scholarly journals Cell Density-Dependent Starvation Survival ofRhizobium leguminosarum bv. phaseoli: Identification of the Role of an N- Acyl Homoserine Lactone in Adaptation to Stationary-Phase Survival

1999 ◽  
Vol 181 (3) ◽  
pp. 981-990 ◽  
Author(s):  
Stephen H. Thorne ◽  
Huw D. Williams
Keyword(s):  
Stationary Phase ◽  
Cell Density ◽  
Rhizobium Leguminosarum ◽  
Homoserine Lactone ◽  
Growth Conditions ◽  
Acyl Homoserine Lactone ◽  
Density Dependent ◽  
Extracellular Factor ◽  
Stationary Phase Survival ◽  
Starvation Survival

ABSTRACT The cell density dependence of stationary-phase survival ofRhizobium leguminosarum has been investigated. Following starvation by exhaustion of carbon or nitrogen, but not of phosphorus, the survival of cultures was dependent on the cell density at entry into stationary phase. High-density cultures survived with little or no loss of viability over a 20-day period in stationary phase. In contrast, low-density cultures lost viability rapidly but consisted of a heterogeneous population, a small fraction of which successfully adapted and eventually formed a stable, surviving population. The threshold density above which the cultures survived successfully in stationary phase was dependent on the growth conditions and the strain used. We took advantage of the fact that R. leguminosarumsurvives poorly following starvation by resuspension in carbon-free medium to demonstrate that cell density-dependent survival was mediated by a component accumulating in the growth medium. The effects of this medium component on survival in resuspension assays could be mimicked by an N-acyl homoserine lactone,N-(3R-hydroxy-7-cis-tetradecanoyl)-l-homoserine lactone, previously demonstrated to have a role in controlling cell density-dependent phenomena in R. leguminosarum. The Sym plasmids pRP2JI and pRL1JI were found to be essential for the production of the extracellular factor, which could also be made inEscherichia coli carrying the cosmid clone pIJ1086 containing a specific region of pRL1JI.

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 Altered srf Expression in Bacillus subtilisResulting from Changes in Culture pH Is Dependent on the Spo0K Oligopeptide Permease and the ComQX System of Extracellular Control

1998 ◽  
Vol 180 (6) ◽  
pp. 1438-1445 ◽  
Author(s):  
W. Mark Cosby ◽  
Dirk Vollenbroich ◽  
Oh Hyoung Lee ◽  
Peter Zuber
Keyword(s):  
Cell Density ◽  
Regulatory Protein ◽  
Dependent Manner ◽  
Density Dependent ◽  
Culture Ph ◽  
Extracellular Factor ◽  
Ph Dependent ◽  
Surfactin Production ◽  
Oligopeptide Permease ◽  
Late Growth

ABSTRACT The expression of the srf operon of Bacillus subtilis, encoding surfactin synthetase and the competence regulatory protein ComS, was observed to be reduced when cells were grown in a rich glucose- and glutamine-containing medium in which late-growth culture pH was 5.0 or lower. The production of the surfactin synthetase subunits and of surfactin itself was also reduced. Raising the pH to near neutrality resulted in dramatic increases in srf expression and surfactin production. This apparent pH-dependent induction of srf expression requiredspo0K, which encodes the oligopeptide permease that functions in cell-density-dependent control of sporulation and competence, but not CSF, the competence-inducing pheromone that regulates srf expression in a Spo0K-dependent manner. Both ComP and ComA, the two-component regulatory pair that stimulates cell-density-dependent srf transcription, were required for optimal expression of srf at low and high pHs, but ComP was not required for pH-dependent srf induction. The known negative regulators of srf, RapC and CodY, were found not to function significantly in pH-dependent srf expression. Late-growth culture supernatants at low pH were not active in inducingsrf expression in cells of low-density cultures but were rendered active when their pH was raised to near neutrality. ComQ (and very likely the srf-inducing pheromone ComX) and Spo0K were found to be required for the extracellular induction ofsrf-lacZ at neutral pH. The results suggest thatsrf expression, in response to changes in culture pH, requires Spo0K and another, as yet unidentified, extracellular factor. The study also provides evidence consistent with the hypothesis that ComP acts both positively and negatively in the regulation of ComA and that both activities are controlled by the ComX pheromone.

