scholarly journals RelA-Dependent (p)ppGpp Production Controls Exoenzyme Synthesis in Erwinia carotovora subsp. atroseptica

2007 ◽  
Vol 189 (21) ◽  
pp. 7643-7652 ◽  
Author(s):  
Jinhong Wang ◽  
Noemie Gardiol ◽  
Tom Burr ◽  
George P. C. Salmond ◽  
Martin Welch
Keyword(s):  
Quorum Sensing ◽  
Nutrient Limitation ◽  
Pectate Lyase ◽  
Erwinia Carotovora ◽  
Homoserine Lactone ◽  
Competitive Inhibitor ◽  
Pcr Analysis ◽  
Wild Type ◽  
Signal Molecule ◽  
Potent Inducer

ABSTRACT In this report, we investigate the link between nutrient limitation, RelA-mediated (p)ppGpp production, and virulence in the phytopathogen Erwinia carotovora subsp. atroseptica. A relA null mutant (JWC7) was constructed by allelic exchange, and we confirmed that, unlike the wild-type progenitor, this mutant did not produce elevated levels of (p)ppGpp upon nutrient downshift. However, (p)ppGpp production could be restored in strain JWC7 during nutrient limitation by supplying relA in trans. During growth on exoenzyme-inducing minimal medium, the relA mutant showed a diminution in secreted pectate lyase and protease activities and a severe defect in motility. The relA mutant was also impaired in its ability to cause rot in potato tubers. In the presence of serine hydroxamate (a competitive inhibitor of seryl tRNA synthase and a potent inducer of the stringent response in wild-type E. carotovora subsp. atroseptica), exoenzyme production was essentially abolished in JWC7 but could be restored in the presence of plasmid-borne relA. The inhibition of exoenzyme production in JWC7 caused by serine hydroxamate could not be overcome by addition of the quorum-sensing signal molecule, N-3-oxohexanoyl-l-homoserine lactone. Quantitative reverse transcription-PCR analysis of selected RNA species confirmed that the effects of relA on secreted pectate lyase activity and motility could be attributed to a reduction in transcription of the corresponding genes. We conclude that nutrient limitation is a potent environmental cue that triggers (p)ppGpp-dependent exoenzyme production in E. carotovora subsp. atroseptica. Furthermore, our data suggest that nutrient limitation [or rather, (p)ppGpp accumulation] is a prerequisite for effective quorum-sensing-dependent activation of exoenzyme production.

scholarly journals Transgenic Plants Producing the Bacterial Pheromone N-Acyl-Homoserine Lactone Exhibit Enhanced Resistance to the Bacterial Phytopathogen Erwinia carotovora

2001 ◽  
Vol 14 (9) ◽  
pp. 1035-1042 ◽  
Author(s):  
Andres Mäe ◽  
Marcos Montesano ◽  
Viia Koiv ◽  
E. Tapio Palva
Keyword(s):  
Quorum Sensing ◽  
Transgenic Tobacco ◽  
Plant Cell Wall ◽  
Ectopic Expression ◽  
Erwinia Carotovora ◽  
Homoserine Lactone ◽  
Defense Responses ◽  
Dependent Manner ◽  
Wild Type ◽  
Enhanced Resistance

Bacterial pheromones, mainly different homoserine lactones, are central to a number of bacterial signaling processes, including those involved in plant pathogenicity. We previously demonstrated that N-oxoacyl-homoserine lactone (OHL) is essential for quorum sensing in the soft-rot phytopathogen Erwinia carotovora. In this pathogen, OHL controls the coordinate activation of genes encoding the main virulence determinants, extracellular plant cell wall degrading enzymes (PCWDEs), in a cell density-dependent manner. We suggest that E. carotovora employ quorum sensing to avoid the premature production of PCWDEs and subsequent activation of plant defense responses. To test whether modulating this sensory system would affect the outcome of a plant-pathogen interaction, we generated transgenic tobacco, producing OHL. This was accomplished by ectopic expression in tobacco of the E. carotovora gene expI, which is responsible for OHL biosynthesis. We show that expI-positive transgenic tobacco lines produced the active pheromone and partially complemented the avirulent phenotype of expI mutants. The OHL-producing tobacco lines exhibited enhanced resistance to infection by wild-type E. carotovora. The results were confirmed by exogenous addition of OHL to wild-type plants, which also resulted in increased resistance to E. carotovora.

scholarly journals Elevated Temperature Enhances Virulence of Erwinia carotovora subsp. carotovora Strain EC153 to Plants and Stimulates Production of the Quorum Sensing Signal, N-Acyl Homoserine Lactone, and Extracellular Proteins

