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Sample records for acylhomoserine lactones ahls

  1. Improvement of bioelectrochemical property and energy recovery by acylhomoserine lactones (AHLs) in microbial electrolysis cells (MECs)

    NASA Astrophysics Data System (ADS)

    Liu, Wenzong; Cai, Weiwei; Ma, Anzhou; Ren, Ge; Li, Zhiling; Zhuang, Guoqiang; Wang, Aijie

    2015-06-01

    Quorum sensing (QS) has been extensively studied as a cell-cell communication system, where small chemical signal molecules (acylhomoserine lactones, AHLs) can regulate the bacterial communications in bioelectrochemical systems via chemical signaling and electric signaling. In this study, electrochemical activity of bio-anode is substantially promoted by adding two kinds of AHLs with different chain length at the stage of community formation in microbial electrolysis cells (MECs). Hydrogen yield increase is observed by adding of two chain length AHLs, 3-oxo-hexanoyl-homoserine lactone (3OC6-HSL) and 3-oxo-dodecanoyl homoserine lactone (3OC12-HSL). A higher MEC current is acquired with addition of 3OC6-HSL than 3OC12-HSL at a fixed voltage of 0.8 V (vs. SHE). The highest yield is up to 3.8 ± 0.2 mol H2 mol-1 acetate at 10 μM 3OC6-HSL, which is increased 29% over control MECs. Evaluated on applied voltage, energy efficiency is increased to 171.6 ± 21.3% with short chain AHL, however, no significant improvement is performed on energy efficiency and coulombic efficiency with long-chain AHL. The study shows that bioelectrochemical characteristics of MECs varied on the chain length of AHL signal molecules and short-chain AHLs have a more positive effect on electron transfer and energy recovery in MECs.

  2. Diversity and Distribution of N-Acylhomoserine Lactone (AHL)-Degrading Activity and AHL-Lactonase (AiiM) in Genus Microbacterium

    PubMed Central

    Wang, Wen-Zhao; Morohoshi, Tomohiro; Someya, Nobutaka; Ikeda, Tsukasa

    2012-01-01

    N-Acylhomoserine lactone (AHL)-degrading enzyme, AiiM, was identified from the potato leaf-associated Microbacterium testaceum StLB037. In this study, we cloned eight aiiM gene homologues from other AHL-degrading Microbacterium strains. The similarity of the chromosomal locus of the aiiM gene is associated with the phylogenetic classification based on 16S rRNA. Degenerate PCR revealed that the aiiM gene was only conserved in AHL-degrading Microbacterium strains, but not in fifteen Microbacterium type strains or two Microbacterium isolates from other plants. These results suggested that the high level of AHL-degrading activity in Microbacterium strains was caused by the aiiM gene encoded on their chromosome. PMID:22446311

  3. Defining the structure and function of acyl-homoserine lactone autoinducers

    PubMed Central

    Churchill, Mair E.A.; Sibhatu, Hiruy M.; Uhlson, Charis L.

    2012-01-01

    Quorum sensing plays a central role in regulating many community derived symbiotic and pathogenic relationships of bacteria, and as such has attracted much attention in recent years. Acyl-homoserine lactones (AHLs) are important signaling molecules in the quorum sensing gene regulatory processes found in numerous gram-negative species of bacteria that interact with eukaryotic organisms. AHLs are produced by acyl-homoserine lactone synthases. Bacteria can have multiple genes for AHL synthase enzymes, and such species are likely to produce several different types of AHLs. Determination of the types and the relative amounts of AHLs produced by AHL synthases in bacteria under varied conditions provides important insights into the mechanism of AHL synthase function and the regulation of transcriptional cascades initiated by quorum sensing signaling. This chapter describes a mass spectrometry method for determining the types and relative amounts of AHLs present in a sample. PMID:21031311

  4. Defining the structure and function of acyl-homoserine lactone autoinducers.

    PubMed

    Churchill, Mair E A; Sibhatu, Hiruy M; Uhlson, Charis L

    2011-01-01

    Quorum sensing plays a central role in regulating many community-derived symbiotic and pathogenic relationships of bacteria, and as such has attracted much attention in recent years. Acyl-homoserine lactones (AHLs) are important signaling molecules in the quorum sensing gene-regulatory processes found in numerous gram-negative species of bacteria that interact with eukaryotic organisms. AHLs are produced by acyl-homoserine lactone synthases. Bacteria can have multiple genes for AHL synthase enzymes, and such species are likely to produce several different types of AHLs. Determination of the types and the relative amounts of AHLs produced by AHL synthases in bacteria under varied conditions provides important insights into the mechanism of AHL synthase function and the regulation of transcriptional cascades initiated by quorum sensing signaling. This chapter describes a mass spectrometry method for determining the types and relative amounts of AHLs present in a sample.

  5. AhlD, an N-acylhomoserine lactonase in Arthrobacter sp., and predicted homologues in other bacteria.

    PubMed

    Park, Sun-Yang; Lee, Sang Jun; Oh, Tae-Kwang; Oh, Jong-Won; Koo, Bon-Tag; Yum, Do-Young; Lee, Jung-Kee

    2003-06-01

    Quorum sensing is a signalling mechanism that controls diverse biological functions, including virulence, via N-acylhomoserine lactone (AHL) signal molecules in Gram-negative bacteria. With the aim of isolating strains or enzymes capable of blocking quorum sensing by inactivating AHL, bacteria were screened for AHL degradation by their ability to utilize N-3-oxohexanoyl-L-homoserine lactone (OHHL) as the sole carbon source. Among four isolates, strain IBN110, identified as Arthrobacter sp., was found to grow rapidly on OHHL, and to degrade various AHLs with different lengths and acyl side-chain substitutions. Co-culture of Arthrobacter sp. IBN110 and the plant pathogen Erwinia carotovora significantly reduced both the AHL amount and pectate lyase activity in co-culture medium, suggesting the possibility of applying Arthrobacter sp. IBN110 in the control of AHL-producing pathogenic bacteria. The ahlD gene from Arthrobacter sp. IBN110 encoding the enzyme catalysing AHL degradation was cloned, and found to encode a protein of 273 amino acids. A mass spectrometry analysis showed that AhlD probably hydrolyses the lactone ring of N-3-hexanoyl-L-homoserine lactone, indicating that AhlD is an N-acylhomoserine lactonase (AHLase). A comparison of AhlD with other known AHL-degrading enzymes, Bacillus sp. 240B1 AiiA, a Bacillus thuringiensis subsp. kyushuensis AiiA homologue and Agrobacterium tumefaciens AttM, revealed 25, 26 and 21 % overall identities, respectively, in the deduced amino acid sequences. Although these identities were relatively low, the HXDH approximately H approximately D motif was conserved in all the AHLases, suggesting that this motif is essential for AHLase activity. From a genome database search based on the conserved motif, putative AhlD-like lactonase genes were found in several other bacteria, and AHL-degrading activities were observed in Klebsiella pneumoniae and Bacillus stearothermophilus. Furthermore, it was verified that ahlK, an ahlD homologue

  6. Facilitating Cytokine-Mediated Cancer Cell Death by Proteobacterial N-Acylhomoserine Lactones

    PubMed Central

    Kravchenko, Vladimir; Garner, Amanda L.; Mathison, John; Seit-Nebi, Alim; Yu, Jing; Gileva, Irina P.; Ulevitch, Richard; Janda, Kim D.

    2013-01-01

    Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) preferentially induces apoptosis in cancer cells over normal cells; however, tumor cells may develop TRAIL resistance. Here we demonstrate that this resistance can be overcome in the presence of bacterial acylhomoserine lactones (AHLs) or AHL-producing bacteria through the combined effect of TRAIL-induced apoptosis and AHL-mediated inhibition of inflammation regulated by NF-κB signaling. This discovery unveils a previously unrecognized symbiotic link between bacteria and host immunosurveillance. PMID:23517377

  7. Acyl-homoserine lactones suppresses IEC-6 cell proliferation and increase permeability of isolated rat colon.

    PubMed

    Joe, Ga-Hyun; Andoh, Midori; Nomura, Mikako; Iwaya, Hitoshi; Lee, Jae-Sung; Shimizu, Hidehisa; Tsuji, Youhei; Maseda, Hideaki; Miyazaki, Hitoshi; Hara, Hiroshi; Ishizuka, Satoshi

    2014-01-01

    We investigated to determine whether a variety of acyl-homoserine lactones (AHLs) influences epithelial cell proliferation and mucosal permeability. 3-Oxo-C12-homoserine lactone (HSL) and 3-oxo-C14-HSL significantly suppressed IEC-6 cell proliferation. A significant increase in mucosal permeability was observed in isolated rat colon tissue exposed to C12-HSL, 3-oxo-C12-HSL, and 3-oxo-C14-HSL. These data indicate that AHLs suppress epithelial proliferation and disrupt barrier function in intestinal mucosa.

  8. Characterization of N-Acylhomoserine Lactones Produced by Bacteria Isolated from Industrial Cooling Water Systems.

    PubMed

    Okutsu, Noriya; Morohoshi, Tomohiro; Xie, Xiaonan; Kato, Norihiro; Ikeda, Tsukasa

    2015-12-30

    The cooling water systems are used to remove heat generated in the various industries. Biofouling of the cooling water systems causes blocking of condenser pipes and the heat exchanger tubes. In many Gram-negative bacteria, N-acylhomoserine lactone (AHL) are used as quorum-sensing signal molecule and associated with biofilm formation. To investigate the relationship between quorum sensing and biofouling in the cooling water system, we isolated a total of 192 bacterial strains from the five cooling water systems, and screened for AHL production. Seven isolates stimulated AHL-mediated purple pigment production in AHL reporter strain Chromobacterium violaceum CV026 or VIR07. Based on their 16S rRNA gene sequences, AHL-producing isolates were assigned to Aeromonas hydrophila, Lysobacter sp., Methylobacterium oryzae, and Bosea massiliensis. To the best of our knowledge, B. massiliensis and Lysobacter sp. have not been reported as AHL-producing species in the previous researches. AHLs extracted from the culture supernatants of B. massiliensis and Lysobacter sp. were identified by liquid chromatography-mass spectrometry. AHLs produced by B. massiliensis were assigned as N-hexanoyl-L-homoserine lactone (C6-HSL), N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL), and N-(3-oxooctanoyl)-L-homoserine lactone (3-oxo-C8-HSL). AHLs produced by Lysobacter sp. were assigned as N-decanoyl-L-homoserine lactone (C10-HSL) and N-(3-oxodecanoyl)-L-homoserine lactone (3-oxo-C10-HSL). This is the first report of identification of AHLs produced by B. massiliensis and Lysobacter sp. isolated from the cooling water system.

  9. Presence of acyl-homoserine lactones in 57 members of the Vibrionaceae family.

    PubMed

    Purohit, A A; Johansen, J A; Hansen, H; Leiros, H-K S; Kashulin, A; Karlsen, C; Smalås, A; Haugen, P; Willassen, N P

    2013-09-01

    The aim of this study was to use a sensitive method to screen and quantify 57 Vibrionaceae strains for the production of acyl-homoserine lactones (AHLs) and map the resulting AHL profiles onto a host phylogeny. We used a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) protocol to measure AHLs in spent media after bacterial growth. First, the presence/absence of AHLs (qualitative analysis) was measured to choose internal standard for subsequent quantitative AHL measurements. We screened 57 strains from three genera (Aliivibrio, Photobacterium and Vibrio) of the same family (i.e. Vibrionaceae). Our results show that about half of the isolates produced multiple AHLs, typically at 25-5000 nmol l(-1) . This work shows that production of AHL quorum sensing signals is found widespread among Vibrionaceae bacteria and that closely related strains typically produce similar AHL profiles. The AHL detection protocol presented in this study can be applied to a broad range of bacterial samples and may contribute to a wider mapping of AHL production in bacteria, for example, in clinically relevant strains. © 2013 The Authors. Journal of Applied Microbiology published by Wiley & Sons Ltd on behalf of Society for Applied Microbiology.

  10. Microbial metabolism of quorum-sensing molecules acyl-homoserine lactones, γ-heptalactone and other lactones.

    PubMed

    Safari, Maryam; Amache, Rana; Esmaeilishirazifard, Elham; Keshavarz, Tajalli

    2014-04-01

    The cell-to-cell communication of microorganisms is known to be via exertion of certain chemical compounds (signal molecules) and is referred to as quorum sensing (QS). QS phenomenon is widespread in microbial communities. Several Gram-positive and Gram-negative bacteria and fungi use lactone-containing compounds (e.g. acyl-homoserine lactones (AHLs), γ-heptalactone, butyrolactone-I) as signalling molecules. The ability of microorganisms to metabolise these compounds and the mechanisms they employ for this purpose are not clearly understood. Many studies, however, have focused on identifying AHL and other lactone-degrading enzymes produced by bacteria and fungi. Various strains that are able to utilise these signalling molecules as carbon and energy sources have also been isolated. In addition, several reports have provided evidence on the involvement of lactones and lactone-degrading enzymes in numerous biological functions. These studies, although focused on processes other than metabolism of lactone signalling molecules, still provide insights into further understanding of the mechanisms employed by various microorganisms to metabolise the QS compounds. In this review, we consider conceivable microbial strategies to metabolise AHL and other lactone-containing signalling molecules such as γ-heptalactones.

  11. Identification and characterization of N-acylhomoserine lactone-acylase from the fish intestinal Shewanella sp. strain MIB015.

    PubMed

    Morohoshi, Tomohiro; Nakazawa, Shigehisa; Ebata, Atsushi; Kato, Norihiro; Ikeda, Tsukasa

    2008-07-01

    N-Acylhomoserine lactones (AHLs) are used as quorum-sensing signal molecules by many gram-negative bacteria. We have reported that Shewanella sp. strain MIB015 degrades AHLs. In the present study, we cloned the aac gene from MIB015 by PCR with specific primers based on the aac gene in Shewanella oneidensis strain MR-1, which showed high homology with the known AHL-acylases. Escherichia coli expressing Aac showed high degrading activity of AHLs with long acyl chains. HPLC analysis revealed that Aac worked as AHL-acylase, which hydrolyzed the amide bond of AHL. In addition, expression of Aac in fish pathogen Vibrio anguillarum markedly reduced AHL production and biofilm formation. In conclusion, this study indicates that Aac might be effective in quenching quorum sensing of fish pathogens.

  12. Quorum Quenching: Enzymatic Disruption of N-Acylhomoserine Lactone-Mediated Bacterial Communication in Burkholderia thailandensis

    PubMed Central

    Ulrich, Ricky L.

    2004-01-01

    Many species of gram-negative bacteria communicate by synthesizing, secreting, and responding to N-acylhomoserine lactones (AHLs), a mechanism termed quorum sensing. Several investigations have characterized numerous AHL-degrading enzymes (AiiA lactonases) encoded by environmental isolates of Bacillus spp. The Burkholderia thailandensis quorum system is comprised of at least three AHL synthases (AHSs) and five transcriptional regulators belonging to the LuxIR class of proteins. Expression of the Bacillus anthracis (Ames strain) AiiA lactonase in B. thailandensis completely abolished the accumulation of N-decanoylhomoserine lactone (C10-HSL) and N-octanoylhomoserine lactone (C8-HSL), reduced N-hexanoylhomoserine lactone (C6-HSL) levels, altered both swarming and twitching motility, caused a significant increase in generation time, and affected carbon metabolism. In contrast, heterologous expression of the Bacillus cereus strain A24 AiiA lactonase in B. thailandensis reduced the concentrations of C6-HSL, C8-HSL, and C10-HSL to nondetectable levels; altered both swarming and twitching motility; and caused fluctuations in carbon utilization. Individual disruption of the B. thailandensis AHSs, specifically disruption of the btaI1 and btaI3 genes, which encode the proteins that direct the synthesis of C8-HSL and C6-HSL, respectively, caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates. In contrast, AHL cleavage in B. thailandensis by the Bacillus AiiA lactonases failed to enhance beta-hemolytic activity. The results of this study demonstrate that heterologous expression of Bacillus sp. AiiA lactonases in B. thailandensis reduced AHL accumulation, affected both swarming and twitching motility, increased generation time, altered substrate utilization, and prevented the beta-hemolysis of sheep erythrocytes. PMID:15466564

  13. Quorum quenching: enzymatic disruption of N-acylhomoserine lactone-mediated bacterial communication in Burkholderia thailandensis.

    PubMed

    Ulrich, Ricky L

    2004-10-01

    Many species of gram-negative bacteria communicate by synthesizing, secreting, and responding to N-acylhomoserine lactones (AHLs), a mechanism termed quorum sensing. Several investigations have characterized numerous AHL-degrading enzymes (AiiA lactonases) encoded by environmental isolates of Bacillus spp. The Burkholderia thailandensis quorum system is comprised of at least three AHL synthases (AHSs) and five transcriptional regulators belonging to the LuxIR class of proteins. Expression of the Bacillus anthracis (Ames strain) AiiA lactonase in B. thailandensis completely abolished the accumulation of N-decanoylhomoserine lactone (C(10)-HSL) and N-octanoylhomoserine lactone (C(8)-HSL), reduced N-hexanoylhomoserine lactone (C(6)-HSL) levels, altered both swarming and twitching motility, caused a significant increase in generation time, and affected carbon metabolism. In contrast, heterologous expression of the Bacillus cereus strain A24 AiiA lactonase in B. thailandensis reduced the concentrations of C(6)-HSL, C(8)-HSL, and C(10)-HSL to nondetectable levels; altered both swarming and twitching motility; and caused fluctuations in carbon utilization. Individual disruption of the B. thailandensis AHSs, specifically disruption of the btaI1 and btaI3 genes, which encode the proteins that direct the synthesis of C(8)-HSL and C(6)-HSL, respectively, caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates. In contrast, AHL cleavage in B. thailandensis by the Bacillus AiiA lactonases failed to enhance beta-hemolytic activity. The results of this study demonstrate that heterologous expression of Bacillus sp. AiiA lactonases in B. thailandensis reduced AHL accumulation, affected both swarming and twitching motility, increased generation time, altered substrate utilization, and prevented the beta-hemolysis of sheep erythrocytes.

  14. Quorum sensing and Chromobacterium violaceum: exploitation of violacein production and inhibition for the detection of N-acylhomoserine lactones.

    PubMed

    McClean, K H; Winson, M K; Fish, L; Taylor, A; Chhabra, S R; Camara, M; Daykin, M; Lamb, J H; Swift, S; Bycroft, B W; Stewart, G S; Williams, P

    1997-12-01

    Quorum sensing relies upon the interaction of a diffusible signal molecule with a transcriptional activator protein to couple gene expression with cell population density. In Gram-negative bacteria, such signal molecules are usually N-acylhomoserine lactones (AHLs) which differ in the structure of their N-acyl side chains. Chromobacterium violaceum, a Gram-negative bacterium commonly found in soil and water, produces the characteristic purple pigment violacein. Previously the authors described a violacein-negative, mini-Tn5 mutant of C. violaceum (CV026) in which pigment production can be restored by incubation with supernatants from the wild-type strain. To develop this mutant as a general biosensor for AHLs, the natural C. violaceum AHL molecule was first chemically characterized. By using solvent extraction, HPLC and mass spectrometry, a single AHL, N-hexanoyl-L-homoserine lactone (HHL), was identified in wild-type C. violaceum culture supernatants which was absent from CV026. Since the production of violacein constitutes a simple assay for the detection of AHLs, we explored the ability of CV026 to respond to a series of synthetic AHL and N-acylhomocysteine thiolactone (AHT) analogues. In CV026, violacein is inducible by all the AHL and AHT compounds evaluated with N-acyl side chains from C4 to C8 in length, with varying degrees of sensitivity. Although AHL compounds with N-acyl side chains from C10 to C14 are unable to induce violacein production, if an activating AHL (e.g. HHL) is incorporated into the agar, these long-chain AHLs can be detected by their ability to inhibit violacein production. The versatility of CV026 in facilitating detection of AHL mixtures extracted from culture supernatants and separated by thin-layer chromatography is also demonstrated. These simple bioassays employing CV026 thus greatly extend the ability to detect a wide spectrum of AHL signal molecules.

  15. Unusual Multiple Production of N-Acylhomoserine Lactones a by Burkholderia sp. Strain C10B Isolated from Dentine Caries

    PubMed Central

    Goh, Share Yuan; Tan, Wen-Si; Khan, Saad Ahmed; Chew, Hooi Pin; Kasim, Noor Hayaty Abu; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Bacteria realize the ability to communicate by production of quorum sensing (QS) molecules called autoinducers, which regulate the physiological activities in their ecological niches. The oral cavity could be a potential area for the presence of QS bacteria. In this study, we report the isolation of a QS bacterial isolate C10B from dentine caries. Preliminary screening using Chromobacterium violaceum CV026 biosensor showed that isolate C10B was able to produce N-acylhomoserine lactones (AHLs). This bacterium was further identified as a member of Burkholderia, an opportunistic pathogen. The isolated Burkholderia sp. was confirmed to produce N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL), N-decanoyl-L-homoserine lactone (C10-HSL) and N-dodecanoyl-L-homoserine lactone (C12-HSL). PMID:24854358

  16. Production of the quorum-sensing molecules N-acylhomoserine lactones by endobacteria associated with Mortierella alpina A-178.