scholarly journals Methylobacterium extorquensAM1 produces a novel type of acyl-homoserine lactone with a double unsaturated side chain under methylotrophic growth conditions

FEBS Letters ◽  
2005 ◽  
Vol 580 (2) ◽  
pp. 561-567 ◽  
Author(s):  
Carlos G. Nieto Penalver ◽  
Danièle Morin ◽  
Franck Cantet ◽  
Olivier Saurel ◽  
Alain Milon ◽  
...  
Keyword(s):  
Homoserine Lactone ◽  
Growth Conditions ◽  
Side Chain ◽  
Acyl Homoserine Lactone ◽  
Methylotrophic Growth

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 Biofilm Formation and Acyl Homoserine Lactone Production in the Burkholderia cepacia Complex

2002 ◽  
Vol 184 (20) ◽  
pp. 5678-5685 ◽  
Author(s):  
Barbara-Ann D. Conway ◽  
Vicnays Venu ◽  
David P. Speert
Keyword(s):  
Biofilm Formation ◽  
Burkholderia Cepacia ◽  
Luria Broth ◽  
Homoserine Lactone ◽  
Growth Conditions ◽  
Burkholderia Cepacia Complex ◽  
Acyl Homoserine Lactone ◽  
Cystic Fibrosis Isolate ◽  
Consistent Feature ◽  
Basal Salts

ABSTRACT Acyl homoserine lactone (acyl-HSL)-mediated gene regulation has been shown to influence biofilm formation in one Burkholderia cepacia cystic fibrosis isolate, but it is not known whether this relationship is a consistent feature of the several genomic species that make up the B. cepacia complex (BCC). We screened strains belonging to genomovars I to V of the BCC for biofilm formation on an abiotic surface and for acyl-HSL synthesis. We determined that organisms from each of these genomovars were capable of biofilm formation. Similarly, acyl-HSL was synthesized by organisms from each of genomovars I to V, with most isolates producing octanoyl-HSL in greatest abundance. When biofilms were grown in Luria broth, acyl-HSL synthesis and biofilm formation appeared to be associated, but these phenotypes were independent when the biofilms were grown in basal salts containing citrate. Genomovar V strains synthesized the greatest quantities of acyl-HSL, and genomovar II and III-A strains elaborated the most abundant biofilms. Quorum sensing may play a role in BCC pathogenesis, but it may not regulate biofilm formation under all growth conditions.

scholarly journals Identification, Timing, and Signal Specificity of Pseudomonas aeruginosa Quorum-Controlled Genes: a Transcriptome Analysis

2003 ◽  
Vol 185 (7) ◽  
pp. 2066-2079 ◽  
Author(s):  
Martin Schuster ◽  
C. Phoebe Lostroh ◽  
Tomoo Ogi ◽  
E. P. Greenberg
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Stationary Phase ◽  
Transcriptome Analysis ◽  
Homoserine Lactone ◽  
Logarithmic Phase ◽  
Acyl Homoserine Lactone ◽  
Global Regulators ◽  
Signaling Systems

ABSTRACT There are two interrelated acyl-homoserine lactone quorum-sensing-signaling systems in Pseudomonas aeruginosa. These systems, the LasR-LasI system and the RhlR-RhlI system, are global regulators of gene expression. We performed a transcriptome analysis to identify quorum-sensing-controlled genes and to better understand quorum-sensing control of P. aeruginosa gene expression. We compared gene expression in a LasI-RhlI signal mutant grown with added signals to gene expression without added signals, and we compared a LasR-RhlR signal receptor mutant to its parent. In all, we identified 315 quorum-induced and 38 quorum-repressed genes, representing about 6% of the P. aeruginosa genome. The quorum-repressed genes were activated in the stationary phase in quorum-sensing mutants but were not activated in the parent strain. The analysis of quorum-induced genes suggests that the signal specificities are on a continuum and that the timing of gene expression is on a continuum (some genes are induced early in growth, most genes are induced at the transition from the logarithmic phase to the stationary phase, and some genes are induced during the stationary phase). In general, timing was not related to signal concentration. We suggest that the level of the signal receptor, LasR, is a critical trigger for quorum-activated gene expression. Acyl-homoserine lactone quorum sensing appears to be a system that allows ordered expression of hundreds of genes during P. aeruginosa growth in culture.

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