2005 ◽  
Vol 71 (8) ◽  
pp. 4655-4663 ◽  
Author(s):  
H. Hasegawa ◽  
A. Chatterjee ◽  
Y. Cui ◽  
A. K. Chatterjee
Keyword(s):  
Quorum Sensing ◽  
Extracellular Enzymes ◽  
Rna Binding ◽  
Elevated Temperatures ◽  
Pectate Lyase ◽  
Erwinia Carotovora ◽  
Homoserine Lactone ◽  
Extracellular Proteins ◽  
Acyl Homoserine Lactone ◽  
Tissue Maceration

ABSTRACT Erwinia carotovora subsp. atroseptica, E. carotovora subsp. betavasculorum, and E. carotovora subsp. carotovora produce high levels of extracellular enzymes, such as pectate lyase (Pel), polygalacturonase (Peh), cellulase (Cel), and protease (Prt), and the quorum-sensing signal N-acyl-homoserine lactone (AHL) at 28°C. However, the production of these enzymes and AHL by these bacteria is severely inhibited during growth at elevated temperatures (31.2°C for E. carotovora subsp. atroseptica and 34.5°C for E. carotovora subsp. betavasculorum and most E. carotovora subsp. carotovora strains). At elevated temperatures these bacteria produce high levels of RsmA, an RNA binding protein that promotes RNA decay. E. carotovora subsp. carotovora strain EC153 is an exception in that it produces higher levels of Pel, Peh, Cel, and Prt at 34.5°C than at 28°C. EC153 also causes extensive maceration of celery petioles and Chinese cabbage leaves at 34.5°C, which correlates with a higher growth rate and higher levels of rRNA and AHL. The lack of pectinase production by E. carotovora subsp. carotovora strain Ecc71 at 34.5°C limits the growth of this organism in plant tissues and consequently impairs its ability to cause tissue maceration. Comparative studies with ahlI (the gene encoding a putative AHL synthase), pel-1, and peh-1 transcripts documented that at 34.5°C the RNAs are more stable in EC153 than in Ecc71. Our data reveal that overall metabolic activity, AHL levels, and mRNA stability are responsible for the higher levels of extracellular protein production and the enhanced virulence of EC153 at 34.5°C compared to 28°C.

Quorum sensing in soft-rotting Erwinia carotovora

2005 ◽  
Author(s):  
◽  
Hiroaki Hasegawa
Keyword(s):  
Quorum Sensing ◽  
Rna Binding ◽  
Elevated Temperatures ◽  
Minor Component ◽  
Pectate Lyase ◽  
Erwinia Carotovora ◽  
Homoserine Lactone ◽  
Class Ii ◽  
Negative Regulator ◽  
Class I

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The soft-rotting E. carotovora subspecies (ssp.) produces effectors and an array ofextra cellular enzymes, including pectate lyase (Pel), polygalacturonase (Peh), cellulase (Cell) and protease (Prt) that are known or predicted to function as virulence and pathogenicity factors. The production of these exoproteins is activated by quorum sensing (QS)signal, N-acyl homoserine lactone (AHL). At elevated temperatures, however, a majority of E. c. ssp. atroseptica (Eca), betavasculorum (Ecb) and carotovora (Ecc) strains produce much reduced amounts of AHL as well as those exoproteins, and activate the production of a global negative regulator, RsmA (Rsm = regulator of secondarymetabolites). Ecc strain EC153 is an exception in that it produces higher levels of exproteins as well as AHL at 34.5[degree sign]C than at 28[degree sign]C. Temperature-dependent production of virrulence factors by these strains correlates with overall metabolic activities and stabilities of ahlI (the gene for AHL synthase), pel-1 and peh-1 transcripts. EC153 also causes extensive maceration of celery and Chinese cabbage petioles at 34.5[degree sign]C, which contrasts with limited tissue maceration by Ecc strain Ecc71 at this temperature. Thus, overall metabolic activity, higher levels of AHL and greater mRNA stability of virulence activates transcription of rsmA. This activation of rsmA is prevented by AHL. Consequently, in the presence of AHL RsmA production occurs at a low level, triggering the production of virulence factors. These findings for the first time document regulation of an RNA-binding protien by ExpR and AHL, link quorum sensing system via posttransciptional regulation, and explain the basis for the pleiotropic effects of AHL in Ecc. This study also reports the existence of two classes of strains based on structural and functional characteristics of ExpR and AhlI in Erwinia carotovora subspecies. While class I strains produce 3-oxooctanoyl-L-homoserine lactone (3-oxo-C8-HL) as the major AHL analog and 3-oxohexanoyl homoserine lactone (3-oxo-C6-HL) as a minor component, the members of class II strains produce 3-oxo-C6-HL as the major analog. It has also been found that AHL synthase is responsible for biosynthetic specificity. ExpR species do not discriminate between rsmA genes of strains belonging to the two classes. However, specificity is conferred by AHL analogs in that 3-oxo-C8-HL neutralizes the actions of class II ExpRs whereas 3-oxo-C6HL neutalizes class I ExpRs.