    PubMed

    Kai, Kenji; Furuyabu, Kana; Tani, Ayaka; Hayashi, Hideo

    2012-08-13

    Gram-negative bacteria communicate with one another using N-acylhomoserine lactones (AHLs) as signaling molecules. This mechanism, known as quorum sensing (QS), is needed to develop pathogenicity, as well as symbiotic interactions with eukaryotic hosts, such as animals and plants. Increasing evidence indicates that certain bacteria, namely endobacteria, also inhabit fungal cells and establish symbiotic relationships with their hosts. However, it has not been clear whether bacterial QS acts in developing the relationships. Here we describe the isolation and identification of N-heptanoylhomoserine lactone and N-octanoylhomoserine lactone from the culture broth of the zygomycete fungus Mortierella alpina A-178. This suggested the presence of endobacteria in the fungus, as was confirmed by PCR, fluorescence in situ hybridization, and transmission electron microscopy. Two major bands obtained by PCR-denaturing gradient gel electrophoresis showed sequence identity to genes in the β-proteobacterium Castellaniella defragrans (100 %) and the Gram-positive bacterium Cryobacterium sp. (99.8 %). The production of AHLs depended on the presence of endobacteria and was induced in response to the increase in the concentration of AHLs, suggesting that the bacterium conducts AHL-mediated QS in the fungus. This paper is the first to report the production of AHLs by endofungal bacteria and raises the possibility that QS plays roles in the development of fungus-endobacterium symbiosis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Characteristics of N-Acylhomoserine Lactones Produced by Hafnia alvei H4 Isolated from Spoiled Instant Sea Cucumber.

    PubMed

    Hou, Hong-Man; Zhu, Yao-Lei; Wang, Jia-Ying; Jiang, Feng; Qu, Wen-Yan; Zhang, Gong-Liang; Hao, Hong-Shun

    2017-04-05

    This study aimed to identify N-acylhomoserine lactone (AHL) produced by Hafnia alvei H4, which was isolated from spoiled instant sea cucumber, and to investigate the effect of AHLs on biofilm formation. Two biosensor strains, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens KYC55, were used to detect the quorum sensing (QS) activity of H. alvei H4 and to confirm the existence of AHL-mediated QS system. Thin layer chromatography (TLC) and high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) analysis of the AHLs extracted from the culture supernatant of H. alvei H4 revealed the existence of at least three AHLs: N-hexanoyl-l-homoserine lactone (C6-HSL), N-(3-oxo-octanoyl)-l-homoserine lactone (3-oxo-C8-HSL), and N-butyryl-l-homoserine lactone (C4-HSL). This is the first report of the production of C4-HSL by H. alvei. In order to determine the relationship between the production of AHL by H. alvei H4 and bacterial growth, the β-galactosidase assay was employed to monitor AHL activity during a 48-h growth phase. AHLs production reached a maximum level of 134.6 Miller unites at late log phase (after 18 h) and then decreased to a stable level of about 100 Miller unites. AHL production and bacterial growth displayed a similar trend, suggesting that growth of H. alvei H4 might be regulated by QS. The effect of AHLs on biofilm formation of H. alvei H4 was investigated by adding exogenous AHLs (C4-HSL, C6-HSL and 3-oxo-C8-HSL) to H. alvei H4 culture. Biofilm formation was significantly promoted (p < 0.05) by 5 and 10 µM C6-HSL, inhibited (p < 0.05) by C4-HSL (5 and 10 µM) and 5 µM 3-oxo-C8-HSL, suggesting that QS may have a regulatory role in the biofilm formation of H. alvei H4.

  18. Penicillin V acylases from gram-negative bacteria degrade N-acylhomoserine lactones and attenuate virulence in Pseudomonas aeruginosa.

    PubMed

    Sunder, Avinash Vellore; Utari, Putri Dwi; Ramasamy, Sureshkumar; van Merkerk, Ronald; Quax, Wim; Pundle, Archana

    2017-03-01

    Virulence pathways in gram-negative pathogenic bacteria are regulated by quorum sensing mechanisms, through the production and sensing of N-acylhomoserine lactone (AHL) signal molecules. Enzymatic degradation of AHLs leading to attenuation of virulence (quorum quenching) could pave the way for the development of new antibacterials. Penicillin V acylases (PVAs) belong to the Ntn hydrolase superfamily, together with AHL acylases. PVAs are exploited widely in the pharmaceutical industry, but their role in the natural physiology of their native microbes is not clearly understood. This report details the characterization of AHL degradation activity by homotetrameric PVAs from two gram-negative plant pathogenic bacteria, Pectobacterium atrosepticum (PaPVA) and Agrobacterium tumefaciens (AtPVA). Both the PVAs exhibited substrate specificity for degrading long-chain AHLs. Exogenous addition of these enzymes into Pseudomonas aeruginosa greatly diminished the production of elastase and pyocyanin and biofilm formation and increased the survival rate in an insect model of acute infection. Subtle structural differences in the PVA active site that regulate specificity for acyl chain length have been characterized, which could reflect the evolution of AHL-degrading acylases in relation to the environment of the bacteria that produce them and also provide strategies for enzyme engineering. The potential for using these enzymes as therapeutic agents in clinical applications and a few ideas about their possible significance in microbial physiology have also been discussed.

  19. Determination of N-acylhomoserine lactones of Pseudomonas aeruginosa in clinical samples from dogs with otitis externa.

    PubMed

    Kušar, Darja; Šrimpf, Karin; Isaković, Petra; Kalšek, Lina; Hosseini, Javid; Zdovc, Irena; Kotnik, Tina; Vengušt, Modest; Tavčar-Kalcher, Gabrijela

    2016-10-18

    Bacterial intercellular communication, called quorum sensing, takes place via the production and collective response to signal molecules. In Gram-negative bacteria, like Pseudomonas aeruginosa, these signaling molecules are N-acylhomoserine lactones (AHLs). P. aeruginosa is a common cause of inflammation of the ear canal (otitis externa) in dogs. It employs quorum sensing to coordinate the expression of host tissue-damaging factors, which are largely responsible for its virulence. The treatment of P. aeruginosa-associated otitis is challenging due to a high intrinsic resistance of P. aeruginosa to several antibiotics. Attenuation of quorum sensing signals to inhibit bacterial virulence is a novel strategy for the treatment of resistant bacterial pathogens, including P. aeruginosa. Therefore, it is important to recognize and define quorum sensing signal molecules in clinical samples. To date, there are no reports on determination of AHLs in the veterinary clinical samples. The purpose of this study was to validate an analytical procedure for determination of the concentration of AHLs in the ear rinses from dogs with P. aeruginosa-associated otitis externa. Samples were obtained with rinsing the ear canals with physiological saline solution. For validation, samples from healthy dogs were spiked with none or different known amounts of the selected AHLs. With the validated procedure, AHLs were analyzed in the samples taken in weekly intervals from two dogs, receiving a standard treatment for P. aeruginosa-associated otitis externa. Validation proved that the procedure enables quantification of AHLs in non-clinical and clinical samples. In addition, a time dependent reduction of AHL concentration was detected for the treated dogs. Our results indicate that liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is superior in detecting AHLs compared to other chromatographic techniques. This is the first report on determination of AHLs in the clinical

  20. Long-chain acylhomoserine lactones increase the anoxic ammonium oxidation rate in an OLAND biofilm.

    PubMed

    De Clippeleir, Haydée; Defoirdt, Tom; Vanhaecke, Lynn; Vlaeminck, Siegfried E; Carballa, Marta; Verstraete, Willy; Boon, Nico

    2011-05-01

    The oxygen-limited autotrophic nitrification/denitrification (OLAND) process comprises one-stage partial nitritation and anammox, catalyzed by aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB), respectively. The goal of this study was to investigate whether quorum sensing influences anoxic ammonium oxidation in an OLAND biofilm, with AnAOB colonizing 13% of the biofilm, as determined with fluorescent in situ hybridization (FISH). At high biomass concentrations, the specific anoxic ammonium oxidation rate of the OLAND biofilm significantly increased with a factor of 1.5 ± 0.2 compared to low biomass concentrations. Supernatant obtained from the biofilm showed no ammonium-oxidizing activity on itself, but its addition to low OLAND biomass concentrations resulted in a significant activity increase of the biomass. In the biofilm supernatant, the presence of long-chain acylhomoserine lactones (AHLs) was shown using the reporter strain Chromobacterium violaceum CV026, and one specific AHL, N-dodecanoyl homoserine lactone (C(12)-HSL), was identified via LC-MS/MS. Furthermore, C(12)-HSL was detected in an AnAOB-enriched community, but not in an AerAOB-enriched community. Addition of C(12)-HSL to low OLAND biomass concentrations resulted in a significantly higher ammonium oxidation rate (p < 0.05). To our knowledge, this is the first report demonstrating that AHLs enhance the anoxic ammonium oxidation process. Future work should confirm which species are responsible for the in situ production of C(12)-HSL in AnAOB-based applications.

  1. A Comparative Analysis of Acyl-Homoserine Lactone Synthase Assays.

    PubMed

    Shin, Daniel; Frane, Nicole D; Brecht, Ryan M; Keeler, Jesse; Nagarajan, Rajesh

    2015-12-01

    Quorum sensing is cell-to-cell communication that allows bacteria to coordinate attacks on their hosts by inducing virulent gene expression, biofilm production, and other cellular functions, including antibiotic resistance. AHL synthase enzymes synthesize N-acyl-l-homoserine lactones, commonly referred to as autoinducers, to facilitate quorum sensing in Gram-negative bacteria. Studying the synthases, however, has proven to be a difficult road. Two assays, including a radiolabeled assay and a colorimetric (DCPIP) assay are well-documented in literature to study AHL synthases. In this paper, we describe additional methods that include an HPLC-based, C-S bond cleavage and coupled assays to investigate this class of enzymes. In addition, we compare and contrast each assay for both acyl-CoA- and acyl-ACP-utilizing synthases. The expanded toolkit described in this study should facilitate mechanistic studies on quorum sensing signal synthases and expedite discovery of antivirulent compounds.

  2. Acyl-homoserine lactone-based quorum sensing and quorum quenching hold promise to determine the performance of biological wastewater treatments: An overview.

    PubMed

    Huang, Jinhui; Shi, Yahui; Zeng, Guangming; Gu, Yanling; Chen, Guiqiu; Shi, Lixiu; Hu, Yi; Tang, Bi; Zhou, Jianxin

    2016-08-01

    Quorum sensing (QS) is a communication process between cells, in which bacteria secrete and sense the specific chemicals, and regulate gene expression in response to population density. Quorum quenching (QQ) blocks QS system, and inhibits gene expression mediating bacterial behaviors. Given the extensive research of acyl-homoserine lactone (AHL) signals, existences and effects of AHL-based QS and QQ in biological wastewater treatments are being subject to high concern. This review summarizes AHL structure, synthesis mode, degradation mechanisms, analytical methods, environmental factors, AHL-based QS and QQ mechanisms. The existences and roles of AHL-based QS and QQ in biomembrane processes, activated sludge processes and membrane bioreactors are summarized and discussed, and corresponding exogenous regulation strategy by selective enhancement of AHL-based QS or QQ coexisting in biological wastewater treatments is suggested. Such strategies including the addition of AHL signals, AHL-producing bacteria as well as quorum quenching enzyme or bacteria can effectively improve wastewater treatment performance without killing or limiting bacterial survival and growth. This review will present the theoretical and practical cognition for bacterial AHL-based QS and QQ, suggest the feasibility of exogenous regulation strategies in biological wastewater treatments, and provide useful information to scientists and engineers who work in this field. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Control of Acetic Acid Fermentation by Quorum Sensing via N-Acylhomoserine Lactones in Gluconacetobacter intermedius▿ †

    PubMed Central

    Iida, Aya; Ohnishi, Yasuo; Horinouchi, Sueharu

    2008-01-01

    A number of gram-negative bacteria regulate gene expression in a cell density-dependent manner by quorum sensing via N-acylhomoserine lactones (AHLs). Gluconacetobacter intermedius NCI1051, a gram-negative acetic acid bacterium, produces three different AHLs, N-decanoyl-l-homoserine lactone, N-dodecanoyl-l-homoserine lactone, and an N-dodecanoyl-l-homoserine lactone with a single unsaturated bond in its acyl chain, as determined by liquid chromatography-tandem mass spectrometry. Two genes encoding an AHL synthase and a cognate regulator were cloned from strain NCI1051 and designated ginI and ginR, respectively. Disruption of ginI or ginR abolished AHL production, indicating that NCI1051 contains a single set of quorum-sensing genes. Transcriptional analysis showed that ginI is activated by GinR, which is consistent with the finding that there is an inverted repeat whose nucleotide sequence is similar to the sequence bound by members of the LuxR family at position −45 with respect to the transcriptional start site of ginI. A single gene, designated ginA, located just downstream of ginI is transcribed by read-through from the GinR-inducible ginI promoter. A ginA mutant, as well as the ginI and ginR mutants, grew more rapidly in medium containing 2% (vol/vol) ethanol and accumulated acetic acid at a higher rate with a greater final yield than parental strain NCI1051. In addition, these mutants produced larger amounts of gluconic acid than the parental strain. These data demonstrate that the GinI/GinR quorum-sensing system in G. intermedius controls the expression of ginA, which in turn represses oxidative fermentation, including acetic acid and gluconic acid fermentation. PMID:18245283

  4. Comprehensive profiling of N-acylhomoserine lactones produced by Yersinia pseudotuberculosis using liquid chromatography coupled to hybrid quadrupole-linear ion trap mass spectrometry.

    PubMed

    Ortori, Catharine A; Atkinson, Steve; Chhabra, Siri Ram; Cámara, Miguel; Williams, Paul; Barrett, David A

    2007-01-01

    A method for the comprehensive profiling of the N-acylhomoserine lactone (AHL) family of bacterial quorum-sensing molecules is presented using liquid chromatography (LC) coupled to hybrid quadrupole-linear ion trap (QqQLIT) mass spectrometry. Information-dependent acquisition (IDA), using triggered combinations of triple-quadrupole and linear ion trap modes in the same LC-MS/MS run, was used to simultaneously screen, quantify and identify multiple AHLs in a single sample. This MS method uses common AHL fragment ions attributed to the homoserine moiety and the 3-oxo-, 3-hydroxy- or unsubstituted acyl side chains, to identify unknown AHLs in cell-free culture supernatants in an unbiased manner. This LC-MS technique was applied to determine the relative molar ratios of AHLs produced by Yersinia pseudotuberculosis and the consequences of inactivating by mutation either or both of the AHL synthase genes (ypsI and ytbI) on AHL profile and concentration. The Y. pseudotuberculosis wild type but not the ypsI ytbI double mutant produced at least 24 different AHLs with acyl chains ranging from C4 to C15 with or without 3-oxo or 3-hydroxy substituents. YtbI, in contrast to YpsI, could direct the synthesis of all of the AHLs identified. The most abundant and hence most biologically relevant Y. pseudotuberculosis AHLs were found to be the 3-oxo-substituted C6, C7 and C8 AHLs and the unsubstituted C6 and C8 compounds. The LC-QqQLIT methodology is broadly applicable to quorum-sensing signal molecule analysis and can provide comprehensive AHL profiles and concentrations from a single sample and simultaneously collect confirmatory spectra for each AHL identified.

  5. Acyl-homoserine lactone quorum sensing: from evolution to application.

    PubMed

    Schuster, Martin; Sexton, D Joseph; Diggle, Stephen P; Greenberg, E Peter

    2013-01-01

    Quorum sensing (QS) is a widespread process in bacteria that employs autoinducing chemical signals to coordinate diverse, often cooperative activities such as bioluminescence, biofilm formation, and exoenzyme secretion. Signaling via acyl-homoserine lactones is the paradigm for QS in Proteobacteria and is particularly well understood in the opportunistic pathogen Pseudomonas aeruginosa. Despite thirty years of mechanistic research, empirical studies have only recently addressed the benefits of QS and provided support for the traditional assumptions regarding its social nature and its role in optimizing cell-density-dependent group behaviors. QS-controlled public-goods production has served to investigate principles that explain the evolution and stability of cooperation, including kin selection, pleiotropic constraints, and metabolic prudence. With respect to medical application, appreciating social dynamics is pertinent to understanding the efficacy of QS-inhibiting drugs and the evolution of resistance. Future work will provide additional insight into the foundational assumptions of QS and relate laboratory discoveries to natural ecosystems.

  6. Acyl-Homoserine Lactone Quorum Sensing in the Roseobacter Clade

    PubMed Central

    Zan, Jindong; Liu, Yue; Fuqua, Clay; Hill, Russell T.

    2014-01-01

    Members of the Roseobacter clade are ecologically important and numerically abundant in coastal environments and can associate with marine invertebrates and nutrient-rich marine snow or organic particles, on which quorum sensing (QS) may play an important role. In this review, we summarize current research progress on roseobacterial acyl-homoserine lactone-based QS, particularly focusing on three relatively well-studied representatives, Phaeobacter inhibens DSM17395, the marine sponge symbiont Ruegeria sp. KLH11 and the dinoflagellate symbiont Dinoroseobacter shibae. Bioinformatic survey of luxI homologues revealed that over 80% of available roseobacterial genomes encode at least one luxI homologue, reflecting the significance of QS controlled regulatory pathways in adapting to the relevant marine environments. We also discuss several areas that warrant further investigation, including studies on the ecological role of these diverse QS pathways in natural environments. PMID:24402124

  7. N-Acylhomoserine Lactones Undergo Lactonolysis in a pH-, Temperature-, and Acyl Chain Length-Dependent Manner during Growth of Yersinia pseudotuberculosis and Pseudomonas aeruginosa

    PubMed Central

    Yates, Edwin A.; Philipp, Bodo; Buckley, Catherine; Atkinson, Steve; Chhabra, Siri Ram; Sockett, R. Elizabeth; Goldner, Morris; Dessaux, Yves; Cámara, Miguel; Smith, Harry; Williams, Paul

    2002-01-01

    In gram-negative bacterial pathogens, such as Pseudomonas aeruginosa and Yersinia pseudotuberculosis, cell-to-cell communication via the N-acylhomoserine lactone (AHL) signal molecules is involved in the cell population density-dependent control of genes associated with virulence. This phenomenon, termed quorum sensing, relies upon the accumulation of AHLs to a threshold concentration at which target structural genes are activated. By using biosensors capable of detecting a range of AHLs we observed that, in cultures of Y. pseudotuberculosis and P. aeruginosa, AHLs accumulate during the exponential phase but largely disappear during the stationary phase. When added to late-stationary-phase, cell-free culture supernatants of the respective pathogen, the major P. aeruginosa [N-butanoylhomoserine lactone (C4-HSL) and N-(3-oxododecanoyl)homoserine lactone (3-oxo-C12-HSL)] and Y. pseudotuberculosis [N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL)] AHLs were inactivated. Short-acyl-chain compounds (e.g., C4-HSL) were turned over more extensively than long-chain molecules (e.g., 3-oxo-C12-HSL). Little AHL inactivation occurred with cell extracts, and no evidence for inactivation by specific enzymes was apparent. This AHL turnover was discovered to be due to pH-dependent lactonolysis. By acidifying the growth media to pH 2.0, lactonolysis could be reversed. By using carbon-13 nuclear magnetic resonance spectroscopy, we found that the ring opening of homoserine lactone (HSL), N-propionyl HSL (C3-HSL), and C4-HSL increased as pH increased but diminished as the N-acyl chain was lengthened. At low pH levels, the lactone rings closed but not via a simple reversal of the ring opening reaction mechanism. Ring opening of C4-HSL, C6-HSL, 3-oxo-C6-HSL, and N-octanoylhomoserine lactone (C8-HSL), as determined by the reduction of pH in aqueous solutions with time, was also less rapid for AHLs with more electron-donating longer side chains

  8. N-acylhomoserine lactones undergo lactonolysis in a pH-, temperature-, and acyl chain length-dependent manner during growth of Yersinia pseudotuberculosis and Pseudomonas aeruginosa.

    PubMed

    Yates, Edwin A; Philipp, Bodo; Buckley, Catherine; Atkinson, Steve; Chhabra, Siri Ram; Sockett, R Elizabeth; Goldner, Morris; Dessaux, Yves; Cámara, Miguel; Smith, Harry; Williams, Paul

    2002-10-01

    In gram-negative bacterial pathogens, such as Pseudomonas aeruginosa and Yersinia pseudotuberculosis, cell-to-cell communication via the N-acylhomoserine lactone (AHL) signal molecules is involved in the cell population density-dependent control of genes associated with virulence. This phenomenon, termed quorum sensing, relies upon the accumulation of AHLs to a threshold concentration at which target structural genes are activated. By using biosensors capable of detecting a range of AHLs we observed that, in cultures of Y. pseudotuberculosis and P. aeruginosa, AHLs accumulate during the exponential phase but largely disappear during the stationary phase. When added to late-stationary-phase, cell-free culture supernatants of the respective pathogen, the major P. aeruginosa [N-butanoylhomoserine lactone (C4-HSL) and N-(3-oxododecanoyl)homoserine lactone (3-oxo-C12-HSL)] and Y. pseudotuberculosis [N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL)] AHLs were inactivated. Short-acyl-chain compounds (e.g., C4-HSL) were turned over more extensively than long-chain molecules (e.g., 3-oxo-C12-HSL). Little AHL inactivation occurred with cell extracts, and no evidence for inactivation by specific enzymes was apparent. This AHL turnover was discovered to be due to pH-dependent lactonolysis. By acidifying the growth media to pH 2.0, lactonolysis could be reversed. By using carbon-13 nuclear magnetic resonance spectroscopy, we found that the ring opening of homoserine lactone (HSL), N-propionyl HSL (C3-HSL), and C4-HSL increased as pH increased but diminished as the N-acyl chain was lengthened. At low pH levels, the lactone rings closed but not via a simple reversal of the ring opening reaction mechanism. Ring opening of C4-HSL, C6-HSL, 3-oxo-C6-HSL, and N-octanoylhomoserine lactone (C8-HSL), as determined by the reduction of pH in aqueous solutions with time, was also less rapid for AHLs with more electron-donating longer side chains

  9. Quorum sensing by N-acylhomoserine lactones is not required for Aeromonas hydrophila during growth with organic particles in lake water microcosms.

