandin silico, that despite their synchronous nature, QS responses do not require that all the cells in the population participate in the response. Central to our analysis was the discovery that percolation theory (PT) can be used to mathematically describe QS responses. While groundbreaking, our results are in agreement with and integrate the latest conclusions reached in the field. We explain for the first time, the cell-density-dependent synchronicity of QS responses as the function of a single protein, the LuxR-like activator, capable of coordinating the temporal response of a population of cells in the absence of cell-to-cell communication. Being QS the most primordial form of speech, our results have important implications for the evolution of language in its ancient chemical form.Abbreviations3Dthree dimensionalacwthreshold intracellular concentration of activator moleculesAHLacyl-homoserine lactoneAHLfischN-(3-oxohexanoyl)-L-homoserine lactoneAHLviolN-hexanoyl-DL-homoserine-lactoneAIautoinducera.uarbitrary unitsBMBbromophenol blueCAtrans-cinnamaldehydeFlfluorescence intensityFI/OD600density-normalized fluorescence intensityGFPgreen fluorescent proteinMwmolecular weightPTpercolation theoryQSquorum sensingtcpercolation critical timewtwild type

scholarly journals The AinS autoinducer synthase and LitR master regulator of quorum sensing regulate N-3-hydroxy-decanoyl-homoserine-lactone production and motility in Aliivibrio wodanis 06/09/139

2019 ◽  
Author(s):  
Amudha Deepalakshmi Maharajan ◽  
Hilde Hansen ◽  
Nils Peder Willassen
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Homoserine Lactone ◽  
Temperature Tolerance ◽  
Dependent Manner ◽  
Secretion Systems ◽  
Master Regulator ◽  
Density Dependent ◽  
Ulcer Disease ◽  
A Cell

Abstract Background Quorum Sensing (QS) is a cell to cell communication system, in which bacteria synthesize and respond to signaling molecules called autoinducers (AI). QS is cell density dependent and known to be involved in regulating virulence, motility and secretion systems to interact with the host or other bacteria. Aliivibrio wodanis is frequently isolated together with Moritella viscosa from the infected Atlantic salmon during outbreaks of the winter ulcer disease. M. viscosa is the main causative agent of the disease while the presence of A. wodanis is still unclear. It is hypothesized that A. wodanis might influence the progression of winter ulcer. The genome of A. wodanis 06/09/139 encodes two autoinducer synthase genes (ainS and luxS) and a master regulator litR. LitR homologs in other aliivibrios have been shown to regulate several phenotypes in a cell density dependent manner. Moreover, a previous study has shown that A. wodanis 06/09/139 produces only one AHL N-3-hydroxy-decanoyl-homoserine-lactone (3OHC10-HSL). Hence, in this work, we have studied the QS system in A. wodanis 06/09/139 by knocking out QS genes ainS and litR. The effects of the deletions were studied with regard to growth, AHL production and motility at different temperatures. Results By using HPLC-MS/MS, we found that the deletion of ainS in A. wodanis 06/09/139 resulted in the loss of 3OHC10-HSL production. The 3OHC10-HSL production in A. wodanis 06/09/139 increased with increase in cell density and more 3OHC10-HSL was produced at 6°C than at 12, 16 and 20°C. The litR mutant demonstrated a ~20% reduction in the production of 3OHC10-HSL relative to the wild type at the stationary phase. Compared to the wildtype and the ainS mutant strains, the litR mutant resulted in a strain with improved temperature tolerance. The motility in mutants (∆litR and ∆ainS) were significantly higher than that of the wildtype. Conclusions Our study shows that AinS in A. wodanis 06/09/139 is the AHL synthase responsible for 3OHC10-HSL production, where the production is both cell density and temperature dependent. Our data also shows that LitR regulates 3OHC10-HSL production only to a minor extent and both LitR and AinS are negative regulators of motility.

scholarly journals Peptide signaling without feedback in signal production operates as a true quorum sensing communication system in Bacillus subtilis

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Iztok Dogsa ◽  
Mihael Spacapan ◽  
Anna Dragoš ◽  
Tjaša Danevčič ◽  
Žiga Pandur ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bacillus Subtilis ◽  
Quorum Sensing ◽  
Cell Density ◽  
Communication System ◽  
Communication Systems ◽  
Feedback Loop ◽  
Signal Molecules ◽  
Specific Cell ◽  
Sharp Transition

AbstractBacterial quorum sensing (QS) is based on signal molecules (SM), which increase in concentration with cell density. At critical SM concentration, a variety of adaptive genes sharply change their expression from basic level to maximum level. In general, this sharp transition, a hallmark of true QS, requires an SM dependent positive feedback loop, where SM enhances its own production. Some communication systems, like the peptide SM-based ComQXPA communication system of Bacillus subtilis, do not have this feedback loop and we do not understand how and if the sharp transition in gene expression is achieved. Based on experiments and mathematical modeling, we observed that the SM peptide ComX encodes the information about cell density, specific cell growth rate, and even oxygen concentration, which ensure power-law increase in SM production. This enables together with the cooperative response to SM (ComX) a sharp transition in gene expression level and this without the SM dependent feedback loop. Due to its ultra-sensitive nature, the ComQXPA can operate at SM concentrations that are 100–1000 times lower than typically found in other QS systems, thereby substantially reducing the total metabolic cost of otherwise expensive ComX peptide.

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 Hierarchical Transcriptional Control of the LuxR Quorum-Sensing Regulon of Vibrio harveyi

2020 ◽  
Vol 202 (14) ◽  
Author(s):  
Ryan R. Chaparian ◽  
Alyssa S. Ball ◽  
Julia C. van Kessel
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Quorum Sensing ◽  
Cell Density ◽  
Regulatory Networks ◽  
Vibrio Harveyi ◽  
Sugar Transport ◽  
Content Type ◽  
Second Tier

ABSTRACT In vibrios, quorum sensing controls hundreds of genes that are required for cell density-specific behaviors including bioluminescence, biofilm formation, competence, secretion, and swarming motility. The central transcription factor in the quorum-sensing pathway is LuxR/HapR, which directly regulates ∼100 genes in the >400-gene regulon of Vibrio harveyi. Among these directly controlled genes are 15 transcription factors, which we predicted would comprise the second tier in the hierarchy of the LuxR regulon. We confirmed that LuxR binds to the promoters of these genes in vitro and quantified the extent of LuxR activation or repression of transcript levels. Transcriptome sequencing (RNA-seq) indicates that most of these transcriptional regulators control only a few genes, with the exception of MetJ, which is a global regulator. The genes regulated by these transcription factors are predicted to be involved in methionine and thiamine biosynthesis, membrane stability, RNA processing, c-di-GMP degradation, sugar transport, and other cellular processes. These data support a hierarchical model in which LuxR directly regulates 15 transcription factors that drive the second level of the gene expression cascade to influence cell density-dependent metabolic states and behaviors in V. harveyi. IMPORTANCE Quorum sensing is important for survival of bacteria in nature and influences the actions of bacterial groups. In the relatively few studied examples of quorum-sensing-controlled genes, these genes are associated with competition or cooperation in complex microbial communities and/or virulence in a host. However, quorum sensing in vibrios controls the expression of hundreds of genes, and their functions are mostly unknown or uncharacterized. In this study, we identify the regulators of the second tier of gene expression in the quorum-sensing system of the aquaculture pathogen Vibrio harveyi. Our identification of regulatory networks and metabolic pathways controlled by quorum sensing can be extended and compared to other Vibrio species to understand the physiology, ecology, and pathogenesis of these organisms.

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