Ecbl and EcbR: homologs of Luxl and LuxR affecting antibiotic and exoenzyme production byErwinia carotovorasubsp.betavasculorum

1997 ◽  
Vol 43 (12) ◽  
pp. 1164-1171 ◽  
Author(s):  
José M. Costa ◽  
Joyce E. Loper
Keyword(s):  
Quorum Sensing ◽  
Antibiotic Production ◽  
Pectate Lyase ◽  
Erwinia Carotovora ◽  
Protease Production ◽  
Predicted Amino Acid Sequence ◽  
Wild Type ◽  
E Coli ◽  
Acylhomoserine Lactone ◽  
Lyase Activity

Erwinia carotovora subsp. betavasculorum Ecb168 causes vascular necrosis and root rot of sugar beet and produces an antibiotic(s) that is antagonistic against other Erwinia spp. EcbI−mutants of Ecb168, each containing a single transposon insertion in the ecbI gene (for Erwinia carotovora subsp. betavasculorum inducer), do not produce detectable levels of extracellular protease or antibiotic(s), and express less pectate lyase activity and virulence than the wild-type strain. A plasmid containing the cloned ecbI gene complemented the EcbI−mutants for these phenotypes. Protease production by EcbI−mutants grown on agar surfaces was restored by neighboring cells of Escherichia coli containing ecbI. Production of a diffusible N-acylhomoserine lactone autoinducer by wild-type Ecb168 was detected with indicator strains of E. coli and Agrobacterium tumefaciens. EcbI−mutant strains did not produce an autoinducer detected by the indicator strains. Antibiotic production by EcbI−mutants was restored by cell-free culture supernatants of Ecb168 or E. coli containing a cloned ecbI gene. The predicted amino acid sequence of EcbI is similar to those of CarI, ExpI, and HslI, three LuxI homologs required for production of a diffusible N-acylhomoserine lactone autoinducer in Erwinia carotovora subsp. carotovora. A luxR homolog, termed ecbR (for Erwinia carotovora subsp. betavasculorum regulator), is convergently transcribed and overlaps with ecbI by 17 bp at their 3′ ends. These results are consistent with the hypothesis that a quorum-sensing system related to the prototypic luxI–luxR gene pair controls antibiotic and exoenzyme production in Erwinia carotovora subsp. betavasculorum.Key words: quorum sensing, β-lactam, gene regulation.

scholarly journals Novel Quorum-Sensing-Controlled Genes in Erwinia carotovora subsp. carotovora: Identification of a Fungal Elicitor Homologue in a Soft-Rotting Bacterium

2005 ◽  
Vol 18 (4) ◽  
pp. 343-353 ◽  
Author(s):  
C. L. Pemberton ◽  
N. A. Whitehead ◽  
M. Sebaihia ◽  
K. S. Bell ◽  
L. J. Hyman ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Fusarium Oxysporum ◽  
Erwinia Carotovora ◽  
Homoserine Lactone ◽  
Stem Rot ◽  
Potato Tubers ◽  
Global Regulator ◽  
Signal Molecule ◽  
New Genes ◽  
Dicotyledonous Plants

Seven new genes controlled by the quorum-sensing signal molecule N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) have been identified in Erwinia carotovora subsp. carotovora. Using TnphoA as a mutagen, we enriched for mutants defective in proteins that could play a role in the interaction between E. carotovora subsp. carotovora and its plant hosts, and identified NipEcc and its counterpart in E. carotovora subsp. atroseptica. These are members of a growing family of proteins related to Nep1 from Fusarium oxysporum which can induce necrotic responses in a variety of dicotyledonous plants. NipEcc produced necrosis in tobacco, NipEca affected potato stem rot, and both affected virulence in potato tubers. In E. carotovora subsp. carotovora, nip was shown to be subject to weak repression by the LuxR family regulator, EccR, and may be regulated by the negative global regulator RsmA.