    PubMed

    Styp von Rekowski, Katharina; Hempel, Melanie; Philipp, Bodo

    2008-05-01

    It was investigated whether quorum sensing (QS) mediated by N-acylhomoserine lactones (AHLs) was important for heterotrophic bacteria from the littoral zone of the oligotrophic Lake Constance for growth with organic particles. More than 900 colonies from lake water microcosms with artificial organic aggregates consisting of autoclaved unicellular algae embedded in agarose beads were screened for AHL-production. AHL-producing bacteria of the genus Aeromonas enriched in the microcosms but AHLs could not be detected in any microcosm. To test for a potential function of AHL-mediated QS, growth experiments with the wild type and an AHL-deficient mutant of Aeromonas hydrophila in lake water microcosms were performed. Growth of both strains did not differ in single cultures and showed no mutual influence in co-cultures. In co-cultures with a competitor bacterium belonging to the Cytophaga-Flavobacterium group, growth of both A. hydrophila strains was reduced while growth of the competitor bacterium was not affected. Exogenous AHL-addition did not influence growth of the Aeromonas strains in any microcosm experiment. These results showed that AHL-mediated QS was not required for A. hydrophila during colonization and degradation of organic particles in lake water microcosms, suggesting that cell-cell signalling of heterotrophic bacteria in oligotrophic waters relies on novel signal molecules.

  10. Presence of Acylated Homoserine Lactones (AHLs) and AHL-Producing Bacteria in Meat and Potential Role of AHL in Spoilage of Meat

    PubMed Central

    Bruhn, Jesper Bartholin; Christensen, Allan Beck; Flodgaard, Lars Ravn; Nielsen, Kristian Fog; Larsen, Thomas Ostenfeld; Givskov, Michael; Gram, Lone

    2004-01-01

    Quorum-sensing (QS) signals (N-acyl homoserine lactones [AHLs]) were extracted and detected from five commercially produced vacuum-packed meat samples. Ninety-six AHL-producing bacteria were isolated, and 92 were identified as Enterobacteriaceae. Hafnia alvei was the most commonly identified AHL-producing bacterium. Thin-layer chromatographic profiles of supernatants from six H. alvei isolates and of extracts from spoiling meat revealed that the major AHL species had an Rf value and shape similar to N-3-oxo-hexanoyl homoserine lactone (OHHL). Liquid chromatography-mass spectrometry (MS) (high-resolution MS) analysis confirmed the presence of OHHL in pure cultures of H. alvei. Vacuum-packed meat spoiled at the same rate when inoculated with the H. alvei wild type compared to a corresponding AHL-lacking mutant. Addition of specific QS inhibitors to the AHL-producing H. alvei inoculated in meat or to naturally contaminated meat did not influence the spoilage of vacuum-packed meat. An extracellular protein of approximately 20 kDa produced by the H. alvei wild-type was not produced by the AHL-negative mutant but was restored in the mutant when complemented by OHHL, thus indicating that AHLs do have a regulatory role in H. alvei. Coinoculation of H. alvei wild-type with an AHL-deficient Serratia proteamaculans B5a, in which protease secretion is QS regulated, caused spoilage of liquid milk. By contrast, coinoculation of AHL-negative strains of H. alvei and S. proteamaculans B5a did not cause spoilage. In conclusion, AHL and AHL-producing bacteria are present in vacuum-packed meat during storage and spoilage, but AHL does not appear to influence the spoilage of this particular type of conserved meat. Our data indicate that AHL-producing H. alvei may induce food quality-relevant phenotypes in other bacterial species in the same environment. H. alvei may thus influence spoilage of food products in which Enterobacteriaceae participate in the spoilage process. PMID:15240313

  11. N-acylhomoserine lactone-regulation of genes mediating motility and pathogenicity in Pseudomonas syringae pathovar tabaci 11528.

    PubMed

    Cheng, Feifei; Ma, Anzhou; Luo, Jinxue; Zhuang, Xuliang; Zhuang, Guoqiang

    2017-01-29

    Pseudomonas syringae pathovar tabaci 11528 (P. syringae 11528) is a phytopathogen that causes wild-fire disease in soybean and tobacco plants. It utilizes a cell density-dependent regulation system known as quorum sensing (QS). In its QS system, the psyI is responsible for the biosynthesis of N-acylhomoserine lactones (AHLs). By comparing the transcripts from P. syringae 11528 wild-type strain with those of the ΔpsyI mutant using RNA sequencing (RNA-seq) technology, 1118 AHL-regulated genes were identified in the transition from exponential to stationary growth phase. Numerous AHL-regulated genes involved in pathogenicity were negatively controlled, including genes linked to flagella, chemotaxis, pilus, extracellular polysaccharides, secretion systems, and two-component system. Moreover, gene ontology and pathway enrichment analysis revealed that the most pronounced regulation was associated with bacterial motility. Finally, phenotypic assays showed that QS-regulated traits were involved in epiphytic growth of pathogens and disease development in plants. These findings imply that the AHL-mediated QS system in P. syringae 11528 plays significant roles in distinct stages of interactions between plants and pathogens, including early plant colonization and late plant infection.

  12. Acyl-homoserine lactone-dependent eavesdropping promotes competition in a laboratory co-culture model

    PubMed Central

    Chandler, Josephine R; Heilmann, Silja; Mittler, John E; Greenberg, E Peter

    2012-01-01

    Many Proteobacteria use acyl-homoserine lactone (AHL)-mediated quorum sensing to activate the production of antibiotics at high cell density. Extracellular factors like antibiotics can be considered public goods shared by individuals within a group. Quorum-sensing control of antibiotic production may be important for protecting a niche or competing for limited resources in mixed bacterial communities. To begin to investigate the role of quorum sensing in interspecies competition, we developed a dual-species co-culture model using the soil saprophytes Burkholderia thailandensis (Bt) and Chromobacterium violaceum (Cv). These bacteria require quorum sensing to activate the production of antimicrobial factors that inhibit growth of the other species. We demonstrate that quorum-sensing-dependent antimicrobials can provide a competitive advantage to either Bt or Cv by inhibiting growth of the other species in co-culture. Although the quorum-sensing signals differ for each species, we show that the promiscuous signal receptor encoded by Cv can sense signals produced by Bt, and that this ability to eavesdrop on Bt can provide Cv an advantage in certain situations. We use an in silico approach to investigate the effect of eavesdropping in competition, and show conditions where early activation of antibiotic production resulting from eavesdropping can promote competitiveness. Our work supports the idea that quorum sensing is important for interspecies competition and that promiscuous signal receptors allow eavesdropping on competitors in mixed microbial habitats. PMID:22763647

  13. The acyl-homoserine lactone-type quorum-sensing system modulates cell motility and virulence of Erwinia chrysanthemi pv. zeae.

    PubMed

    Hussain, Mumtaz B B M; Zhang, Hai-Bao; Xu, Jin-Ling; Liu, Qiongguang; Jiang, Zide; Zhang, Lian-Hui

    2008-02-01

    Erwinia chrysanthemi pv. zeae is one of the Erwinia chrysanthemi pathovars that infects on both dicotyledons and monocotyledons. However, little is known about the molecular basis and regulatory mechanisms of its virulence. By using a transposon mutagenesis approach, we cloned the genes coding for an E. chrysanthemi pv. zeae synthase of acyl-homoserine lactone (AHL) quorum-sensing signals (expI(Ecz)) and a cognate response regulator (expR(Ecz)). Chromatography analysis showed that expI(Ecz) encoded production of the AHL signal N-(3-oxo-hexanoyl)-homoserine lactone (OHHL). Null mutation of expI(Ecz) in the E. chrysanthemi pv. zeae strain EC1 abolished AHL production, increased bacterial swimming and swarming motility, disabled formation of multicell aggregates, and attenuated virulence of the pathogen on potato tubers. The mutation also marginally reduced the inhibitory activity of E. chrysanthemi pv. zeae on rice seed germination. The mutant phenotypes were rescued by either exogenous addition of AHL signal or in trans expression of expI(Ecz). These data demonstrate that the AHL-type QS signal plays an essential role in modulation of E. chrysanthemi pv. zeae cell motility and the ability to form multicell aggregates and is involved in regulation of bacterial virulence.

  14. A solo luxI-type gene directs acylhomoserine lactone synthesis and contributes to motility control in the marine sponge symbiont Ruegeria sp. KLH11

    PubMed Central

    Zan, Jindong; Choi, Okhee; Meharena, Hiruy; Uhlson, Charis L.; Churchill, Mair E. A.; Hill, Russell T.

    2015-01-01

    Marine sponges harbour abundant and diverse bacterial communities, providing an ideal environment for bacterial cell-density-dependent cell–cell signalling, termed quorum sensing. The marine sponge symbiont Ruegeria sp. KLH11 produces mainly long chain acylhomoserine lactones (AHLs) and has been developed as a quorum sensing model for roseobacterial sponge symbionts. Two pairs of luxR/I homologues were identified by genetic screening and were designated ssaRI and ssbRI (sponge-associated symbiont locus A or B, luxR/luxI homologue). In this study, we identified a third luxI-type gene, named sscI. The sscI gene does not have a cognate luxR homologue present at an adjacent locus and thus sscI is an AHL synthase solo. The sscI gene is required for production of long-chain hydroxylated AHLs, contributes to AHL pools and modestly influences flagellar motility in KLH11. A triple mutant for all luxI-type genes cannot produce AHLs, but still synthesizes para-coumaroyl-homoserine lactone. PMID:25355937

  15. A solo luxI-type gene directs acylhomoserine lactone synthesis and contributes to motility control in the marine sponge symbiont Ruegeria sp. KLH11.

    PubMed

    Zan, Jindong; Choi, Okhee; Meharena, Hiruy; Uhlson, Charis L; Churchill, Mair E A; Hill, Russell T; Fuqua, Clay

    2015-01-01

    Marine sponges harbour abundant and diverse bacterial communities, providing an ideal environment for bacterial cell-density-dependent cell-cell signalling, termed quorum sensing. The marine sponge symbiont Ruegeria sp. KLH11 produces mainly long chain acylhomoserine lactones (AHLs) and has been developed as a quorum sensing model for roseobacterial sponge symbionts. Two pairs of luxR/I homologues were identified by genetic screening and were designated ssaRI and ssbRI (sponge-associated symbiont locus A or B, luxR/luxI homologue). In this study, we identified a third luxI-type gene, named sscI. The sscI gene does not have a cognate luxR homologue present at an adjacent locus and thus sscI is an AHL synthase solo. The sscI gene is required for production of long-chain hydroxylated AHLs, contributes to AHL pools and modestly influences flagellar motility in KLH11. A triple mutant for all luxI-type genes cannot produce AHLs, but still synthesizes para-coumaroyl-homoserine lactone. © 2015 The Authors.

  16. Microbial homoserine lactones (AHLs) are effectors of root morphological changes in barley.

    PubMed

    Rankl, Simone; Gunsé, Benet; Sieper, Tina; Schmid, Christoph; Poschenrieder, Charlotte; Schröder, Peter

    2016-12-01

    While colonizing the rhizosphere, bacterial intra- and inter-specific communication is accomplished by N-Acyl-homoserine-lactones (AHLs) in a density-dependent manner. Moreover, plants are naturally exposed to AHLs and respond with tissue-specificity. In the present study, we investigated the influence of N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL) and N-dodecanoyl-d/l-homoserine lactone (C12-HSL) on growth and root development in barley (Hordeum vulgare L.), and identified initial reactions in root cells after AHL exposures using physiological, staining, and electrophysiological methods. Treatment with short- and long-chain AHLs modulated plant growth and branched root architecture and induced nitric oxide (NO) accumulation in the calyptra and root elongation zone of excised roots in an AHL derivative-independent way. Additionally, C6- and C8-HSL treatments stimulated K(+) uptake in root cells only at certain concentrations, whereas all tested concentrations of C12-HSL induced K(+) uptake. In further experiments, C8-HSL promoted membrane hyperpolarization in epidermal root cells. Thus, we conclude AHLs promote plant growth and lateral root formation, and cause NO accumulation as an early response to AHLs. Furthermore, the AHL-mediated membrane hyperpolarization is leading to increased K(+) uptake of the root tissue. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  17. Synthesis of “clickable” acylhomoserine lactone quorum sensing probes: unanticipated effects on mammalian cell activation

    PubMed Central

    Garner, Amanda L.; Yu, Jing; Struss, Anjali Kumari; Lowery, Colin A.; Zhu, Jie; Kim, Sook Kyung; Park, Junguk; Mayorov, Alexander V.; Kaufmann, Gunnar F.; Kravchenko, Vladimir V.; Janda, Kim D.

    2010-01-01

    Alkynyl- and azido-tagged 3-oxo-C12-acylhomoserine lactone probes have been synthesized to examine their potential utility as probes for discovering the mammalian protein target of the Pseudomonas aeruginosa autoinducer, 3-oxo-C12-acylhomoserine lactone. Although such substitutions are commonly believed to be quite conservative, from these studies, we have uncovered a drastic difference in activity between the alkynyl- and azido-modified compounds, and provide an example where such structural modification has proved to be much less than conservative. PMID:21190852

  18. The Acyl-Homoserine Lactone Synthase YenI from Yersinia enterocolitica Modulates Virulence Gene Expression in Enterohemorrhagic Escherichia coli O157:H7

    PubMed Central

    Nguyen, Y N.; Sheng, Haiqing; Dakarapu, Rambabu; Falck, John R.; Hovde, Carolyn J.

    2013-01-01

    The human pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 colonizes the rectoanal junction (RAJ) in cattle, its natural reservoir. Colonization at the RAJ poses a serious risk for fecal shedding and contamination of the environment. We previously demonstrated that EHEC senses acyl-homoserine lactones (AHLs) produced by the microbiota in the rumen to activate the gad acid resistance genes necessary for survival through the acidic stomachs in cattle and to repress the locus of enterocyte effacement (LEE) genes important for colonization of the RAJ, but unnecessary in the rumen. Devoid of AHLs, the RAJ is the prominent site of colonization of EHEC in cattle. To determine if the presence of AHLs in the RAJ could repress colonization at this site, we engineered EHEC to express the Yersinia enterocolitica AHL synthase gene yenI, which constitutively produces AHLs, to mimic a constant exposure of AHLs in the environment. The yenI+ EHEC produces oxo-C6-homoserine lactone (oxo-C6-HSL) and had a significant reduction in LEE expression, effector protein secretion, and attaching and effacing (A/E) lesion formation in vitro compared to the wild type (WT). The yenI+ EHEC also activated expression of the gad genes. To assess whether AHL production, which decreases LEE expression, would decrease RAJ colonization by EHEC, cattle were challenged at the RAJ with WT or yenI+ EHEC. Although the yenI+ EHEC colonized the RAJ with efficiency equal to that of the WT, there was a trend for the cattle to shed the WT strain longer than the yenI+ EHEC. PMID:23980115

  19. N-acylated alanine methyl esters (NAMEs) from Roseovarius tolerans, structural analogs of quorum-sensing autoinducers, N-acylhomoserine lactones.

    PubMed

    Bruns, Hilke; Thiel, Verena; Voget, Sonja; Patzelt, Diana; Daniel, Rolf; Wagner-Döbler, Irene; Schulz, Stefan

    2013-09-01

    The Roseobacter clade is one of the most important bacteria group living in the ocean. Liquid cultures of Roseovarius tolerans EL 164 were investigated for the production of autoinducers such as N-acylhomoserine lactones (AHLs) and other secondary metabolites. The XAD extracts were analyzed by GC/MS. Two AHLs, Z7-C14 : 1-homoserine lactone (HSL) and C15 : 1-HSL, were identified. Additionally, the extract contained five compounds with molecular-ion peaks at m/z 104, 145, and 158, thus exhibiting mass spectra similar to those of AHLs with corresponding peaks at m/z 102, 143, and 156. Isolation of the main compound by column chromatography, NMR analysis, dimethyl disulfide derivatization for the determination of the location of the CC bond and finally synthesis of the compound with the proposed structure confirmed the compound to be (Z)-N-(hexadec-9-enoyl)alanine methyl ester. Four additional minor compounds were identified as C14 : 0-, C15 : 0-, C16 : 0-, and C17 : 1-N-acylated alanine methyl esters (NAMEs). All NAMEs have not been described from natural sources before. A BLASTp search showed the presence of AHL-producing luxI genes, but no homologous genes potentially responsible for the structurally closely related NAMEs were found. The involvement of the NAMEs in chemical communication processes of the bacteria is discussed.

  20. Regulation of acylated homoserine lactones (AHLs) in beef by spice marination.

    PubMed

    Gopu, Venkadesaperumal; Shetty, Prathapkumar Halady

    2016-06-01

    Quorum sensing (QS) is a signaling mechanism used by bacteria to communicate each other through the release of auto-inducing signaling molecules. Despite the fact that bacteria regulate its phenotypes by QS mechanism, their potential role in meat spoilage is not yet elucidated. In the current study, beef samples were analyzed for its microbial association and for the presence of N-acyl-homoserine-lactone (AHLs) throughout the storage experiments. Isolates were screened for AHLs production and selected spices were screened for their quorum sensing inhibitory (QSI) activity. In addition, effect of spices on AHLs production of Y. enterocolitica was quantified through high performance thin layer chromatography (HP-TLC). Outcome showed that microbial association of beef mainly consists of lactic acid bacteria (LAB) and Enterobacteriaceae. Samples stored at both aerobic and modified atmospheric packaging (MAP) exhibited higher counts whereas; marinated samples stored at MAP exhibited the lowest. It was found that out of 35 isolates Y. enterocolitica induced reporter strain CV026 and its cell-free supernatant contained 26.36 nM/100 ml of AHLs when compared to standard. Among the tested spices, C. cyminum exhibited pronounced results by significantly reducing the AHLs concentration up to 47.75 %. Findings revealed the presence of quorum molecules (AHLs) in beef meat throughout the spoilage process and spices can acts as quorum quenchers to influence the spoilage rate by reducing AHLs production.

  1. The Pseudomonas aeruginosa N-Acylhomoserine Lactone Quorum Sensing Molecules Target IQGAP1 and Modulate Epithelial Cell Migration

    PubMed Central

    Karlsson, Thommie; Turkina, Maria V.; Yakymenko, Olena; Magnusson, Karl-Eric; Vikström, Elena

    2012-01-01

    Quorum sensing (QS) signaling allows bacteria to control gene expression once a critical population density is achieved. The Gram-negative human pathogen Pseudomonas aeruginosa uses N-acylhomoserine lactones (AHL) as QS signals, which coordinate the production of virulence factors and biofilms. These bacterial signals can also modulate human cell behavior. Little is known about the mechanisms of the action of AHL on their eukaryotic targets. Here, we found that N-3-oxo-dodecanoyl-L-homoserine lactone 3O-C12-HSL modulates human intestinal epithelial Caco-2 cell migration in a dose- and time-dependent manner. Using new 3O-C12-HSL biotin and fluorescently-tagged probes for LC-MS/MS and confocal imaging, respectively, we demonstrated for the first time that 3O-C12-HSL interacts and co-localizes with the IQ-motif-containing GTPase-activating protein IQGAP1 in Caco-2 cells. The interaction between IQGAP1 and 3O-C12-HSL was further confirmed by pull-down assay using a GST-tagged protein with subsequent Western blot of IQGAP1 and by identifying 3O-C12-HSL with a sensor bioassay. Moreover, 3O-C12-HSL induced changes in the phosphorylation status of Rac1 and Cdc42 and the localization of IQGAP1 as evidenced by confocal and STED microscopy and Western blots. Our findings suggest that the IQGAP1 is a novel partner for P.aeruginosa 3O-C12-HSL and likely the integrator of Rac1 and Cdc42- dependent altered cell migration. We propose that the targeting of IQGAP1 by 3O-C12-HSL can trigger essential changes in the cytoskeleton network and be an essential component in bacterial – human cell communication. PMID:23071436

  2. In situ quantitation of the spatial scale of calling distances and population density-independent N-acylhomoserine lactone-mediated communication by rhizobacteria colonized on plant roots.

    PubMed

    Gantner, Stephan; Schmid, Michael; Dürr, Christine; Schuhegger, Regina; Steidle, Anette; Hutzler, Peter; Langebartels, Christian; Eberl, Leo; Hartmann, Anton; Dazzo, Frank B

    2006-05-01

    We used computer-assisted microscopy at single cell resolution to quantify the in situ spatial scale of N-acylhomoserine lactone (AHL)-mediated cell-to-cell communication of Pseudomonas putida colonized on tomato and wheat root surfaces. The results of this in situ quantification study on close-to-natural surfaces challenge the conventional view of a quorum group requirement of high cell densities for this type of bacterial communication. In situ image analysis indicated that the effective 'calling distance' on root surfaces was most frequent at 4-5 microm, extended to 37 microm in the root tip/elongation zone and further out to 78 microm in the root hair zone. The spatial scale of these calling distances is very long-range in proportion to the size of individual bacteria. Geostatistical modeling analysis implicated the importance of AHL-gradients mediating effective communication between remote cells. We conclude that AHL-mediated cell-to-cell communication occurs not only within dense populations, but also in very small groups and over long ranges between individual bacteria, and therefore this cellular activity is more commonplace and effective than hitherto predicted. We propose that this cell-to-cell communication is governed more by the in situ spatial proximity of cells within AHL-gradients than the requirement for a quorum group of high population density.

  3. Modulation of violacein production and phenotypes associated with biofilm by exogenous quorum sensing N-acylhomoserine lactones in the marine bacterium Pseudoalteromonas ulvae TC14.

    PubMed

    Mireille Ayé, Armande; Bonnin-Jusserand, Maryse; Brian-Jaisson, Florence; Ortalo-Magné, Annick; Culioli, Gérald; Koffi Nevry, Rose; Rabah, Nadia; Blache, Yves; Molmeret, Maëlle

    2015-10-01

    Various phenotypes ranging from biofilm formation to pigment production have been shown to be regulated by quorum sensing (QS) in many bacteria. However, studies of the regulation of pigments produced by marine bacteria in saline conditions and of biofilm-associated phenotypes are scarcer. This study focuses on the demonstration of the existence of a QS communication system involving N-acylhomoserine lactones (AHLs) in the Mediterranean Sea strain Pseudoalteromonas ulvae TC14. We have investigated whether TC14 produces the violacein pigment, and whether intrinsic or exogenous AHLs could influence its production and modulate biofilm-associated phenotypes. Here, we demonstrate that the purple pigment produced by TC14 is violacein. The study shows that in planktonic conditions, TC14 produces more pigment in the medium in which it grows less. Using different approaches, the results also show that TC14 does not produce intrinsic AHLs in our conditions. When exogenous AHLs are added in planktonic conditions, the production of violacein is upregulated by C6-, C12-, 3-oxo-C8 and 3-oxo-C12-HSLs (homoserine lactones), and downregulated by 3-oxo-C6-HSL. In sessile conditions, 3-oxo-C8-HSL upregulates the production of violacein. The study of the biofilm-associated phenotypes shows that oxo-derived-HSLs decrease adhesion, swimming and biofilm formation. While 3-oxo-C8 and 3-oxo-C12-HSLs decrease both swimming and adhesion, 3-oxo-C6-HSLs decrease not only violacein production in planktonic conditions but also swimming, adhesion and more subtly biofilm formation. Therefore, TC14 may possess a functional LuxR-type QS receptor capable of sensing extrinsic AHLs, which controls violacein production, motility, adhesion and biofilm formation.

  4. Transcriptome analysis of acyl-homoserine lactone-based quorum sensing regulation in Yersinia pestis [corrected].

    PubMed

    LaRock, Christopher N; Yu, Jing; Horswill, Alexander R; Parsek, Matthew R; Minion, F Chris

    2013-01-01

    The etiologic agent of bubonic plague, Yersinia pestis, senses self-produced, secreted chemical signals in a process named quorum sensing. Though the closely related enteric pathogen Y. pseudotuberculosis uses quorum sensing system to regulate motility, the role of quorum sensing in Y. pestis has been unclear. In this study we performed transcriptional profiling experiments to identify Y. pestis quorum sensing regulated functions. Our analysis revealed that acyl-homoserine lactone-based quorum sensing controls the expression of several metabolic functions. Maltose fermentation and the glyoxylate bypass are induced by acyl-homoserine lactone signaling. This effect was observed at 30°C, indicating a potential role for quorum sensing regulation of metabolism at temperatures below the normal mammalian temperature. It is proposed that utilization of alternative carbon sources may enhance growth and/or survival during prolonged periods in natural habitats with limited nutrient sources, contributing to maintenance of plague in nature.

  5. Positive Autoregulation of an Acyl-Homoserine Lactone Quorum-Sensing Circuit Synchronizes the Population Response.

    PubMed

    Scholz, Rebecca L; Greenberg, E Peter

    2017-07-25

    Many proteobacteria utilize acyl-homoserine lactone quorum-sensing signals. At low population densities, cells produce a basal level of signal, and when sufficient signal has accumulated in the surrounding environment, it binds to its receptor, and quorum-sensing-dependent genes can be activated. A common characteristic of acyl-homoserine lactone quorum sensing is that signal production is positively autoregulated. We have examined the role of positive signal autoregulation in Pseudomonas aeruginosa We compared population responses and individual cell responses in populations of wild-type P. aeruginosa to responses in a strain with the signal synthase gene controlled by an arabinose-inducible promoter so that signal was produced at a constant rate per cell regardless of cell population density. At a population level, responses of the wild type and the engineered strain were indistinguishable, but the responses of individual cells in a population of the wild type showed greater synchrony than the responses of the engineered strain. Although sufficient signal is required to activate expression of quorum-sensing-regulated genes, it is not sufficient for activation of certain genes, the late genes, and their expression is delayed until other conditions are met. We found that late gene responses were reduced in the engineered strain. We conclude that positive signal autoregulation is not a required element in acyl-homoserine lactone quorum sensing, but it functions to enhance synchrony of the responses of individuals in a population. Synchrony might be advantageous in some situations, whereas a less coordinated quorum-sensing response might allow bet hedging and be advantageous in other situations.IMPORTANCE There are many quorum-sensing systems that involve a transcriptional activator, which responds to an acyl-homoserine lactone signal. In all of the examples studied, the gene coding for signal production is positively autoregulated by the signal, and it has even

  6. Evidence for the dynamics of Acyl homoserine lactone and AHL-producing bacteria during subtidal biofilm formation.

    PubMed

    Huang, Yi-Li; Ki, Jang-Seu; Lee, On On; Qian, Pei-Yuan

    2009-03-01

    The quorum sensing signals-acyl homoserine lactones (AHLs) were directly detected in 1-9-day-old subtidal biofilms developed in a coastal fish farm by using AHL reporter strains and gas chromatography-mass spectrometry. Both methods showed that the AHL molecules and/or AHL-producing bacterial community were dynamic during biofilm development, with dominant AHLs changed from short-chain to long-chain AHLs. Terminal restriction fragment length polymorphism analysis of the bacterial 16S rRNA genes derived from subtidal biofilms of different ages was compared to that of the 21 AHL-producing bacteria isolated from the same batch of subtidal biofilms. All terminal restriction fragments (TRFs) generated from AHL-producing bacteria matched with the dominant TRFs derived from the biofilm bacterial community samples. Particularly, the TRFs of all AHL-producing Vibrio spp. matched with the TRFs that were dominant only in 1-day-old biofilm, suggesting that AHL-producing vibrios were one of the pioneer groups during subtidal biofilm formation. We reported here for the first time the dynamics of AHLs and AHL-producing bacteria during the formation of a subtidal biofilm.

  7. Selection of the N-Acylhomoserine Lactone-Degrading Bacterium Alteromonas stellipolaris PQQ-42 and of Its Potential for Biocontrol in Aquaculture

    PubMed Central

    Torres, Marta; Rubio-Portillo, Esther; Antón, Josefa; Ramos-Esplá, Alfonso A.; Quesada, Emilia; Llamas, Inmaculada

    2016-01-01

    The production of virulence factors by many pathogenic microorganisms depends on the intercellular communication system called quorum sensing, which involves the production and release of signal molecules known as autoinducers. Based on this, new-therapeutic strategies have emerged for the treatment of a variety of infections, such as the enzymatic degradation of signaling molecules, known as quorum quenching (QQ). In this study, we present the screening of QQ activity amongst 450 strains isolated from a bivalve hatchery in Granada (Spain), and the selection of the strain PQQ-42, which degrades a wide range of N-acylhomoserine lactones (AHLs). The selected strain, identified as Alteromonas stellipolaris, degraded the accumulation of AHLs and reduced the production of protease and chitinase and swimming motility of a Vibrio species in co-cultivation experiments in vitro. In the bio-control experiment, strain PQQ-42 significantly reduced the pathogenicity of Vibrio mediterranei VibC-Oc-097 upon the coral Oculina patagonica showing a lower degree of tissue damage (29.25 ± 14.63%) in its presence, compared to when the coral was infected with V. mediterranei VibC-Oc-097 alone (77.53 ± 13.22%). Our results suggest that this AHL-degrading bacterium may have biotechnological applications in aquaculture. PMID:27242684

  8. Selection of the N-Acylhomoserine Lactone-Degrading Bacterium Alteromonas stellipolaris PQQ-42 and of Its Potential for Biocontrol in Aquaculture.

    PubMed

    Torres, Marta; Rubio-Portillo, Esther; Antón, Josefa; Ramos-Esplá, Alfonso A; Quesada, Emilia; Llamas, Inmaculada

    2016-01-01

    The production of virulence factors by many pathogenic microorganisms depends on the intercellular communication system called quorum sensing, which involves the production and release of signal molecules known as autoinducers. Based on this, new-therapeutic strategies have emerged for the treatment of a variety of infections, such as the enzymatic degradation of signaling molecules, known as quorum quenching (QQ). In this study, we present the screening of QQ activity amongst 450 strains isolated from a bivalve hatchery in Granada (Spain), and the selection of the strain PQQ-42, which degrades a wide range of N-acylhomoserine lactones (AHLs). The selected strain, identified as Alteromonas stellipolaris, degraded the accumulation of AHLs and reduced the production of protease and chitinase and swimming motility of a Vibrio species in co-cultivation experiments in vitro. In the bio-control experiment, strain PQQ-42 significantly reduced the pathogenicity of Vibrio mediterranei VibC-Oc-097 upon the coral Oculina patagonica showing a lower degree of tissue damage (29.25 ± 14.63%) in its presence, compared to when the coral was infected with V. mediterranei VibC-Oc-097 alone (77.53 ± 13.22%). Our results suggest that this AHL-degrading bacterium may have biotechnological applications in aquaculture.

  9. Responses of the Microalga Chlorophyta sp. to Bacterial Quorum Sensing Molecules (N-Acylhomoserine Lactones): Aromatic Protein-Induced Self-Aggregation.

    PubMed

    Zhou, Dandan; Zhang, Chaofan; Fu, Liang; Xu, Liang; Cui, Xiaochun; Li, Qingcheng; Crittenden, John C

    2017-03-21

    Bacteria and microalgae often coexist during the recycling of microalgal bioresources in wastewater treatment processes. Although the bacteria may compete with the microalgae for nutrients, they could also facilitate microalgal harvesting by forming algal-bacterial aggregates. However, very little is known about interspecies interactions between bacteria and microalgae. In this study, we investigated the responses of a model microalga, Chlorophyta sp., to the typical quorum sensing (QS) molecules N-acylhomoserine lactones (AHLs) extracted from activated sludge bacteria. Chlorophyta sp. self-aggregated in 200 μm bioflocs by secreting 460-1000 kDa aromatic proteins upon interacting with AHLs, and the settling efficiency of Chlorophyta sp. reached as high as 41%. However, Chlorophyta sp. cells were essentially in a free suspension in the absence of AHLs. Fluorescence intensity of the aromatic proteins had significant (P < 0.05) relationship with the Chlorophyta sp. settleability, and showed a positive correlation, indicating that aromatic proteins helped aggregate microalga. Transcriptome results further revealed up-regulation of synthesis pathways for aromatic proteins from tyrosine and phenylalanine that was assisted by anthranilate accumulation. To the best of our knowledge, this is the first study to confirm that eukaryotic microorganisms can sense and respond to prokaryotic QS molecules.

  10. Characterization of N-acyl homoserine lactones (AHLs) producing bacteria isolated from vacuum-packaged refrigerated turbot (Scophthalmus maximus) and possible influence of exogenous AHLs on bacterial phenotype.

    PubMed

    Zhang, Caili; Zhu, Suqin; Jatt, Abdul-Nabi; Zeng, Mingyong

    2016-01-01

    Quorum sensing (QS) is a cell-to-cell communication mechanism through which microbial cells communicate and regulate their wide variety of biological activities. N-acyl homoserine lactones (AHLs) are considered to be the most important QS signaling molecules produced by several Gram-negative bacteria. The present study aimed to screen the AHLs-producing bacteria from spoiled vacuum-packaged refrigerated turbot (Scophthalmus maximus) by biosensor assays, and the profiles of AHLs produced by these bacteria were determined using reversed-phase thin-layer chromatography (RP-TLC) and gas chromatography-mass spectrometry (GC-MS). Effects of exogenous AHLs and QS inhibitor (QSI) on the phenotypes (i.e., extracellular proteolytic activity and biofilm formation) of the AHLs-producing bacteria were also evaluated. Our results demonstrated that eight out of twenty-two isolates were found to produce AHLs. Three of the AHLs-producing isolates were identified as Serratia sp., and the other five were found to belong to the family of Aeromonas. Two isolates (i.e., S. liquefaciens A2 and A. sobria B1) with higher AHLs-producing activities were selected for further studies. Mainly, RP-TLC and GC-MS analysis revealed three AHLs, i.e., 3-oxo-C6-HSL, C8-HSL and C10-HSL were produced by S. liquefaciens A2, while five AHLs, i.e., C4-HSL, C6-HSL, C8-HSL, C10-HSL, and C12-HSL, were produced by A. sobria B1. Moreover, production of AHLs in both bacterial strains were found to be density-dependent, and the AHLs activity reached a maximum level in their middle logarithmic phase and decreased in the stationary phase. The addition of exogenous AHLs and QSI decreased the specific protease activity both of the Serratia A2 and Aeromonas B1. Exogenous AHLs inhibited the biofilm formation of Serratia A2 while it enhanced the biofilm formation in Aeromonas B1. QSI inhibited the specific protease activity and biofilm formation in both bacterial strains.

  11. Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: Co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia

    PubMed Central

    2011-01-01

    Background Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novel N-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest. Results By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the genera Acinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. Conclusions Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community. PMID:21385437

  12. Functional characterization of a soybean growth stimulator Bradyrhizobium sp. strain SR-6 showing acylhomoserine lactone production.

    PubMed

    Ali, Amanat; Ayesha; Hameed, Sohail; Imran, Asma; Iqbal, Mazhar; Iqbal, Javed; Oresnik, Ivan J

    2016-09-01

    A soybean nodule endophytic bacterium Bradyrhizobium sp. strain SR-6 was characterized for production of acyl homoserine lactones (AHLs) as quorum sensing molecules. Mass spectrometry analysis of AHLs revealed the presence of C6-HSL, 3OH-C6-HSL, C8-HSL, C10-HSL, 3oxoC10-HSL, 3oxo-C12-HSL and 3OH-C12-HSL which are significantly different from those reported earlier in soybean symbionts. Purified AHL extracts significantly improved wheat and soybean seedling growth and root hair development along with increased soybean nodulation under axenic conditions. A positive correlation was observed among in vivo nitrogenase and catalase enzyme activities of the strain SR-6. Transmission electron microscopic analysis showed the cytochemical localization of catalase activity within the bacteroids, specifically attached to the peribacteroidal membrane. Root and nodule colonization proved rhizosphere competence of SR-6. The inoculation of SR-6 resulted in increased shoot length (13%), plant dry matter (50%), grain weight (16%), seed yield (20%) and N-uptake (14%) as compared to non-inoculated soybean plants. The symbiotic bacterium SR-6 has potential to improve soybean growth and yield in sub-humid climate of Azad Jammu and Kashmir region of Pakistan. The production and mass spectrometric profiling of AHLs as well as in vivo cytochemical localization of catalase enzyme activity in soybean Bradyrhizobium sp. have never been reported earlier elsewhere before our these investigations.

  13. BpiB05, a novel metagenome-derived hydrolase acting on N-acylhomoserine lactones.

    PubMed

    Bijtenhoorn, P; Schipper, C; Hornung, C; Quitschau, M; Grond, S; Weiland, N; Streit, W R

    2011-08-20

    The N-acyl-homoserine lactones (N-AHLs) play an important role in bacterial cell-cell signaling. Up to date, however, only a few different experimentally proven classes of N-AHL ring-cleaving enzymes are known. Here we report on the isolation and biochemical characterization of a novel hydrolase derived from the soil metagenome and acting on N-AHLs. The identified protein designated BpiB05 is weakly similar to hypothetical proteins from Bacteroides fragilis, the draft genomes of two Burkholderia species as well as a marine metagenomic ORF but is otherwise not similar to any known protein. BpiB05 was overexpressed in Escherichia coli as a 10× His-tagged fusion protein. The recombinant protein revealed a molecular weight of about 70kDa and was tested for its quorum quenching (QQ) activities using a lacZ-bioassay. Additional HPLC-MS analyses confirmed the lactonolytic activity of the purified protein in the presence of Ca²⁺. Further tests suggested that BpiB05 strongly reduces motility in Pseudomonas aeruginosa, pyocyanin synthesis and biofilm formation in this microbe. Because BpiB05 is not distantly related to any of the currently known hydrolases it forms probably a novel group within the growing number of proteins acting on N-AHLs. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Lack of AHL-based quorum sensing in Pseudomonas fluorescens isolated from milk.

    PubMed

    Martins, Maurilio L; Pinto, Uelinton M; Riedel, Kathrin; Vanetti, Maria C D; Mantovani, Hilário C; de Araújo, Elza F

    2014-01-01

    Numerous bacteria coordinate gene expression in response to small signalling molecules in many cases known as acylhomoserine lactones (AHLs), which accumulate as a function of cell density in a process known as quorum sensing. This work aimed to determine if phenotypes that are important to define microbial activity in foods such as biofilm formation, swarming motility and proteolytic activity of two Pseudomonas fluorescens strains, isolated from refrigerated raw milk, are influenced by AHL molecules. The tested P. fluorescens strains did not produce AHL molecules in none of the evaluated media. We found that biofilm formation was dependent on the culture media, but it was not influenced by AHLs. Our results indicate that biofilm formation, swarming motility and proteolytic activity of the tested P. fluorescens strains are not regulated by acyl-homoserine lactones. It is likely that AHL-dependent quorum sensing system is absent from these strains.

  15. Short Chain N-Acylhomoserine Lactone Production by Clinical Multidrug Resistant Klebsiella pneumoniae Strain CSG20

    PubMed Central

    Ngeow, Yun Fong; Cheng, Huey Jia; Chen, Jian Woon; Yin, Wai-Fong; Chan, Kok-Gan

    2013-01-01

    Klebsiella pneumoniae is one of the most common Gram-negative bacterial pathogens in clinical practice. It is associated with a wide range of disorders, ranging from superficial skin and soft tissue infections to potentially fatal sepsis in the lungs and blood stream. Quorum sensing, or bacterial cell-cell communication, refers to population density-dependent gene expression modulation. Quorum sensing in Proteobacteria relies on the production and sensing of signaling molecules which are mostly N-acylhomoserine lactones. Here, we report the identification of a multidrug resistant clinical isolate, K. pneumoniae strain CSG20, using matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. We further confirmed quorum sensing activity in this strain with the use of high resolution tandem liquid chromatography quadrupole mass spectrometry and provided evidence K. pneumoniae strain CSG20 produced N-hexanoyl-homoserine lactone (C6-HSL). To the best of our knowledge, this is the first report on the production of N-hexanoylhomoserine lactone (C6-HSL) in clinical isolate K. pneumoniae. PMID:24284772

  16. Short chain N-acylhomoserine lactone production by clinical multidrug resistant Klebsiella pneumoniae strain CSG20.

    PubMed

    Ngeow, Yun Fong; Cheng, Huey Jia; Chen, Jian Woon; Yin, Wai-Fong; Chan, Kok-Gan

    2013-11-07

    Klebsiella pneumoniae is one of the most common Gram-negative bacterial pathogens in clinical practice. It is associated with a wide range of disorders, ranging from superficial skin and soft tissue infections to potentially fatal sepsis in the lungs and blood stream. Quorum sensing, or bacterial cell-cell communication, refers to population density-dependent gene expression modulation. Quorum sensing in Proteobacteria relies on the production and sensing of signaling molecules which are mostly N-acylhomoserine lactones. Here, we report the identification of a multidrug resistant clinical isolate, K. pneumoniae strain CSG20, using matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. We further confirmed quorum sensing activity in this strain with the use of high resolution tandem liquid chromatography quadrupole mass spectrometry and provided evidence K. pneumoniae strain CSG20 produced N-hexanoyl-homoserine lactone (C6-HSL). To the best of our knowledge, this is the first report on the production of N-hexanoylhomoserine lactone (C6-HSL) in clinical isolate K. pneumoniae.

  17. Deciphering Physiological Functions of AHL Quorum Quenching Acylases

    PubMed Central

    Utari, Putri D.; Vogel, Jan; Quax, Wim J.

    2017-01-01

    N-Acylhomoserine lactone (AHL)-acylase (also known as amidase or amidohydrolase) is a class of enzyme that belongs to the Ntn-hydrolase superfamily. As the name implies, AHL-acylases are capable of hydrolysing AHLs, the most studied signaling molecules for quorum sensing in Gram-negative bacteria. Enzymatic degradation of AHLs can be beneficial in attenuating bacterial virulence, which can be exploited as a novel approach to fight infection of human pathogens, phytopathogens or aquaculture-related contaminations. Numerous acylases from both prokaryotic and eukaryotic sources have been characterized and tested for the interference of quorum sensing-regulated functions. The existence of AHL-acylases in a multitude of organisms from various ecological niches, raises the question of what the physiological roles of AHL-acylases actually are. In this review, we attempt to bring together recent studies to extend our understanding of the biological functions of these enzymes in nature. PMID:28674525

  18. Involvement of Acylated Homoserine Lactones (AHLs) of Aeromonas sobria in Spoilage of Refrigerated Turbot (Scophthalmus maximus L.)