Detection of a quorum sensing signal molecule of Acidovorax avenae subsp. citrulli and its regulation of pathogenicity

2009 ◽  
Vol 6 (1) ◽  
pp. 49-53 ◽  
Author(s):  
Chen Tao ◽  
Qian Guo-Liang ◽  
Yang Xiao-Li ◽  
Ma Jun-Yi ◽  
Hu Bai-Shi ◽  
...  
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Acyl Homoserine Lactone ◽  
Wild Type ◽  
Signal Molecule ◽  
Bacterial Fruit Blotch

AbstractAn efficient AHL (N-acyl-homoserine lactone) bioassay strain, JZA1, of Agrobacterium tumefaciens was used to detect the AHL production from Acidovorax avenae subsp. citrulli [the pathogen causing bacterial fruit blotch (BFB) of melons], and the results showed that A. avenae subsp. citrulli produced a 3-O-C8-homoserine (HSL) type signal molecule. Gene aiiA, which could degrade AHL molecules, was transformed into A. avenae subsp. citrulli strain NJF10, creating strain NJF10-aiiA. The AHL production from NJF10-aiiA was significantly reduced compared with wild-type NJF10. Inoculation tests showed that NJF10-aiiA had an obvious reduction of virulence on watermelon fruits. Our finds showed that AHL production by A. avenae subsp. citrulli was related to its pathogenicity. This work might provide a novel way to control BFB by QS (quorum sensing) interference.

Optimization of Vibrio harveyi Luminometry Assay for Detecting Quorum Sensing Inhibitors

2005 ◽  
Vol 277-279 ◽  
pp. 19-22
Author(s):  
Yeon Hee Kim ◽  
Y. Kim ◽  
Sung Hoon Park ◽  
Jung Sun Kim
Keyword(s):  
Quorum Sensing ◽  
Vibrio Harveyi ◽  
Homoserine Lactone ◽  
Dependent Manner ◽  
Wild Type ◽  
Signal Molecule ◽  
Homoserine Lactones ◽  
Quorum Sensing Inhibitors ◽  
Chain Lengths ◽  
Dose Dependent

The luminometry assay using the wild-type Vibrio harveyi BB120 was evaluated as a possible detection method for quorum sensing inhibitors. The effects of the concentration of the quorum sensing signal molecule (AHL) as well as the cell density of the reporter strain and the different AHL analogues on luminescence expressed as relative light units (RLU) were examined. Inhibition of V. harveyi luminescence was observed in a dose dependent manner for all five AHL analogues. The RLU values exhibited linearity within the range of 2.9 x 102 ~ 3.2 x 105. Detection up to 102nM was possible for dodecanoyl-homoserine lactone and AHLs with alkyl chain lengths of C-8~C-14 were more active than the shorter chain-lengthed hexanoyl-homoserine lactones. Lipophilicity of the AHL seems to affect the sensitivity of the assay.

scholarly journals N-3-Hydroxy Dodecanoyl-DL-homoserine Lactone (OH-dDHL) Triggers Apoptosis of Bone Marrow-Derived Macrophages through the ER- and Mitochondria-Mediated Pathways

2021 ◽  
Vol 22 (14) ◽  
pp. 7565
Author(s):  
Kyungho Woo ◽  
Dong Ho Kim ◽  
Man Hwan Oh ◽  
Ho Sung Park ◽  
Chul Hee Choi
Keyword(s):  
Bone Marrow ◽  
Quorum Sensing ◽  
Deletion Mutant ◽  
Transmembrane Protein ◽  
Cell Communication ◽  
Homoserine Lactone ◽  
Host Responses ◽  
Wild Type ◽  
Mutant Strains

Quorum sensing of Acinetobacter nosocomialis for cell-to-cell communication produces N-3-hydroxy dodecanoyl-DL-homoserine lactone (OH-dDHL) by an AnoR/I two-component system. However, OH-dDHL-driven apoptotic mechanisms in hosts have not been clearly defined. Here, we investigated the induction of apoptosis signaling pathways in bone marrow-derived macrophages treated with synthetic OH-dDHL. Moreover, the quorum-sensing system for virulence regulation was evaluated in vivo using wild-type and anoI-deletion mutant strains. OH-dDHL decreased the viability of macrophage and epithelial cells in dose- and time-dependent manners. OH-dDHL induced Ca2+ efflux and caspase-12 activation by ER stress transmembrane protein (IRE1 and ATF6a p50) aggregation and induced mitochondrial dysfunction through reactive oxygen species (ROS) production, which caused cytochrome c to leak. Pretreatment with a pan-caspase inhibitor reduced caspase-3, -8, and -9, which were activated by OH-dDHL. Pro-inflammatory cytokine and paraoxonase-2 (PON2) gene expression were increased by OH-dDHL. We showed that the anoI-deletion mutant strains have less intracellular invasion compared to the wild-type strain, and their virulence, such as colonization and dissemination, was decreased in vivo. Consequently, these findings revealed that OH-dDHL, as a virulence factor, contributes to bacterial infection and survival as well as the modification of host responses in the early stages of infection.