    PubMed Central

    Li, Tingting; Cui, Fangchao; Bai, Fengling; Zhao, Guohua; Li, Jianrong

    2016-01-01

    One quorum sensing strain was isolated from spoiled turbot. The species was determined by 16S rRNA gene analysis and classical tests, named Aeromonas sobria AS7. Quorum-sensing (QS) signals (N-acyl homoserine lactones (AHLs)) were detected by report strains and their structures were further determined by GC-MS. The activity changes of AHLs on strain growth stage as well as the influence of different culture conditions on secretion activity of AHLs were studied by the punch method. The result indicated that strain AS7 could induce report strains to produce typical phenotypic response. N-butanoyl-dl-homoserine lactone (C4–HSL), N-hexanoyl-dl-homoserine lactone (C6–HSL), N-octanoyl-dl-homoserine lactone (C8–HSL), N-decanoyl-dl-homoserine lactone (C10–HSL), N-dodecanoyl-dl-homoserine lactone (C12–HSL) could be detected. The activities of AHLs were density-dependent and the max secretion level was at pH 8, sucrose culture, 1% NaCl and 32 h, respectively. The production of siderophore in strain AS7 was regulated by exogenous C8–HSL, rather than C6–HSL. Exogenous C4–HSL and C8–HSL accelerated the growth rate and population density of AS7 in turbot samples under refrigerated storage. However, according to the total viable counts and total volatile basic nitrogen (TVB-N) values of the fish samples, exogenous C6–HSL did not cause spoilage of the turbot fillets. In conclusion, our results suggested that QS was involved in the spoilage of refrigerated turbot. PMID:27420072

  19. The Plant Pathogen Pantoea ananatis Produces N-Acylhomoserine Lactone and Causes Center Rot Disease of Onion by Quorum Sensing▿

    PubMed Central

    Morohoshi, Tomohiro; Nakamura, Yuta; Yamazaki, Go; Ishida, Akio; Kato, Norihiro; Ikeda, Tsukasa

    2007-01-01

    A number of gram-negative bacteria have a quorum-sensing system and produce N-acyl-l-homoserine lactone (AHL) that they use them as a quorum-sensing signal molecule. Pantoea ananatis is reported as a common colonist of wheat heads at ripening and causes center rot of onion. In this study, we demonstrated that P. ananatis SK-1 produced two AHLs, N-hexanoyl-l-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl)-l-homoserine lactone (3-oxo-C6-HSL). We cloned the AHL-synthase gene (eanI) and AHL-receptor gene (eanR) and revealed that the deduced amino acid sequence of EanI/EanR showed high identity to those of EsaI/EsaR from P. stewartii. EanR repressed the ean box sequence and the addition of AHLs resulted in derepression of ean box. Inactivation of the chromosomal eanI gene in SK-1 caused disruption of exopolysaccharide (EPS) biosynthesis, biofilm formation, and infection of onion leaves, which were recovered by adding exogenous 3-oxo-C6-HSL. These results demonstrated that the quorum-sensing system involved the biosynthesis of EPS, biofilm formation, and infection of onion leaves in P. ananatis SK-1. PMID:17827290

  20. Metabolism of Acyl-Homoserine Lactone Quorum-Sensing Signals by Variovorax paradoxus

    PubMed Central

    Leadbetter, Jared R.; Greenberg, E. P.

    2000-01-01

    Acyl-homoserine lactones (acyl-HSLs) serve as dedicated cell-to-cell signaling molecules in many species of the class Proteobacteria. We have addressed the question of whether these compounds can be degraded biologically. A motile, rod-shaped bacterium was isolated from soil based upon its ability to utilize N-(3-oxohexanoyl)-l-homoserine lactone as the sole source of energy and nitrogen. The bacterium was classified as a strain of Variovorax paradoxus. The V. paradoxus isolate was capable of growth on all of the acyl-HSLs tested. The molar growth yields correlated with the length of the acyl group. HSL, a product of acyl-HSL metabolism, was used as a nitrogen source, but not as an energy source. Cleavage and partial mineralization of the HSL ring were demonstrated by using radiolabeled substrate. This study indicates that some strains of V. paradoxus degrade and grow on acyl-HSL signals as the sole energy and nitrogen sources. This study provides clues about the metabolic pathway of acyl-HSL degradation by V. paradoxus. PMID:11092851

  1. Metabolism of acyl-homoserine lactone quorum-sensing signals by Variovorax paradoxus.

    PubMed

    Leadbetter, J R; Greenberg, E P

    2000-12-01

    Acyl-homoserine lactones (acyl-HSLs) serve as dedicated cell-to-cell signaling molecules in many species of the class Proteobacteria. We have addressed the question of whether these compounds can be degraded biologically. A motile, rod-shaped bacterium was isolated from soil based upon its ability to utilize N-(3-oxohexanoyl)-L-homoserine lactone as the sole source of energy and nitrogen. The bacterium was classified as a strain of Variovorax paradoxus. The V. paradoxus isolate was capable of growth on all of the acyl-HSLs tested. The molar growth yields correlated with the length of the acyl group. HSL, a product of acyl-HSL metabolism, was used as a nitrogen source, but not as an energy source. Cleavage and partial mineralization of the HSL ring were demonstrated by using radiolabeled substrate. This study indicates that some strains of V. paradoxus degrade and grow on acyl-HSL signals as the sole energy and nitrogen sources. This study provides clues about the metabolic pathway of acyl-HSL degradation by V. paradoxus.

  2. Involvement of N-acylhomoserine lactones throughout plant infection by Erwinia carotovora subsp. atroseptica (Pectobacterium atrosepticum).

    PubMed

    Smadja, Bruno; Latour, Xavier; Faure, Denis; Chevalier, Sylvie; Dessaux, Yves; Orange, Nicole

    2004-11-01

    Erwinia carotovora subsp. atroseptica is responsible for potato blackleg disease in the field and tuber soft rot during crop storage. The process leading to the disease occurs in two phases: a primary invasion step followed by a maceration step. Bacteria-to-bacteria communication is associated with a quorum-sensing (QS) process based on the production of N-acylhomoserine lactones (HSL). The role of HSL throughout plant infection was analyzed. To this purpose, HSL produced by a specific E. carotovora subsp. atroseptica wild-type strain, which was particularly virulent on potato, were identified. A derivative of this strain that expressed an HSL lactonase gene and produced low amounts of HSL was generated. The comparison of these strains allowed the evaluation of the role of HSL and QS in disease establishment and development. Bacterial growth and motility; activity of proteins secreted by type I, II, and III systems; and hypersensitive and maceration reactions were evaluated. Results indicated that HSL production and QS regulate only those traits involved in the second stage of the host plant infection (i.e., tissue maceration) and hypersensitive response in nonhost tobacco plants. Therefore, the use of QS quenching strategies for biological control in E. carotovora subsp. atroseptica cannot prevent initial infection and multiplication of this pathogen.

  3. Evolution of Acyl-Substrate Recognition by a Family of Acyl-Homoserine Lactone Synthases

    PubMed Central

    Christensen, Quin H.; Brecht, Ryan M.; Dudekula, Dastagiri; Greenberg, E. Peter; Nagarajan, Rajesh

    2014-01-01

    Members of the LuxI protein family catalyze synthesis of acyl-homoserine lactone (acyl-HSL) quorum sensing signals from S-adenosyl-L-methionine and an acyl thioester. Some LuxI family members prefer acyl-CoA, and others prefer acyl-acyl carrier protein (ACP) as the acyl-thioester substrate. We sought to understand the evolutionary history and mechanisms mediating this substrate preference. Our phylogenetic and motif analysis of the LuxI acyl-HSL synthase family indicates that the acyl-CoA-utilizing enzymes evolved from an acyl-ACP-utilizing ancestor. To further understand how acyl-ACPs and acyl-CoAs are recognized by acyl-HSL synthases we studied BmaI1, an octanoyl-ACP-dependent LuxI family member from Burkholderia mallei, and BjaI, an isovaleryl-CoA-dependent LuxI family member from Bradyrhizobium japonicum. We synthesized thioether analogs of their thioester acyl-substrates to probe recognition of the acyl-phosphopantetheine moiety common to both acyl-ACP and acyl-CoA substrates. The kinetics of catalysis and inhibition of these enzymes indicate that they recognize the acyl-phosphopantetheine moiety and they recognize non-preferred substrates with this moiety. We find that CoA substrate utilization arose through exaptation of acyl-phosphopantetheine recognition in this enzyme family. PMID:25401334

  4. RNase E affects the expression of the acyl-homoserine lactone synthase gene sinI in Sinorhizobium meliloti.

    PubMed

    Baumgardt, Kathrin; Charoenpanich, Pornsri; McIntosh, Matthew; Schikora, Adam; Stein, Elke; Thalmann, Sebastian; Kogel, Karl-Heinz; Klug, Gabriele; Becker, Anke; Evguenieva-Hackenberg, Elena

    2014-04-01

    Quorum sensing of Sinorhizobium meliloti relies on N-acyl-homoserine lactones (AHLs) as autoinducers. AHL production increases at high population density, and this depends on the AHL synthase SinI and two transcriptional regulators, SinR and ExpR. Our study demonstrates that ectopic expression of the gene rne, coding for RNase E, an endoribonuclease that is probably essential for growth, prevents the accumulation of AHLs at detectable levels. The ectopic rne expression led to a higher level of rne mRNA and a lower level of sinI mRNA independently of the presence of ExpR, the AHL receptor, and AHLs. In line with this, IPTG (isopropyl-β-D-thiogalactopyranoside)-induced overexpression of rne resulted in a shorter half-life of sinI mRNA and a strong reduction of AHL accumulation. Moreover, using translational sinI-egfp fusions, we found that sinI expression is specifically decreased upon induced overexpression of rne, independently of the presence of the global posttranscriptional regulator Hfq. The 28-nucleotide 5' untranslated region (UTR) of sinI mRNA was sufficient for this effect. Random amplification of 5' cDNA ends (5'-RACE) analyses revealed a potential RNase E cleavage site at position +24 between the Shine-Dalgarno site and the translation start site. We postulate therefore that RNase E-dependent degradation of sinI mRNA from the 5' end is one of the steps mediating a high turnover of sinI mRNA, which allows the Sin quorum-sensing system to respond rapidly to changes in transcriptional control of AHL production.

  5. Iron limitation enhances acyl homoserine lactone (AHL) production and biofilm formation in clinical isolates of Acinetobacter baumannii

    PubMed Central

    Modarresi, Farzan; Azizi, Omid; Shakibaie, Mohammad Reza; Motamedifar, Mohammad; Mosadegh, Ellahe; Mansouri, Shahla

    2015-01-01

    Abstract Acinetobacter baumannii is an important source of infections in intensive care units (ICUs) of our hospitals in Kerman, Iran and the most frequently isolated strains produce biofilm. There is a little information about role of iron (Fe) levels on acyl homoserine lactone (AHL) production and biofilm formation in this microorganism. In the present study, we investigated the influence of iron-III limitation on AHL, siderophore, catechol and virulence factors in the biofilm forming clinical strains of A. baumannii. A total of 65 non-duplicated multidrug resistance (MDR) strains of A. baumannii were isolated from patients in ICUs of 2 hospitals in Kerman, Iran. Antibiotic susceptibility, siderophore and other iron chelators, hemolysis, cell twitching motility, capsule, gelatinase and DNase were studied. Presence of quorum sensing, LuxI and LuxR genes was detected by multiplex-PCR. AHL activity quantified by colorimetric method and the functional groups were determined by Fourier Transform Infra-Red Spectroscopy (FT-IR). Biofilm formation was detected by microtiter plate technique. All of the isolates were resistant to third generation of cephalosporins, ciprofloxacin, levofloxacin, tetracycline, whereas, 78% and 81% were resistant to amikacin and carbapenems, respectively. The siderophore activity was highest at 20 μM Fe3+ (70%); however, it decreased to 45% as concentration of Fe3+ increased to 80 μM. Furthermore, screening of the isolates for LuxI and LuxR genes showed that presence of both genes required in the isolates with high AHL activity. FT-IR analysis indicated C=O bond of the lactone ring and primary amides. Significantly, a higher amount of AHL (70%) was detected in the presence of low concentration of iron-III (20 μM); as iron concentration increased to 80 μM, the AHL activity was reduced to 40% (P ≤ 0.05). All the isolates exhibited twitching motility and had a capsule. No any gelatinase or DNase activity was detected. Quantification of

  6. Iron limitation enhances acyl homoserine lactone (AHL) production and biofilm formation in clinical isolates of Acinetobacter baumannii.

    PubMed

    Modarresi, Farzan; Azizi, Omid; Shakibaie, Mohammad Reza; Motamedifar, Mohammad; Mosadegh, Ellahe; Mansouri, Shahla

    2015-01-01

    Acinetobacter baumannii is an important source of infections in intensive care units (ICUs) of our hospitals in Kerman, Iran and the most frequently isolated strains produce biofilm. There is a little information about role of iron (Fe) levels on acyl homoserine lactone (AHL) production and biofilm formation in this microorganism. In the present study, we investigated the influence of iron-III limitation on AHL, siderophore, catechol and virulence factors in the biofilm forming clinical strains of A. baumannii. A total of 65 non-duplicated multidrug resistance (MDR) strains of A. baumannii were isolated from patients in ICUs of 2 hospitals in Kerman, Iran. Antibiotic susceptibility, siderophore and other iron chelators, hemolysis, cell twitching motility, capsule, gelatinase and DNase were studied. Presence of quorum sensing, LuxI and LuxR genes was detected by multiplex-PCR. AHL activity quantified by colorimetric method and the functional groups were determined by Fourier Transform Infra-Red Spectroscopy (FT-IR). Biofilm formation was detected by microtiter plate technique. All of the isolates were resistant to third generation of cephalosporins, ciprofloxacin, levofloxacin, tetracycline, whereas, 78% and 81% were resistant to amikacin and carbapenems, respectively. The siderophore activity was highest at 20 μM Fe(3+) (70%); however, it decreased to 45% as concentration of Fe(3+) increased to 80 μM. Furthermore, screening of the isolates for LuxI and LuxR genes showed that presence of both genes required in the isolates with high AHL activity. FT-IR analysis indicated C=O bond of the lactone ring and primary amides. Significantly, a higher amount of AHL (70%) was detected in the presence of low concentration of iron-III (20 μM); as iron concentration increased to 80 μM, the AHL activity was reduced to 40% (P ≤ 0.05). All the isolates exhibited twitching motility and had a capsule. No any gelatinase or DNase activity was detected. Quantification of the

  7. Modulation of Quorum Sensing in Acylhomoserine Lactone-Producing or -Degrading Tobacco Plants Leads to Alteration of Induced Systemic Resistance Elicited by the Rhizobacterium Serratia marcescens 90-166.

    PubMed

    Ryu, Choong-Min; Choi, Hye Kyung; Lee, Chi-Ho; Murphy, John F; Lee, Jung-Kee; Kloepper, Joseph W

    2013-06-01

    Numerous root-associated bacteria (rhizobacteria) are known to elicit induced systemic resistance (ISR) in plants. Bacterial cell-density-dependent quorum sensing (QS) is thought to be important for ISR. Here, we investigated the role of QS in the ISR elicited by the rhizobacterium, Serratia marcescens strain 90-166, in tobacco. Since S. marcescens 90-166 produces at least three QS signals, QS-mediated ISR in strain 90-166 has been difficult to understand. Therefore, we investigated the ISR capacity of two transgenic tobacco (Nicotiana tabacum) plants that contained either bacterial acylhomoserine lactone-producing (AHL) or -degrading (AiiA) genes in conjunction with S. marcescens 90-166 to induce resistance against bacterial and viral pathogens. Root application of S. marcescens 90-166 increased ISR to the bacterial pathogens, Pectobacterium carotovorum subsp. carotovorum and Pseudomonas syringae pv. tabaci, in AHL plants and decreased ISR in AiiA plants. In contrast, ISR to Cucumber mosaic virus was reduced in AHL plants treated with S. marcescens 90-166 but enhanced in AiiA plants. Taken together, these data indicate that QS-dependent ISR is elicited by S. marcescens 90-166 in a pathogen-dependent manner. This study provides insight into QS-dependent ISR in tobacco elicited by S. marcescens 90-166.

  8. Modulation of Quorum Sensing in Acylhomoserine Lactone-Producing or -Degrading Tobacco Plants Leads to Alteration of Induced Systemic Resistance Elicited by the Rhizobacterium Serratia marcescens 90-166

    PubMed Central

    Ryu, Choong-Min; Choi, Hye Kyung; Lee, Chi-Ho; Murphy, John F.; Lee, Jung-Kee; Kloepper, Joseph W.

    2013-01-01

    Numerous root-associated bacteria (rhizobacteria) are known to elicit induced systemic resistance (ISR) in plants. Bacterial cell-density-dependent quorum sensing (QS) is thought to be important for ISR. Here, we investigated the role of QS in the ISR elicited by the rhizobacterium, Serratia marcescens strain 90–166, in tobacco. Since S. marcescens 90–166 produces at least three QS signals, QS-mediated ISR in strain 90–166 has been difficult to understand. Therefore, we investigated the ISR capacity of two transgenic tobacco (Nicotiana tabacum) plants that contained either bacterial acylhomoserine lactone-producing (AHL) or -degrading (AiiA) genes in conjunction with S. marcescens 90–166 to induce resistance against bacterial and viral pathogens. Root application of S. marcescens 90–166 increased ISR to the bacterial pathogens, Pectobacterium carotovorum subsp. carotovorum and Pseudomonas syringae pv. tabaci, in AHL plants and decreased ISR in AiiA plants. In contrast, ISR to Cucumber mosaic virus was reduced in AHL plants treated with S. marcescens 90–166 but enhanced in AiiA plants. Taken together, these data indicate that QS-dependent ISR is elicited by S. marcescens 90–166 in a pathogen-dependent manner. This study provides insight into QS-dependent ISR in tobacco elicited by S. marcescens 90–166. PMID:25288945

  9. Acyl-homoserine lactones from Erwinia psidii R. IBSBF 435T, a guava phytopathogen (Psidium guajava L.).

    PubMed

    Pomini, Armando M; Manfio, Gilson P; Araújo, Welington L; Marsaioli, Anita J

    2005-08-10

    The phytopathogen Erwinia psidii R. IBSBF 435T causes rot in branches, flowers, and fruits of guava (Psidium guajava L.), being responsible for crop losses, and has no effective control. It was demonstrated that this strain produces two compounds [S-(-)-N-hexanoyl and N-heptanoyl-homoserine lactone], both belonging to the class of quorum-sensing signaling substances. A protocol using gas chromatography-flame ionization detection with chiral stationary phase is described for the absolute configuration determination of a natural acyl-homoserine lactone. Biological assays with specific reporter and synthesis of identified substances are also described. This is the first report on the N-heptanoyl-homoserine lactone occurrence in the Erwinia genus.

  10. Development of an extraction method and LC-MS analysis for N-acylated-l-homoserine lactones (AHLs) in wastewater treatment biofilms.

    PubMed

    Wang, Jinfeng; Ding, Lili; Li, Kan; Schmieder, Wilhelm; Geng, Jinju; Xu, Ke; Zhang, Yan; Ren, Hongqiang

    2017-01-15

    N-Acylated-l-homoserine lactones (AHLs) play a vital role in Gram-negative bacteria communication by promoting the formation of extracellular polymeric substances (EPS) and biofilms. However, the low concentration of these AHL signals makes the process difficult to understand. A robust and sensitive pretreatment method for AHL detection was developed in this work. Compared with eight different solid-phase extraction (SPE) columns and three various solid extraction method, we found that the UE (ultrasonic extraction) and an Oasis hydrophilic-lipophilic-balanced (HLB) sorbent in column format combined with ultra-performance liquid chromatography linked to tandem mass spectrometry (UPLC-MS/MS) can be successfully used for systematic pretreating moving bed biofilm reactor (MBBR) biological samples to extract AHLs and determine concentration of AHLs in wastewater treatment biofilms. This easy-to-follow protocol makes it ideal for quantitative analyses of AHLs in wastewater treatment biofilms.

  11. Characterization of a novel thermostable N-acylhomoserine lactonase from the thermophilic bacterium Thermaerobacter marianensis.

    PubMed

    Morohoshi, Tomohiro; Tominaga, Yoshiaki; Someya, Nobutaka; Ikeda, Tsukasa

    2015-07-01

    Thermaerobacter marianensis is an extremely thermophilic bacterium, which was isolated from the Mariana Trench, with an optimal growth temperature of approximately 75 °C. N-Acylhomoserine lactone (AHL) is a quorum-sensing signal molecule used by many gram-negative bacteria. Here, we report the identification of an AHL-degrading gene homolog (designated aiiT) in the genome of T. marianensis JCM 10246. AiiT has 59.7%, 21.2%, and 11.2% identity to AhlS from Solibacillus silvestris, AiiA from Bacillus cereus, and AidC from Chryseobacterium sp., respectively. Homologs of aiiT were also found in Thermaerobacter nagasakiensis, T. composti, and T. subterraneus. A purified AiiT-maltose binding fusion showed high AHL-degrading activity against N-hexanoyl-L-homoserine lactone, N-octanoyl-L-homoserine lactone, and N-decanoyl-L-homoserine lactone at temperatures ranging from 40 to 80 °C. HPLC analysis revealed that AiiT functions as an AHL-lactonase that catalyzes AHL ring opening by hydrolyzing lactones. AiiT displayed maximal activity at high temperatures (60-80 °C) and showed higher thermostability than other AHL lactonases.

  12. LuxR homolog-independent gene regulation by acyl-homoserine lactones in Pseudomonas aeruginosa

    PubMed Central

    Chugani, Sudha; Greenberg, Everett Peter

    2010-01-01

    Pseudomonas aeruginosa quorum control of gene expression involves three LuxR-type signal receptors LasR, RhlR, and QscR that respond to the LasI- and RhlI-generated acyl-homoserine lactone (acyl-HSL) signals 3OC12-HSL and C4-HSL. We found that a LasR-RhlR-QscR triple mutant responds to acyl-HSLs by regulating at least 37 genes. LuxR homolog-independent activation of the representative genes antA and catB also occurs in the wild type. Expression of antA was influenced the most by C10-HSL and to a lesser extent by other acyl-HSLs, including the P. aeruginosa 3OC12-HSL and C4-HSL signals. The ant and cat operons encode enzymes for the degradation of anthranilate to tricarboxylic acid cycle intermediates. Our results indicate that LuxR homolog-independent acyl-HSL control of the ant and cat operons occurs via regulation of antR, which codes for the transcriptional activator of the ant operon. Although P. aeruginosa has multiple pathways for anthranilate synthesis, one pathway—the kynurenine pathway for tryptophan degradation—is required for acyl-HSL activation of the ant operon. The kynurenine pathway is also the critical source of anthranilate for energy metabolism via the antABC gene products, as well as the source of anthranilate for synthesis of the P. aeruginosa quinolone signal. Our discovery of LuxR homolog-independent responses to acyl-HSLs provides insight into acyl-HSL signaling. PMID:20498077

  13. N-acylhomoserine lactones involved in quorum sensing control the type VI secretion system, biofilm formation, protease production, and in vivo virulence in a clinical isolate of Aeromonas hydrophila.

    PubMed

    Khajanchi, Bijay K; Sha, Jian; Kozlova, Elena V; Erova, Tatiana E; Suarez, Giovanni; Sierra, Johanna C; Popov, Vsevolod L; Horneman, Amy J; Chopra, Ashok K

    2009-11-01

    In this study, we delineated the role of N-acylhomoserine lactone(s) (AHLs)-mediated quorum sensing (QS) in the virulence of diarrhoeal isolate SSU of Aeromonas hydrophila by generating a double knockout Delta ahyRI mutant. Protease production was substantially reduced in the Delta ahyRI mutant when compared with that in the wild-type (WT) strain. Importantly, based on Western blot analysis, the Delta ahyRI mutant was unable to secrete type VI secretion system (T6SS)-associated effectors, namely haemolysin coregulated protein and the valine-glycine repeat family of proteins, while significant levels of these effectors were detected in the culture supernatant of the WT A. hydrophila. In contrast, the production and translocation of the type III secretion system (T3SS) effector AexU in human colonic epithelial cells were not affected when the ahyRI genes were deleted. Solid surface-associated biofilm formation was significantly reduced in the Delta ahyRI mutant when compared with that in the WT strain, as determined by a crystal violet staining assay. Scanning electron microscopic observations revealed that the Delta ahyRI mutant was also defective in the formation of structured biofilm, as it was less filamentous and produced a distinct exopolysaccharide on its surface when compared with the structured biofilm produced by the WT strain. These effects of AhyRI could be complemented either by expressing the ahyRI genes in trans or by the exogeneous addition of AHLs to the Delta ahyRI/ahyR(+) complemented strain. In a mouse lethality experiment, 50 % attenuation was observed when we deleted the ahyRI genes from the parental strain of A. hydrophila. Together, our data suggest that AHL-mediated QS modulates the virulence of A. hydrophila SSU by regulating the T6SS, metalloprotease production and biofilm formation.

  14. Genomic Analysis Reveals Versatile Organisms for Quorum Quenching Enzymes: Acyl-Homoserine Lactone-Acylase and -Lactonase

    PubMed Central

    Kalia, Vipin Chandra; Raju, Sajan C; Purohit, Hemant J

    2011-01-01

    Microbial virulence and their resistance to multiple drugs have obliged researchers to look for novel drug targets. Virulence of pathogenic microbes is regulated by signal molecules such as acylated homoserine lactone (AHL) produced during a cell density dependent phenomenon of quorum sensing (QS). In contrast, certain microbes produce AHL-lactonases and -acylases to degrade QS signals, also termed as quorum quenching. Mining sequenced genome databases has revealed organisms possessing conserved domains for AHL-lactonases and –acylases: i) Streptomyces (Actinobacteria), ii) Deinococcus (Deinococcus-Thermus), iii) Hyphomonas (α-Proteobacteria), iv) Ralstonia (β-Proteobacteria), v) Photorhabdus (γ-Proteobacteria), and certain marine gamma proteobacterium. Presence of genes for both the enzymes within an organism was observed in the following: i) Deinococcus radiodurans R1, ii) Hyphomonas neptunium ATCC 15444 and iii) Photorhabdus luminescens subsp. laumondii TTO1. These observations are supported by the presence motifs for lactonase and acylase in these strains. Phylogenetic analysis and multiple sequence alignment of the gene sequences for AHL-lactonases and –acylases have revealed consensus sequences which can be used to design primers for amplifying these genes even among mixed cultures and metagenomes. Quorum quenching can be exploited to prevent food spoilage, bacterial infections and bioremediation. PMID:21660112

  15. Arthrobacter strain VAI-A utilizes acyl-homoserine lactone inactivation products and stimulates quorum signal biodegradation by Variovorax paradoxus.

    PubMed

    Flagan, Suvi; Ching, Weng-Ki; Leadbetter, Jared R

    2003-02-01

    Many Proteobacteria produce acyl-homoserine lactones (acyl-HSLs) and employ them as dedicated cell-to-cell signals in a process known as quorum sensing. Previously, Variovorax paradoxus VAI-C was shown to utilize diverse acyl-HSLs as sole sources of energy and nitrogen. We describe here the properties of a second isolate, Arthrobacter strain VAI-A, obtained from the same enrichment culture that yielded V. paradoxus VAI-C. Although strain VAI-A grew rapidly and exponentially on a number of substrates, it grew only slowly and aberrantly (i.e., linearly) in media amended with oxohexanoyl-HSL as the sole energy source. Increasing the culture pH markedly improved the growth rate in media containing this substrate but did not abolish the aberrant kinetics. The observed growth was remarkably similar to the known kinetics of the pH-influenced half-life of acyl-HSLs, which decay chemically to yield the corresponding acyl-homoserines. Strain VAI-A grew rapidly and exponentially when provided with an acyl-homoserine as the sole energy or nitrogen source. The isolate was also able to utilize HSL as a sole source of nitrogen but not as energy for growth. V. paradoxus, known to release HSL as a product of quorum signal degradation, was examined for the ability to support the growth of Arthrobacter strain VAI-A in defined cocultures. It did. Moreover, the acyl-HSL-dependent growth rate and yield of the coculture were dramatically superior to those of the monocultures. This suggested that the original coenrichment of these two organisms from the same soil sample was not coincidental and that consortia may play a role in quorum signal turnover and mineralization. The fact that Arthrobacter strain VAI-A utilizes the two known nitrogenous degradation products of acyl-HSLs, acyl-homoserine and HSL, begins to explain why none of the three compounds are known to accumulate in the environment.

  16. AmiE, a novel N-acylhomoserine lactone acylase belonging to the amidase family, from the activated-sludge isolate Acinetobacter sp. strain Ooi24.

    PubMed

    Ochiai, Seiji; Yasumoto, Sera; Morohoshi, Tomohiro; Ikeda, Tsukasa

    2014-11-01

    Many Gram-negative bacteria use N-acyl-l-homoserine lactones (AHLs) as quorum-sensing signal molecules. We have reported that Acinetobacter strains isolated from activated sludge have AHL-degrading activity. In this study, we cloned the amiE gene as an AHL-degradative gene from the genomic library of Acinetobacter sp. strain Ooi24. High-performance liquid chromatography analysis revealed that AmiE functions as an AHL acylase, which hydrolyzes the amide bond of AHL. AmiE showed a high level of degrading activity against AHLs with long acyl chains but no activity against AHLs with acyl chains shorter than eight carbons. AmiE showed homology with a member of the amidases (EC 3.5.1.4) but not with any known AHL acylase enzymes. An amino acid sequence of AmiE from Ooi24 showed greater than 99% identities with uncharacterized proteins from Acinetobacter ursingii CIP 107286 and Acinetobacter sp. strain CIP 102129, but it was not found in the draft or complete genome sequences of other Acinetobacter strains. The presence of transposase-like genes around the amiE genes of these three Acinetobacter strains suggests that amiE is transferred by a putative transposon. Furthermore, the expression of AmiE in Pseudomonas aeruginosa PAO1 reduced AHL accumulation and elastase activity, which were regulated by AHL-mediated quorum sensing.

  17. Isolation and characterization of N-acylhomoserine lactonase from the thermophilic bacterium, Geobacillus caldoxylosilyticus YS-8.

    PubMed

    Seo, Myung-Ji; Lee, Beom-Seon; Pyun, Yu-Ryang; Park, Hoon

    2011-01-01

    Geobacillus caldoxylosilyticus YS-8, which was isolated from volcanic soil in Indonesia, was found to degrade various N-acylhomoserine lactones (AHLs) with different lengths and acyl side-chain substitutions over a wide temperature range of 30-70 °C. The purified AHL-degrading enzyme showed a single band of 32 kDa, and its N-terminal amino acid sequence was determined to be ANVIKARPKLYVMDN, tentatively suggesting that the AHL-degrading enzyme was AHL lactonase. The AHL-degrading activity of the purified enzyme was maximized at pH 7.5 and 50 °C, and it retained about 50% of its activity even after a heat treatment at 60 °C for 3 h, exhibiting properties consistent with a thermostable enzyme. The mass spectrometric analysis demonstrated that the AHL-degrading enzyme catalyzed lactone ring opening of N-3-oxohexanoyl-L-homoserine lactone and N-hexanoyl-L-homoserine lactone by hydrolyzing the lactones and working as an AHL lactonase.

  18. Identification of Unanticipated and Novel N-Acyl L-Homoserine Lactones (AHLs) Using a Sensitive Non-Targeted LC-MS/MS Method

    PubMed Central

    Patel, Nishaben M.; Moore, Joseph D.; Blackwell, Helen E.; Amador-Noguez, Daniel

    2016-01-01

    N-acyl L-homoserine lactones (AHLs) constitute a predominant class of quorum-sensing signaling molecules used by Gram-negative bacteria. Here, we report a sensitive and non-targeted HPLC-MS/MS method based on parallel reaction monitoring (PRM) to identify and quantitate known, unanticipated, and novel AHLs in microbial samples. Using a hybrid quadrupole-high resolution mass analyzer, this method integrates MS scans and all-ion fragmentation MS/MS scans to allow simultaneous detection of AHL parent-ion masses and generation of full mass spectra at high resolution and high mass accuracy in a single chromatographic run. We applied this method to screen for AHL production in a variety of Gram-negative bacteria (i.e. B. cepacia, E. tarda, E. carotovora, E. herbicola, P. stewartii, P. aeruginosa, P. aureofaciens, and R. sphaeroides) and discovered that nearly all of them produce a larger set of AHLs than previously reported. Furthermore, we identified production of an uncommon AHL (i.e. 3-oxo-C7-HL) in E. carotovora and P. stewartii, whose production has only been previously observed within the genera Serratia and Yersinia. Finally, we used our method to quantitate AHL degradation in B. cepacia, E. carotovora, E. herbicola, P. stewartii, P. aeruginosa, P. aureofaciens, the non-AHL producer E. coli, and the Gram-positive bacterium B. subtilis. We found that AHL degradation ability varies widely across these microbes, of which B. subtilis and E. carotovora are the best degraders, and observed that there is a general trend for AHLs containing long acyl chains (≥10 carbons) to be degraded at faster rates than AHLs with short acyl chains (≤6 carbons). PMID:27706219

  19. Quorum sensing in Aeromonas hydrophila and Aeromonas salmonicida: identification of the LuxRI homologs AhyRI and AsaRI and their cognate N-acylhomoserine lactone signal molecules.

    PubMed Central

    Swift, S; Karlyshev, A V; Fish, L; Durant, E L; Winson, M K; Chhabra, S R; Williams, P; Macintyre, S; Stewart, G S

    1997-01-01

    Spent culture supernatants from both Aeromonas hydrophila and Aeromonas salmonicida activate a range of biosensors responsive to N-acylhomoserine lactones (AHLs). The genes for a quorum sensing signal generator and a response regulator were cloned from each Aeromonas species and termed ahyRI and asaRI, respectively. Protein sequence homology analysis places the gene products within the growing family of LuxRI homologs. ahyR and asaR are transcribed divergently from ahyI and asaI, respectively, and in both Aeromonas species, the genes downstream have been identified by DNA sequence and PCR analysis. Downstream of both ahyI and asaI is a gene with close homology to iciA, an inhibitor of chromosome replication in Escherichia coli, a finding which implies that in Aeromonas, cell division may be linked to quorum sensing. The major signal molecule synthesized via both AhyI and AsaI was purified from spent culture supernatants and identified as N-(butanoyl)-L-homoserine lactone (BHL) by thin-layer chromatography, high-pressure liquid chromatography analysis, and mass spectrometry. In addition, a second, minor AHL, N-hexanoyl-L-homoserine lactone, was identified. Transcriptional reporter studies with ahyI::luxCDABE fusions indicate that AhyR and BHL are both required for ahyI transcription. For A. salmonicida, although the addition of exogenous BHL gives only a small stimulation of the production of serine protease with comparison to the control culture, the incorporation of a longer-chain AHL, N-(3-oxodecanoyl)-L-homoserine lactone, reduced the final level (by approximately 50%) and delayed the appearance (from an A650 of 0.9 in the control to an A650 of 1.2 in the test) of protease in the culture supernatant. These data add A. hydrophila and A. salmonicida to the growing family of gram-negative bacteria now known to control gene expression through quorum sensing. PMID:9286976

  20. The hydrolysis of unsubstituted N-acylhomoserine lactones to their homoserine metabolites. Analytical approaches using ultra performance liquid chromatography.

    PubMed

    Englmann, Matthias; Fekete, Agnes; Kuttler, Christina; Frommberger, Moritz; Li, Xiaojing; Gebefügi, Istvan; Fekete, Jenoe; Schmitt-Kopplin, Philippe

    2007-08-10

    Derivatives of N-acylhomoserine lactones (HSLs) with different alkanoyl side chains occur as quorum or diffusion sensing molecules in gram-negative bacteria and their quantitative chemical analysis became important as a possible way to follow regulation processes of their pathogenicity towards plants and animals. The lactone-ring of HSLs is chemically and biologically not stable: the corresponding serines can be formed in alkaline conditions and these may presumably behave inactive for the biological system. A fast and MS compatible liquid chromatographic method applying high pressure (ultra performance liquid chromatography) with diode array detection was optimized for the rapid quantitative determination of HSLs and their corresponding hydrolysis products. The technique was used to follow and model the hydrolysis reactions of HSLs as function of pH under controlled conditions. Moreover, the method could be triggered to allow a confirmation in the assignment of the potential HSLs in real samples by analysis of the real samples before and after hydrolysis. Quantitative performance characteristics and the character of the hydrolysis reaction were studied as well. The optimized method was successfully applied to a bacterial culture supernatant real sample containing HSLs.

  1. Quorum Quenching: Enzymatic Disruption of N-Acylhomoserine Lactone-Mediated Bacterial Communication in Burkholderia thailandensis

    DTIC Science & Technology

    2004-10-01

    strain (with the exception of RU02, which was grown for 48 h) was cultured on R2A agar plates (BiOLOG) with the appropriate antibiotics for 24 h at 37°C...caused the hyper-beta-hemolysis of sheep erythrocytes on blood agar plates. In contrast, AHL cleavage in B. thailandensis by the Bacillus AiiA...blood agar plates. In contrast, AHL cleavage in B. thailandensis by the Bacillus AiiA lactonases failed to enhance beta-hemolytic activity. The

  2. Modelled microgravity cultivation modulates N-acylhomoserine lactone production in Rhodospirillum rubrum S1H independently of cell density.

    PubMed

    Mastroleo, Felice; Van Houdt, Rob; Atkinson, Steve; Mergeay, Max; Hendrickx, Larissa; Wattiez, Ruddy; Leys, Natalie

    2013-12-01

    The photosynthetic alphaproteobacterium Rhodospirillum rubrum S1H is part of the Micro-Ecological Life Support System Alternative (MELiSSA) project that is aiming to develop a closed life support system for oxygen, water and food production to support human life in space in forthcoming long-term space exploration missions. In the present study, R. rubrum S1H was cultured in a rotating wall vessel (RWV), simulating partial microgravity conditions on Earth. The bacterium showed a significant response to cultivation in simulated microgravity at the transcriptomic, proteomic and metabolic levels. In simulated microgravity conditions three N-acyl-l-homoserine lactones (C10-HSL, C12-HSL and 3-OH-C14-HSL) were detected in concentrations that were twice those detected under normal gravity, while no differences in cell density was detected. In addition, R. rubrum cultivated in modelled microgravity showed higher pigmentation than the normal gravity control, without change in culture oxygenation. When compared to randomized microgravity cultivation using a random positioning machine, significant overlap for the top differentially expressed genes and proteins was observed. Cultivation in this new artificial environment of simulated microgravity showed new properties of this well-known bacterium, including its first, to our knowledge, complete quorum-sensing-related N-acylhomoserine lactone profile.

  3. AHL-type quorum sensing and its regulation on symplasmata formation in Pantoea agglomerans YS19.

    PubMed

    Jiang, Jing; Wu, Suisui; Wang, Jieru; Feng, Yongjun

    2015-05-01

    Pantoea agglomerans YS19, an endophytic diazotrophic bacterium isolated from rice, is characterized by the formation of multicellular aggregate structure called symplasmata, which not only bestow the strong stress-resistance of the bacterium, but also contribute to the specific adaptation in the endophyte-host association. Acyl-homoserine lactones (AHLs), as the important signal molecule in the quorum sensing (QS) system of gram-negative bacteria, were demonstrated to regulate motility, cell-aggregation, and other bacterial behaviors. Here, the production of AHL by P. agglomerans YS19 and its regulation on the symplasmata formation were studied. It was revealed that the production of AHL by YS19 was initiated at the exponential growth stage and from then on, reached the peak values at the stationary growth stage in LB medium. The AHL was identified as N-3-oxooctanoyl-L-homoserine lactone (OOHL) by MALDI-TOF-MS analysis. The AHL synthesis gene pagI and receptor gene pagR in YS19 were cloned and phylogenetic analysis showed that they were high conservative among strains in species of P. agglomerans. It was revealed that AHL promoted the bacterial growth and symplasmata formation of YS19. Meanwhile, the colonization ability and growth-promoting effect of YS19 on the host plant were also enhanced by AHL. These results strongly suggest the pleiotropic effects of the AHL-type QS system in endophytic life of the strain. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Interference of Quorum Sensing by Delftia sp. VM4 Depends on the Activity of a Novel N-Acylhomoserine Lactone-Acylase

    PubMed Central

    Maisuria, Vimal B.; Nerurkar, Anuradha S.

    2015-01-01

    Background Turf soil bacterial isolate Delftia sp. VM4 can degrade exogenous N-acyl homoserine lactone (AHL), hence it effectively attenuates the virulence of bacterial soft rot pathogen Pectobacterium carotovorum subsp. carotovorum strain BR1 (Pcc BR1) as a consequence of quorum sensing inhibition. Methodology/Principal Findings Isolated Delftia sp. VM4 can grow in minimal medium supplemented with AHL as a sole source of carbon and energy. It also possesses the ability to degrade various AHL molecules in a short time interval. Delftia sp. VM4 suppresses AHL accumulation and the production of virulence determinant enzymes by Pcc BR1 without interference of the growth during co-culture cultivation. The quorum quenching activity was lost after the treatment with trypsin and proteinase K. The protein with quorum quenching activity was purified by three step process. Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) and Mass spectrometry (MS/MS) analysis revealed that the AHL degrading enzyme (82 kDa) demonstrates homology with the NCBI database hypothetical protein (Daci_4366) of D. acidovorans SPH-1. The purified AHL acylase of Delftia sp. VM4 demonstrated optimum activity at 20–40°C and pH 6.2 as well as AHL acylase type mode of action. It possesses similarity with an α/β-hydrolase fold protein, which makes it unique among the known AHL acylases with domains of the N-terminal nucleophile (Ntn)-hydrolase superfamily. In addition, the kinetic and thermodynamic parameters for hydrolysis of the different AHL substrates by purified AHL-acylase were estimated. Here we present the studies that investigate the mode of action and kinetics of AHL-degradation by purified AHL acylase from Delftia sp. VM4. Significance We characterized an AHL-inactivating enzyme from Delftia sp. VM4, identified as AHL acylase showing distinctive similarity with α/β-hydrolase fold protein, described its biochemical and thermodynamic properties for the first time and

  5. Complete Genome Sequence of Chryseobacterium sp. Strain StRB126, an N-Acylhomoserine Lactone-Degrading Bacterium Isolated from Potato Root

    PubMed Central

    Wang, Wen-Zhao; Someya, Nobutaka; Ikeda, Tsukasa

    2014-01-01

    Chryseobacterium sp. strain StRB126 was isolated from a potato root and showed N-acylhomoserine lactone-degrading activity. Here, we present the complete 5,503,743-bp genome sequence of StRB126, which has a G+C content of 35.6% and carries 4,828 protein-coding genes, six rRNA operons, and 80 tRNA genes. PMID:25291777

  6. Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.

    PubMed

    Elasri, M; Delorme, S; Lemanceau, P; Stewart, G; Laue, B; Glickmann, E; Oger, P M; Dessaux, Y

    2001-03-01

    A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N-acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL, N-hexanoyl-L-homoserine lactone, N-(3-oxo-hexanoyl)-homoserine lactone, and N-(3-oxo-octanoyl)-L-homoserine lactone (no absolute correlation between genomospecies of P. syringae and their ability to produce NAHL could be found). Six strains of fluorescent pseudomonads, belonging to the species P. chlororaphis, P. fluorescens, and P. putida, isolated from the plant rhizosphere produced different types of NAHL. In contrast, none of the strains isolated from soil samples were shown to produce NAHL. The gene encoding the NAHL synthase in P. syringae pv. maculicola was isolated by complementation of an NAHL-deficient Chromobacterium mutant. Sequence analysis revealed the existence of a luxI homologue that we named psmI. This gene is sufficient to confer NAHL synthesis upon its bacterial host and has strong homology to psyI and ahlI, two genes involved in NAHL production in P. syringae pv. tabaci and P. syringae pv. syringae, respectively. We identified another open reading frame that we termed psmR, transcribed convergently in relation to psmI and partly overlapping psmI; this gene encodes a putative LuxR regulatory protein. This gene organization, with luxI and luxR homologues facing each other and overlapping, has been found so far only in the enteric bacteria Erwinia and Pantoea and in the related species P. syringae pv. tabaci.