scholarly journals Quorum Sensing: a Transcriptional Regulatory System Involved in the Pathogenicity of Burkholderia mallei

2004 ◽  
Vol 72 (11) ◽  
pp. 6589-6596 ◽  
Author(s):  
Ricky L. Ulrich ◽  
David DeShazer ◽  
Harry B. Hines ◽  
Jeffrey A. Jeddeloh
Keyword(s):  
Quorum Sensing ◽  
Virulence Factor ◽  
Regulatory System ◽  
In Silico Analysis ◽  
Homoserine Lactone ◽  
Burkholderia Mallei ◽  
Wild Type ◽  
Transcriptional Regulatory ◽  
A Cell

ABSTRACT Numerous gram-negative bacterial pathogens regulate virulence factor expression by using a cell density mechanism termed quorum sensing (QS). An in silico analysis of the Burkholderia mallei ATCC 23344 genome revealed that it encodes at least two luxI and four luxR homologues. Using mass spectrometry, we showed that wild-type B. mallei produces the signaling molecules N-octanoyl-homoserine lactone and N-decanoyl-homoserine lactone. To determine if QS is involved in the virulence of B. mallei, we generated mutations in each putative luxIR homologue and tested the pathogenicities of the derivative strains in aerosol BALB/c mouse and intraperitoneal hamster models. Disruption of the B. mallei QS alleles, especially in RJ16 (bmaII) and RJ17 (bmaI3), which are luxI mutants, significantly reduced virulence, as indicated by the survival of mice who were aerosolized with 104 CFU (10 50% lethal doses [LD50s]). For the B. mallei transcriptional regulator mutants (luxR homologues), mutation of the bmaR5 allele resulted in the most pronounced decrease in virulence, with 100% of the challenged animals surviving a dose of 10 LD50s. Using a Syrian hamster intraperitoneal model of infection, we determined the LD50s for wild-type B. mallei and each QS mutant. An increase in the relative LD50 was found for RJ16 (bmaI1) (>967 CFU), RJ17 (bmaI3) (115 CFU), and RJ20 (bmaR5) (151 CFU) compared to wild-type B. mallei (<13 CFU). These findings demonstrate that B. mallei carries multiple luxIR homologues that either directly or indirectly regulate the biosynthesis of an essential virulence factor(s) that contributes to the pathogenicity of B. mallei in vivo.

scholarly journals Inhibition of Quorum Sensing in Serratia marcescens AS-1 by Synthetic Analogs of N-Acylhomoserine Lactone

2007 ◽  
Vol 73 (20) ◽  
pp. 6339-6344 ◽  
Author(s):  
Tomohiro Morohoshi ◽  
Toshitaka Shiono ◽  
Kiyomi Takidouchi ◽  
Masashi Kato ◽  
Norihiro Kato ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Serratia Marcescens ◽  
Biofilm Formation ◽  
Acyl Chain ◽  
Regulatory System ◽  
Homoserine Lactone ◽  
Signal Molecule ◽  
Swarming Motility ◽  
Gram Negative ◽  
Acylhomoserine Lactone

ABSTRACT Quorum sensing is a regulatory system for controlling gene expression in response to increasing cell density. N-Acylhomoserine lactone (AHL) is produced by gram-negative bacteria, which use it as a quorum-sensing signal molecule. Serratia marcescens is a gram-negative opportunistic pathogen which is responsible for an increasing number of serious nosocomial infections. S. marcescens AS-1 produces N-hexanoyl homoserine lactone (C6-HSL) and N-(3-oxohexanoyl) homoserine lactone and regulates prodigiosin production, swarming motility, and biofilm formation by AHL-mediated quorum sensing. We synthesized a series of N-acyl cyclopentylamides with acyl chain lengths ranging from 4 to 12 and estimated their inhibitory effects on prodigiosin production in AS-1. One of these molecules, N-nonanoyl-cyclopentylamide (C9-CPA), had a strong inhibitory effect on prodigiosin production. C9-CPA also inhibited the swarming motility and biofilm formation of AS-1. A competition assay revealed that C9-CPA was able to inhibit quorum sensing at four times the concentration of exogenous C6-HSL and was more effective than the previously reported halogenated furanone. Our results demonstrated that C9-CPA was an effective quorum-sensing inhibitor for S. marcescens AS-1.

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