  7. Unravelling the genome of long chain N-acylhomoserine lactone-producing Acinetobacter sp. strain GG2 and identification of its quorum sensing synthase gene

    PubMed Central

    How, Kah Yan; Hong, Kar-Wai; Sam, Choon-Kook; Koh, Chong-Lek; Yin, Wai-Fong; Chan, Kok-Gan

    2015-01-01

    Myriad proteobacteria use N-acyl homoserine lactone (AHL) molecules as quorum sensing (QS) signals to regulate different physiological functions, including virulence, antibiotic production, and biofilm formation. Many of these proteobacteria possess LuxI/LuxR system as the QS mechanism. Recently, we reported the 3.89 Mb genome of Acinetobacter sp. strain GG2. In this work, the genome of this long chain AHL-producing bacterium was unravelled which led to the molecular characterization of luxI homologue, designated as aciI. This 552 bp gene was cloned and overexpressed in Escherichia coli BL21(DE3). The purified protein was ∼20.5 kDa and is highly similar to several autoinducer proteins of LuxI family among Acinetobacter species. To verify the AHL synthesis activity of this protein, high-resolution liquid chromatography–mass spectrometry analysis revealed the production of 3-oxo-dodecanoyl-homoserine lactone and 3-hydroxy-dodecanoyl-homoserine lactone from induced E. coli harboring the recombinant AciI. Our data show for the first time, the cloning and characterization of the luxI homologue from Acinetobacter sp. strain GG2, and confirmation of its AHLs production. These data are of great significance as the annotated genome of strain GG2 has provided a valuable insight in the study of autoinducer molecules and its roles in QS mechanism of the bacterium. PMID:25926817

  8. Dynamics of AHL mediated quorum sensing under flow and non-flow conditions

    NASA Astrophysics Data System (ADS)

    Meyer, Andrea; Megerle, Judith A.; Kuttler, Christina; Müller, Johannes; Aguilar, Claudio; Eberl, Leo; Hense, Burkhard A.; Rädler, Joachim O.

    2012-04-01

    Quorum sensing (QS) describes the capability of microbes to communicate with each other by the aid of small molecules. Here we investigate the dynamics of QS-regulated gene expression induced by acylhomoserine lactones (AHLs) in Pseudomonas putida IsoF containing a green fluorescent protein-based AHL reporter. The fluorescence time course of individual colonies is monitored following the external addition of a defined AHL concentration to cells which had previously reached the QS-inactive state in AHL-free medium. Using a microfluidic setup the experiment is performed both under flow and non-flow conditions. We find that without supplying external AHL gene expression is induced without flow while flow suppresses the induction. Both without and with flow, at a low AHL concentration the fluorescence onset is significantly delayed while fluorescence starts to increase directly upon the addition of AHL at a high concentration. The differences between no flow and flow can be accounted for using a two-compartment model. This indicates AHL accumulation in a volume which is not affected by the flow. The experiments furthermore show significant cell-to-cell and colony-to-colony variability which is discussed in the context of a compartmentalized QS mechanism.

  9. Analysis of N-acylhomoserine lactones after alkaline hydrolysis and anion-exchange solid-phase extraction by capillary zone electrophoresis-mass spectrometry.

    PubMed

    Frommberger, Moritz; Hertkorn, Norbert; Englmann, Matthias; Jakoby, Sarah; Hartmann, Anton; Kettrup, Antonius; Schmitt-Kopplin, Philippe

    2005-04-01

    A quantitative, specific, and sensitive method for the determination of N-acylhomoserine lactones (HSLs - a group of bacterial semiochemicals) in the form of their hydrolysis products (N-acylhomoserines, HSs) is presented. Real samples were analyzed by capillary zone electrophoresis-mass spectrometry (CZE-MS) after alkaline lactonolysis and extraction by mixed-mode anion-exchange solid-phase extraction. The presented cleanup significantly speeds up the HSL extraction procedure, strongly reduces sample consumption, and is more selective compared to the commonly used liquid/liquid extraction. Completeness of the hydrolysis reaction was examined by nuclear magnetic resonance spectroscopy. This CZE-MS method complements recently published capillary separation techniques (nano liquid chromatography-MS, partial-filling micellar electrokinetic chromatography-MS, gas chromatography-MS) and provides a possibility to differentiate quantitatively between the homoserines (as naturally occurring degradation products) besides the intact homoserine lactones. The method was found to be quantitative down to a concentration of 0.05 microg/mL (limit of quantification), while the limit of detection was determined with 0.01 microg/mL - sufficient for the analysis of culture supernatants.

  10. GacS-dependent regulation of enzymic and antifungal activities and synthesis of N-acylhomoserine lactones in rhizospheric strain Pseudomonas chlororaphis 449.

    PubMed

    Veselova, M; Lipasova, V; Protsenko, M A; Buza, N; Khmel, I A

    2009-09-01

    Pseudomonas chlororaphis strain 449 isolated from the rhizosphere of maize suppresses numerous plant pathogens in vitro. The strain produces phenazine antibiotics and synthesizes at least three types of quorum sensing signaling molecules, N-acylhomoserine lactones. Here we have shown that the rhizospheric P. chlororaphis strains 449, well known strain 30-84 as well as two other P. chlororaphis strains exhibit polygalacturonase activity. Using mini-Tn5 transposon mutagenesis, four independent mutants of strain P. chlororaphis 449 with insertion of mini-Tn5 Km2 in gene gacS of two-component GacA-GacS system of global regulation were selected. All these mutant strains were deficient in production of extracellular proteinase(s), phenazines, N-acylhomoserine lactones synthesis, and did not inhibit the growth of G(+) bacteria in comparison with the wild type strain. The P. chlororaphis 449-06 gacS (-) mutant studied in greater detail was deficient in polygalacturonase, pectin methylesterase activities, swarming motility and antifungal activity. It is the first time the involvement of GacA-GacS system in the regulation of enzymes of pectin metabolism, polygalacturonase and pectin methylesterase, was demonstrated in fluorescent pseudomonads.

  11. An RpoS (sigmaS) homologue regulates acylhomoserine lactone-dependent autoinduction in Ralstonia solanacearum.

    PubMed

    Flavier, A B; Schell, M A; Denny, T P

    1998-05-01

    Many bacteria sense an appropriate growth condition or a critical population density for gene expression by producing acylhomoserine lactones (acyl-HSLs) that act as intercellular autoinduction signals. We recently showed that, in Ralstonia (Pseudomonas) solanacearum, a phytopathogenic bacterium, acyl-HSL production requires soll, which encodes a putative acyl-HSL synthase, and that its expression is positively regulated by the acyl-HSL-responsive SolR transcriptional regulator. This acyl-HSL-dependent autoinduction system is noteworthy because (i) it is regulated by a 'higher level' autoinducer system (responsive to 3-hydroxypalmitic acid methyl ester) via PhcA, a LysR-type transcriptional regulator and (ii) acyl-HSL production requires two additional unlinked loci. As reported here, cloning and sequencing of one of these other loci revealed that it encodes a homologue of RpoS, an alternative sigma factor (sigmaS) that in other bacteria activates gene expression during stationary phase or in response to stress conditions. R. solanacearum RpoS (RpoS(Rso)) was demonstrated to function as a sigma factor because when introduced in trans into an Escherichia coli rpoS mutant it largely restored expression of the RpoS-dependent bolAp1 gene. Mutation of rpoS(Rso) in R. solanacearum reduced survival during starvation and low pH conditions, but did not affect survival during exposure to hydrogen peroxide, high osmolarity or high temperature. This mutant was also altered in its production of several virulence factors and wilted tomato plants several days more slowly than the wild-type parent. Transcription of solR and soll were decreased in an rpoS(Rso) background (thereby reducing acyl-HSL production), but neither mutations in solR, soll or phcA nor addition of acyl-HSLs affected rpoS(Rso) expression. Therefore, in R. solanacearum the acyl-HSL-dependent autoinduction system is controlled both by a second autoinduction system and by the RpoS(Rso) sigma factor.

  12. AidC, a novel N-acylhomoserine lactonase from the potato root-associated cytophaga-flavobacteria-bacteroides (CFB) group bacterium Chryseobacterium sp. strain StRB126.

    PubMed

    Wang, Wen-Zhao; Morohoshi, Tomohiro; Someya, Nobutaka; Ikeda, Tsukasa

    2012-11-01

    N-acylhomoserine lactones (AHLs) are used as quorum-sensing (QS) signal molecules by many gram-negative bacteria. We have reported that Chryseobacterium sp. strain StRB126, which was isolated from the root surface of potato, has AHL-degrading activity. In this study, we cloned and characterized the aidC gene from the genomic library of StRB126. AidC has AHL-degrading activity and shows homology to several metallo-β-lactamase proteins from Bacteroidetes, although not to any known AHL-degrading enzymes. Purified AidC, as a maltose-binding fusion protein, showed high degrading activity against all tested AHLs, whether short- or long-chain forms, with or without substitution at carbon 3. High-performance liquid chromatography (HPLC) analysis revealed that AidC functions as an AHL lactonase catalyzing AHL ring opening by hydrolyzing lactones. An assay to determine the effects of covalent and ionic bonding showed that Zn(2+) is important to AidC activity both in vitro and in vivo. In addition, the aidC gene could also be PCR amplified from several other Chryseobacterium strains. In conclusion, this study indicated that the aidC gene, encoding a novel AHL lactonase, may be widespread throughout the genus Chryseobacterium. Our results extend the diversity and known bacterial hosts of AHL-degrading enzymes.

  13. AidC, a Novel N-Acylhomoserine Lactonase from the Potato Root-Associated Cytophaga-Flavobacteria-Bacteroides (CFB) Group Bacterium Chryseobacterium sp. Strain StRB126

    PubMed Central

    Wang, Wen-Zhao; Someya, Nobutaka; Ikeda, Tsukasa

    2012-01-01

    N-Acylhomoserine lactones (AHLs) are used as quorum-sensing (QS) signal molecules by many Gram-negative bacteria. We have reported that Chryseobacterium sp. strain StRB126, which was isolated from the root surface of potato, has AHL-degrading activity. In this study, we cloned and characterized the aidC gene from the genomic library of StRB126. AidC has AHL-degrading activity and shows homology to several metallo-β-lactamase proteins from Bacteroidetes, although not to any known AHL-degrading enzymes. Purified AidC, as a maltose-binding fusion protein, showed high degrading activity against all tested AHLs, whether short- or long-chain forms, with or without substitution at carbon 3. High-performance liquid chromatography (HPLC) analysis revealed that AidC functions as an AHL lactonase catalyzing AHL ring opening by hydrolyzing lactones. An assay to determine the effects of covalent and ionic bonding showed that Zn2+ is important to AidC activity both in vitro and in vivo. In addition, the aidC gene could also be PCR amplified from several other Chryseobacterium strains. In conclusion, this study indicated that the aidC gene, encoding a novel AHL lactonase, may be widespread throughout the genus Chryseobacterium. Our results extend the diversity and known bacterial hosts of AHL-degrading enzymes. PMID:22941089

  14. Profile of Citrobacter freundii ST2, a Multi-acyl-homoserine Lactone Producer Associated with Marine Dinoflagellates.

    PubMed

    Huang, Xinqi; Gao, Yan; Ma, Zhiping; Lin, Guanghui; Cai, Zhonghua; Zhou, Jin

    2017-01-01

    Marine algae provide a unique niche termed the phycosphere for microorganism inhabitation. The phycosphere environment is an important niche for mutualistic and competitive interactions between algae and bacteria. Quorum sensing (QS) serves as a gene regulatory system in the microbial biosphere that allows bacteria to sense the population density with signaling molecules, such as acyl-homoserine lactone (AHL), and adapt their physiological activities to their surroundings. Understanding the QS system is important to elucidate the interactions between algal-associated microbial communities in the phycosphere condition. In this study, we isolated an epidermal bacterium (ST2) from the marine dinoflagellate Scrippsiella trochoidea and evaluated its AHL production profile. Strain ST2 was classified as a member of the genus Citrobacter closely related to Citrobacter freundii by 16S rRNA gene sequence analysis. Thin-layer chromatography revealed that C. freundii ST2 secreted three active AHL compounds into the culture supernatant. Specific compounds, such as N-butyryl-L-homoserine lactone (C4-AHL), N-octanoyl-DL-homoserine lactone (C8-AHL), and N-decanoyl-DL-homoserine lactone (C10-AHL), were identified by high-resolution tandem mass spectrometry. Carbon metabolic profiling with Biolog EcoPlate™ indicated that C. freundii ST2 was widely used as a carbon source and preferred carbohydrates, amino acids, and carboxylic acids as carbon substrates. Our results demonstrated that C. freundii ST2 is a multi-AHL producer that participates in the phycosphere carbon cycle.

  15. Combined Effects of Curcumin and (-)-Epigallocatechin Gallate on Inhibition of N-Acylhomoserine Lactone-Mediated Biofilm Formation in Wastewater Bacteria from Membrane Bioreactor.

    PubMed

    Lade, Harshad; Paul, Diby; Kweon, Ji Hyang

    2015-11-01

    This work investigated the potential of curcumin (CCM) and (-)-epigallocatechin gallate (EGCG) to inhibit N-acyl homoserine lactone (AHL)-mediated biofilm formation in gramnegative bacteria from membrane bioreactor (MBR) activated sludge. The minimum inhibitory concentrations (MICs) of CCM alone against all the tested bacteria were 200-350 μg/ml, whereas those for EGCG were 300-600 μg/ml. Biofilm formation at one-half MICs indicated that CCM and EGCG alone respectively inhibited 52-68% and 59-78% of biofilm formation among all the tested bacteria. However, their combination resulted in 95-99% of biofilm reduction. Quorum sensing inhibition (QSI) assay with known biosensor strains demonstrated that CCM inhibited the expression of C4 and C6 homoserine lactones (HSLs)-mediated phenotypes, whereas EGCG inhibited C4, C6, and C10 HSLs-based phenotypes. The Center for Disease Control biofilm reactor containing a multispecies culture of nine bacteria with onehalf MIC of CCM (150 μg/ml) and EGCG (275 μg/ml) showed 17 and 14 μg/cm(2) of extracellular polymeric substances (EPS) on polyvinylidene fluoride membrane surface, whereas their combination (100 μg/ml of each) exhibited much lower EPS content (3 μg/cm(2)). Confocal laser scanning microscopy observations also illustrated that the combination of compounds tremendously reduced the biofilm thickness. The combined effect of CCM with EGCG clearly reveals for the first time the enhanced inhibition of AHL-mediated biofilm formation in bacteria from activated sludge. Thus, such combined natural QSI approach could be used for the inhibition of membrane biofouling in MBRs treating wastewaters.

  16. Isolation of AHL-degrading bacteria from micro-algal cultures and their impact on algal growth and on virulence of Vibrio campbellii to prawn larvae.

    PubMed

    Pande, Gde Sasmita Julyantoro; Natrah, Fatin Mohd Ikhsan; Flandez, Ace Vincent Bravo; Kumar, Uday; Niu, Yufeng; Bossier, Peter; Defoirdt, Tom

    2015-12-01

    Inactivation of quorum sensing (QS) signal molecules, such as acylhomoserine lactones (AHLs) of pathogenic bacteria, has been proposed as a novel method to combat bacterial diseases in aquaculture. Despite the importance of micro-algae for aquaculture, AHL degradation by bacteria associated with micro-algal cultures has thus far not been investigated. In this study, we isolated Pseudomonas sp. NFMI-T and Bacillus sp. NFMI-C from open cultures of the micro-algae Tetraselmis suecica and Chaetoceros muelleri, respectively. An AHL degradation assay showed that either monocultures or co-cultures of the isolates were able to degrade the AHL N-hexanoyl-L-homoserine lactone. In contrast, only Bacillus sp. NFMI-C was able to inactivate N-hydroxybutanoyl-L-homoserine lactone, the AHL produced by Vibrio campbellii. The isolated bacteria were able to persist for up to 3 weeks in conventionalized micro-algal cultures, indicating that they were able to establish and maintain themselves within open algal cultures. Using gnotobiotic algal cultures, we found that the isolates did not affect growth of the micro-algae from which they were isolated, whereas a mixture of both isolates increased the growth of Tetraselmis and decreased the growth of Chaetoceros. Finally, addition of Bacillus sp. NFMI-C to the rearing water of giant river prawn (Macrobrachium rosenbergii) larvae significantly improved survival of the larvae when challenged with pathogenic V. campbellii, whereas it had no effect on larval growth.

  17. Non-antibiotic quorum sensing inhibitors acting against N-acyl homoserine lactone synthase as druggable target

    PubMed Central

    Chang, Chien-Yi; Krishnan, Thiba; Wang, Hao; Chen, Ye; Yin, Wai-Fong; Chong, Yee-Meng; Tan, Li Ying; Chong, Teik Min; Chan, Kok-Gan

    2014-01-01

    N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography–mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach. PMID:25430794

  18. Non-antibiotic quorum sensing inhibitors acting against N-acyl homoserine lactone synthase as druggable target.

    PubMed

    Chang, Chien-Yi; Krishnan, Thiba; Wang, Hao; Chen, Ye; Yin, Wai-Fong; Chong, Yee-Meng; Tan, Li Ying; Chong, Teik Min; Chan, Kok-Gan

    2014-11-28

    N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography-mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach.

  19. Theoretical and structural analysis of the active site of the transcriptional regulators LasR and TraR, using molecular docking methodology for identifying potential analogues of acyl homoserine lactones (AHLs) with anti-quorum sensing activity.

    PubMed

    Ahumedo, Maicol; Díaz, Antonio; Vivas-Reyes, Ricardo

    2010-02-01

    In the present study the homology of transcriptional receptors LuxR type were evaluated using as point of reference the receptors TraR and LasR of the bacterial types Agrobacterium tumefaciens and Pseudomonas aureginosa respectively. A series of alignments were performed in order to demonstrate that the active site of the protein is conserved in wide range of gram negative bacteria. Moreover, some docking calculations were carried out for analogs of the acyl homoserin lactones (AHLs) and regulatory proteins LasR and TraR, to understand the complex microenvironment in which the ligands are exposed. The molecular alignments show clearly that there are preserved motifs in the residues (Y53, Y61, W57, D70, W85 to TraR, Y56, Y64, W60, D73, W88 to LasR) analyzed, which may serve as site-specific targets for the development of potential antagonists. In this study was found that the anti-quorum sensing activity of the AHLs molecular analogs appears to depend on; the structure of the lactone ring and on appropriate combination of absolute and relative stereochemistry of the carbonyl (C=O) and amide (NH(2)) groups of the side chain of these AHLs molecular analogs, in combination with the interactions with the conserved amino acids (D73, W60, Y56, S129 to LasR and D70, W57, Y53 to TraR) of the LuxR type protein family.

  20. Acyl-homoserine lactone binding to and stability of the orphan Pseudomonas aeruginosa quorum-sensing signal receptor QscR.

    PubMed

    Oinuma, Ken-Ichi; Greenberg, E Peter

    2011-01-01

    The Pseudomonas aeruginosa transcription factor QscR responds to a variety of fatty acyl-homoserine lactones (HSLs), including N-3-oxododecanoyl-HSL (3OC12-HSL), which is produced and detected by the P. aeruginosa quorum-sensing circuit LasI and LasR. As is true for LasR and many other acyl-HSL-dependent transcription factors, production of soluble QscR in sufficient amounts for purification requires growth of recombinant bacteria in the presence of an appropriate acyl-HSL. QscR is thought to bind 3OC12-HSL relatively weakly compared to LasR, and unlike LasR, binding of purified QscR to target DNA was shown to strongly depend on exogenously added 3OC12-HSL. We show that purified QscR is dimeric at sufficiently high concentrations and monomeric at lower concentrations. Furthermore, QscR bound 3OC12-HSL more tightly than previously believed. Purified QscR retained 3OC12-HSL, and at sufficiently high concentrations, it bound target DNA in the absence of added 3OC12-HSL. We also obtained soluble QscR from recombinant Escherichia coli grown in the presence of N-3-oxohexanoyl-HSL (3OC6-HSL) instead of 3OC12-HSL, and because 3OC6-HSL bound much more loosely to QscR than other acyl-HSLs tested, we were able to exchange 3OC6-HSL with other acyl-HSLs in vitro and then estimate binding affinities of QscR for different acyl-HSLs and for target DNA. Our data support a model whereby QscR polypeptides fold properly in the absence of an acyl-HSL, but soluble, acyl-HSL-free QscR does not accumulate because it is subject to rapid aggregation or proteolysis.

  1. Croceicoccus naphthovorans sp. nov., a polycyclic aromatic hydrocarbons-degrading and acylhomoserine-lactone-producing bacterium isolated from marine biofilm, and emended description of the genus Croceicoccus.

    PubMed

    Huang, Yili; Zeng, Yanhua; Feng, Hao; Wu, Yuehong; Xu, Xuewei

    2015-05-01

    A polycyclic aromatic hydrocarbons-degrading and acylhomoserine-lactone-producing marine bacterium, designated strain PQ-2(T), was isolated from marine biofilm collected from a boat shell at a harbour of Zhoushan island in Zhejiang Province, PR China. Strain PQ-2(T) is Gram-stain-negative, yellow-pigmented, non-motile and short rod-shaped. Optimal growth of strain PQ-2(T) was observed at 32 °C, at pH 7.0 and in 2% (w/v) NaCl. The 16S rRNA gene sequence of strain PQ-2(T) showed highest similarity to Croceicoccus marinus E4A9(T) (96.3%) followed by Novosphingobium malaysiense MUSC 273(T) (95.6%) and Altererythrobacter marinus H32(T) (95.6%). Phylogenetic analysis with all species of the family Erythrobacteraceae with validly published names revealed that strain PQ-2(T) formed a phyletic line with Croceicoccus marinus E4A9(T) that was distinct from other members of the family Erythrobacteraceae . The sole respiratory quinone was ubiquinone 10 (Q-10). The predominant fatty acids were C18 : 1ω7c, C17 : 1ω6c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The genomic DNA G+C content was 61.7 mol%. In the polar lipid profile, phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol, one unidentified phospholipid and one sphingoglycolipid were the major compounds; and another sphingoglycolipid was present in a minor amount. Based on the genotypic and phenotypic data, strain PQ-2(T) represents a novel species of the genus Croceicoccus , for which the name Croceicoccus naphthovorans sp. nov. is proposed. The type strain is PQ-2(T) ( =CGMCC 1.12805(T) =NBRC 110381(T)). In addition, emended descriptions for the genus Croceicoccus and the species C. marinus are given. © 2015 IUMS.

  2. A high-throughput screen for quorum-sensing inhibitors that target acyl-homoserine lactone synthases.

    PubMed

    Christensen, Quin H; Grove, Tyler L; Booker, Squire J; Greenberg, E Peter

    2013-08-20

    Many Proteobacteria use N-acyl-homoserine lactone (acyl-HSL) quorum sensing to control specific genes. Acyl-HSL synthesis requires unique enzymes that use S-adenosyl methionine as an acyl acceptor and amino acid donor. We developed and executed an enzyme-coupled high-throughput cell-free screen to discover acyl-HSL synthase inhibitors. The three strongest inhibitors were equally active against two different acyl-HSL synthases: Burkholderia mallei BmaI1 and Yersinia pestis YspI. Two of these inhibitors showed activity in whole cells. The most potent compound behaves as a noncompetitive inhibitor with a Ki of 0.7 µM and showed activity in a cell-based assay. Quorum-sensing signal synthesis inhibitors will be useful in attempts to understand acyl-HSL synthase catalysis and as a tool in studies of quorum-sensing control of gene expression. Because acyl-HSL quorum-sensing controls virulence of some bacterial pathogens, anti-quorum-sensing chemicals have been sought as potential therapeutic agents. Our screen and identification of acyl-HSL synthase inhibitors serve as a basis for efforts to target quorum-sensing signal synthesis as an antivirulence approach.

  3. Characterisation of a marine bacterium Vibrio brasiliensis T33 producing N-acyl homoserine lactone quorum sensing molecules.

    PubMed

    Tan, Wen-Si; Yunos, Nina Yusrina Muhamad; Tan, Pui-Wan; Mohamad, Nur Izzati; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-07-08

    N-acylhomoserine lactones (AHL) plays roles as signal molecules in quorum sensing (QS) in most Gram-negative bacteria. QS regulates various physiological activities in relation with population density and concentration of signal molecules. With the aim of isolating marine water-borne bacteria that possess QS properties, we report here the preliminary screening of marine bacteria for AHL production using Chromobacterium violaceum CV026 as the AHL biosensor. Strain T33 was isolated based on preliminary AHL screening and further identified by using 16S rDNA sequence analysis as a member of the genus Vibrio closely related to Vibrio brasiliensis. The isolated Vibrio sp. strain T33 was confirmed to produce N-hexanoyl-L-homoserine lactone (C6-HSL) and N-(3-oxodecanoyl)-L-homoserine lactone (3-oxo-C10 HSL) through high resolution tandem mass spectrometry analysis. We demonstrated that this isolate formed biofilms which could be inhibited by catechin. To the best of our knowledge, this is the first report that documents the production of these AHLs by Vibrio brasiliensis strain T33.

  4. Molecular identification of aiiA homologous gene from endophytic Enterobacter species and in silico analysis of putative tertiary structure of AHL-lactonase.

    PubMed

    Rajesh, P S; Rai, V Ravishankar

    2014-01-03

    The aiiA homologous gene known to encode AHL- lactonase enzyme which hydrolyze the N-acylhomoserine lactone (AHL) quorum sensing signaling molecules produced by Gram negative bacteria. In this study, the degradation of AHL molecules was determined by cell-free lysate of endophytic Enterobacter species. The percentage of quorum quenching was confirmed and quantified by HPLC method (p<0.0001). Amplification and sequence BLAST analysis showed the presence of aiiA homologous gene in endophytic Enterobacter asburiae VT65, Enterobacter aerogenes VT66 and Enterobacter ludwigii VT70 strains. Sequence alignment analysis revealed the presence of two zinc binding sites, "HXHXDH" motif as well as tyrosine residue at the position 194. Based on known template available at Swiss-Model, putative tertiary structure of AHL-lactonase was constructed. The result showed that novel endophytic strains of Enterobacter genera encode the novel aiiA homologous gene and its structural importance for future study. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. A probable aculeacin A acylase from the Ralstonia solanacearum GMI1000 is N-acyl-homoserine lactone acylase with quorum-quenching activity.

    PubMed

    Chen, Chin-Nung; Chen, Chii-Jaan; Liao, Chen-Ting; Lee, Chia-Yin

    2009-05-09

    The infection and virulence functions of diverse plant and animal pathogens that possess quorum sensing systems are regulated by N-acylhomoserine lactones (AHLs) acting as signal molecules. AHL-acylase is a quorum quenching enzyme and degrades AHLs by removing the fatty acid side chain from the homoserine lactone ring of AHLs. This blocks AHL accumulation and pathogenic phenotypes in quorum sensing bacteria. An aac gene of undemonstrated function from Ralstonia solanacearum GMI1000 was cloned, expressed in Escherichia coli; it inactivated four AHLs that were tested. The sequence of the 795 amino acid polypeptide was considerably similar to the AHL-acylase from Ralstonia sp. XJ12B with 83% identity match and shared 39% identity with an aculeacin A acylase precursor from the gram-positive actinomycete Actinoplanes utahensis. Aculeacin A is a neutral lipopeptide antibiotic and an antifungal drug. An electrospray ionisation mass spectrometry (ESI-MS) analysis verified that Aac hydrolysed the amide bond of AHL, releasing homoserine lactone and the corresponding fatty acids. However, ESI-MS analysis demonstrated that the Aac could not catalyze the hydrolysis of the palmitoyl moiety of the aculeacin A. Moreover, the results of MIC test of aculeacin A suggest that Aac could not deacylate aculeacin A. The specificity of Aac for AHLs showed a greater preference for long acyl chains than for short acyl chains. Heterologous expression of the aac gene in Chromobacterium violaceum CV026 effectively inhibited violacein and chitinase activity, both of which were regulated by the quorum-sensing mechanism. These results indicated that Aac could control AHL-dependent pathogenicity. This is the first study to find an AHL-acylase in a phytopathogen. Our data provide direct evidence that the functioning of the aac gene (NP520668) of R. solanacearum GMI1000 is via AHL-acylase and not via aculeacin A acylase. Since Aac is a therapeutic potential quorum-quenching agent, its further

  6. AHL signaling molecules with a large acyl chain enhance biofilm formation on sulfur and metal sulfides by the bioleaching bacterium Acidithiobacillus ferrooxidans.

    PubMed

    González, Alex; Bellenberg, Sören; Mamani, Sigde; Ruiz, Lina; Echeverría, Alex; Soulère, Laurent; Doutheau, Alain; Demergasso, Cecilia; Sand, Wolfgang; Queneau, Yves; Vera, Mario; Guiliani, Nicolas

    2013-04-01

    Biofilm formation plays a pivotal role in bioleaching activities of bacteria in both industrial and natural environments. Here, by visualizing attached bacterial cells on energetic substrates with different microscopy techniques, we obtained the first direct evidence that it is possible to positively modulate biofilm formation of the extremophilic bacterium Acidithiobacillus ferrooxidans on sulfur and pyrite surfaces by using Quorum Sensing molecules of the N-acylhomoserine lactone type (AHLs). Our results revealed that AHL-signaling molecules with a long acyl chain (12 or 14 carbons) increased the adhesion of A. ferrooxidans cells to these substrates. In addition, Card-Fish experiments demonstrated that C14-AHL improved the adhesion of indigenous A. ferrooxidans cells from a mixed bioleaching community to pyrite. Finally, we demonstrated that this improvement of cell adhesion is correlated with an increased production of extracellular polymeric substances. Our results open up a promising means to develop new strategies for the improvement of bioleaching efficiency and metal recovery, which could also be used to control environmental damage caused by acid mine/rock drainage.

  7. TraI, a LuxI homologue, is responsible for production of conjugation factor, the Ti plasmid N-acylhomoserine lactone autoinducer.

    PubMed

    Hwang, I; Li, P L; Zhang, L; Piper, K R; Cook, D M; Tate, M E; Farrand, S K

    1994-05-24

    Conjugal transfer of the nopaline-type Agrobacterium Ti plasmid pTiC58 is regulated by a transcriptional activator, TraR, and a diffusible signal molecule, conjugation factor (CF). CF is a member of a family of substituted homoserine lactones (HSLs) that act as coinducers for regulating gene expression in diverse Gram-negative bacteria by a mechanism called autoinduction. In Vibrio fischeri HSL production is conferred by the luxI gene. Homologues of this gene are responsible for HSL production by other Gram-negative bacteria. A gene that we call traI, conferring production of material with CF activity, was localized to a 1-kb region at the upstream end of tra3 of pTiC58. Spectroscopy showed that the activity was authentic CF. Sequence analysis showed that traI could encode a protein of 211 amino acids, TraI, that is related to the proteins responsible for HSL production by other bacteria. A second, partial open reading frame immediately downstream of traI could encode a protein related to TrbB of plasmid RP4, which is required for conjugal transfer. Transcription of traI and of the downstream tra3 genes requires TraR and CF and initiates from the traI promoter. The results show that traI is responsible for CF production, that it is the first gene of the tra3 operon, and that expression of this operon is regulated by autoinduction.

  8. Hierarchical autoinduction in Ralstonia solanacearum: control of acyl-homoserine lactone production by a novel autoregulatory system responsive to 3-hydroxypalmitic acid methyl ester.

    PubMed

    Flavier, A B; Ganova-Raeva, L M; Schell, M A; Denny, T P

    1997-11-01

    Bacteria employ autoinduction systems to sense the onset of appropriate cell density for expression of developmental genes. In many gram-negative bacteria, autoinduction involves the production of and response to diffusible acylated-homoserine lactones (acyl-HSLs) and is mediated by members of the LuxR and LuxI families. Ralstonia (Pseudomonas) solanacearum, a phytopathogenic bacterium that appears to autoregulate its virulence genes, produces compounds that promote expression of several heterologous acyl-HSL-responsive reporter gene constructs. High-pressure liquid chromatography of highly concentrated ethyl acetate extracts revealed that culture supernatants of strain AW1 contained two compounds with retention times similar to N-hexanoyl- and N-octanoyl-HSL. To investigate the role of these acyl-HSLs in R. solanacearum virulence gene expression, transposon mutants that were deficient for inducing an acyl-HSL-responsive reporter in Agrobacterium tumefaciens were generated. Three loci involved in normal acyl-HSL production were identified, one of which was shown to contain the divergently transcribed solR and solI genes, the luxR and luxI homologs, respectively. A 4.1-kb fragment containing solR and solI enabled all of the mutants (regardless of the locus inactivated) and a naturally acyl-HSL-defective strain of R. solanacearum to produce acyl-HSLs. Inactivation of solI abolished production of all detectable acyl-HSLs but affected neither the expression of virulence genes in culture nor the ability to wilt tomato plants. AW1 has a functional autoinduction system, because (i) expression of solI required SolR and acyl-HSL and (ii) expression of a gene linked to solR and solI, designated aidA, was acyl-HSL dependent. Because AidA has no homologs in the protein databases, its discovery provided no clues as to the role of acyl-HSLs in R. solanacearum gene regulation. However, expression of solR and solI required the global LysR-type virulence regulator PhcA, and both

  9. Disruption of epithelial barrier by quorum-sensing N-3-(oxododecanoyl)-homoserine lactone is mediated by matrix metalloproteinases

    PubMed Central

    Eum, Sung Yong; Jaraki, Dima; Bertrand, Luc; András, Ibolya E.

    2014-01-01

    The intestinal epithelium forms a selective barrier maintained by tight junctions (TJs) and separating the luminal environment from the submucosal tissues. N-acylhomoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence homeostasis of the host intestinal epithelium. In the present study, we evaluated the regulatory mechanisms affecting the impact of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on barrier function of human intestinal epithelial Caco-2 cells. Treatment with C12-HSL, but not with C4-HSL, perturbed Caco-2 barrier function; the effect was associated with decreased levels of the TJ proteins occludin and tricellulin and their delocalization from the TJs. C12-HSL also induced matrix metalloprotease (MMP)-2 and MMP-3 activation via lipid raft- and protease-activated receptor (PAR)-dependent signaling. Pretreatment with lipid raft disruptors, PAR antagonists, or MMP inhibitors restored the C12-HSL-induced loss of the TJ proteins and increased permeability of Caco-2 cell monolayers. These results indicate that PAR/lipid raft-dependent MMP-2 and -3 activation followed by degradation of occludin and tricellulin are involved in C12-HSL-induced alterations of epithelial paracellular barrier functions. PMID:24742991

  10. Novel Reporter for Identification of Interference with Acyl Homoserine Lactone and Autoinducer-2 Quorum Sensing

    PubMed Central

    Weiland-Bräuer, Nancy; Pinnow, Nicole

    2014-01-01

    Two reporter strains were established to identify novel biomolecules interfering with bacterial communication (quorum sensing [QS]). The basic design of these Escherichia coli-based systems comprises a gene encoding a lethal protein fused to promoters induced in the presence of QS signal molecules. Consequently, these E. coli strains are unable to grow in the presence of the respective QS signal molecules unless a nontoxic QS-interfering compound is present. The first reporter strain designed to detect autoinducer-2 (AI-2)-interfering activities (AI2-QQ.1) contained the E. coli ccdB lethal gene under the control of the E. coli lsrA promoter. The second reporter strain (AI1-QQ.1) contained the Vibrio fischeri luxI promoter fused to the ccdB gene to detect interference with acyl-homoserine lactones. Bacteria isolated from the surfaces of several marine eukarya were screened for quorum-quenching (QQ) activities using the established reporter systems AI1-QQ.1 and AI2-QQ.1. Out of 34 isolates, two interfered with acylated homoserine lactone (AHL) signaling, five interfered with AI-2 QS signaling, and 10 were demonstrated to interfere with both signal molecules. Open reading frames (ORFs) conferring QQ activity were identified for three selected isolates (Photobacterium sp., Pseudoalteromonas sp., and Vibrio parahaemolyticus). Evaluation of the respective heterologously expressed and purified QQ proteins confirmed their ability to interfere with the AHL and AI-2 signaling processes. PMID:25527543

  11. A novel plasmid for detection of N-acyl homoserine lactones.

    PubMed

    Ling, Elizabeth A; Ellison, Matthew L; Pesci, Everett C

    2009-07-01

    Many bacteria utilize acyl-homoserine lactones as cell to cell signals that can regulate the expression of numerous genes. Structural differences in acyl-homoserine lactones produced by different bacteria, such as acyl side chain length and the presence or absence of an oxy group, make many of the commonly used detection bioassays impractical for broad range detection. Here we present a simple, broad range acyl-homoserine lactone detection bioassay that can be used to detect a wide range of these chemical signals. A plasmid (pEAL01) was constructed and transformed into Pseudomonas aeruginosa strain QSC105 to allow for detection of a broad range of acyl-homoserine lactones through induction of a lasB'-lacZ transcriptional fusion. Monitoring beta-galactosidase activity from this bioassay showed that P. aeruginosa strain QSC105 (pEAL01) could detect the presence of eight acyl-homoserine lactones tested at physiological concentrations. This novel strain could also detect acyl-homoserine lactones from the extracts of four different bacteria that produce different acyl-homoserine lactones signals. These data indicate that strain QSC105 (pEAL01) can be used to detect a wide variety of acyl-homoserine lactones by a simple beta-galactosidase assay and this bioassay could be a useful and inexpensive tool to quickly identify the presence of these signal molecules.

  12. Non-thermal Plasma Exposure Rapidly Attenuates Bacterial AHL-Dependent Quorum Sensing and Virulence

    PubMed Central

    Flynn, Padrig B.; Busetti, Alessandro; Wielogorska, Ewa; Chevallier, Olivier P.; Elliott, Christopher T.; Laverty, Garry; Gorman, Sean P.; Graham, William G.; Gilmore, Brendan F.

    2016-01-01

    The antimicrobial activity of atmospheric pressure non-thermal plasma has been exhaustively characterised, however elucidation of the interactions between biomolecules produced and utilised by bacteria and short plasma exposures are required for optimisation and clinical translation of cold plasma technology. This study characterizes the effects of non-thermal plasma exposure on acyl homoserine lactone (AHL)-dependent quorum sensing (QS). Plasma exposure of AHLs reduced the ability of such molecules to elicit a QS response in bacterial reporter strains in a dose-dependent manner. Short exposures (30–60 s) produce of a series of secondary compounds capable of eliciting a QS response, followed by the complete loss of AHL-dependent signalling following longer exposures. UPLC-MS analysis confirmed the time-dependent degradation of AHL molecules and their conversion into a series of by-products. FT-IR analysis of plasma-exposed AHLs highlighted the appearance of an OH group. In vivo assessment of the exposure of AHLs to plasma was examined using a standard in vivo model. Lettuce leaves injected with the rhlI/lasI mutant PAO-MW1 alongside plasma treated N-butyryl-homoserine lactone and n-(3-oxo-dodecanoyl)-homoserine lactone, exhibited marked attenuation of virulence. This study highlights the capacity of atmospheric pressure non-thermal plasma to modify and degrade AHL autoinducers thereby attenuating QS-dependent virulence in P. aeruginosa. PMID:27242335

  13. Non-thermal Plasma Exposure Rapidly Attenuates Bacterial AHL-Dependent Quorum Sensing and Virulence.

    PubMed

    Flynn, Padrig B; Busetti, Alessandro; Wielogorska, Ewa; Chevallier, Olivier P; Elliott, Christopher T; Laverty, Garry; Gorman, Sean P; Graham, William G; Gilmore, Brendan F

    2016-05-31

    The antimicrobial activity of atmospheric pressure non-thermal plasma has been exhaustively characterised, however elucidation of the interactions between biomolecules produced and utilised by bacteria and short plasma exposures are required for optimisation and clinical translation of cold plasma technology. This study characterizes the effects of non-thermal plasma exposure on acyl homoserine lactone (AHL)-dependent quorum sensing (QS). Plasma exposure of AHLs reduced the ability of such molecules to elicit a QS response in bacterial reporter strains in a dose-dependent manner. Short exposures (30-60 s) produce of a series of secondary compounds capable of eliciting a QS response, followed by the complete loss of AHL-dependent signalling following longer exposures. UPLC-MS analysis confirmed the time-dependent degradation of AHL molecules and their conversion into a series of by-products. FT-IR analysis of plasma-exposed AHLs highlighted the appearance of an OH group. In vivo assessment of the exposure of AHLs to plasma was examined using a standard in vivo model. Lettuce leaves injected with the rhlI/lasI mutant PAO-MW1 alongside plasma treated N-butyryl-homoserine lactone and n-(3-oxo-dodecanoyl)-homoserine lactone, exhibited marked attenuation of virulence. This study highlights the capacity of atmospheric pressure non-thermal plasma to modify and degrade AHL autoinducers thereby attenuating QS-dependent virulence in P. aeruginosa.

  14. Transgenic Amorphophallus konjac expressing synthesized acyl-homoserine lactonase (aiiA) gene exhibit enhanced resistance to soft rot disease.

    PubMed

    Ban, Huifang; Chai, Xinli; Lin, Yongjun; Zhou, Ying; Peng, Donghai; Zhou, Yi; Zou, Yulan; Yu, Ziniu; Sun, Ming

    2009-12-01

    Amorphophallus konjac is an important economic crop widely used in health products and biomaterials. However, this monocotyledonous plant's production is seriously restricted by soft rot disease. Some Bacillus thuringiensis strains generate an endocellular acyl homoserine lactonase (AiiA), which has inhibitory effect on soft rot pathogen through disrupting the signal molecules (N-acylhomoserine lactones, AHL) of their Quorum Sensing system. The aim of our study is to obtain transgenic A. konjac expressing AiiA protein and exhibiting resistance to soft rot. But till now, there is not any report about exogenous gene transformation in A. konjac. In this research, an Agrobacterium-mediated genetic transformation system was constructed. An aiiA gene was synthesized according to the codon usage in A. konjac. Embryogenic callus was infected with the A. tumefaciens strain EHA105 harboring the plant transformation plasmid pU1301 plus synthesized aiiA gene. After antibiotics screening, 34 plants were obtained. PCR analysis showed that positive amplified fragments were present in 21 out of these 34 lines. Southern blot analysis indicated that aiiA gene had integrated into the genome of A. konjac. Western blotting demonstrated that the target protein of interest was reactive with the antibody against AiiA. Further disease resistance detection revealed that all of the tested transgenic A. konjac lines exhibited high resistance to soft rot bacteria Erwinia carotovora subsp. Carotovora (Ecc) SCG1. The protocol is useful for the quality improvement of A. konjac through genetic transformation.

  15. Preliminary study on an innovative, simple mast cell-based electrochemical method for detecting foodborne pathogenic bacterial quorum signaling molecules (N-acyl-homoserine-lactones).

    PubMed

    Jiang, Donglei; Feng, Dongdong; Jiang, Hui; Yuan, Limin; Yongqi, Yin; Xu, Xin; Fang, Weiming

    2017-04-15

    This paper reports the a novel and simple mast cell-based electrochemical method for detecting of bacterial quorum signaling molecules, N-acylhomoserine lactones (AHLs), which can be utilized to preliminarily evaluate the toxicity of food-borne pathogenic bacteria. Rat basophilic leukemia (RBL-2H3) mast cells encapsulated in alginate/graphene oxide hydrogel were immobilized on a gold electrode, while mast cells as recognition elements were cultured in a 3D cell culture system. Electrochemical impedance spectroscopy (EIS) was utilized to record the cell impedance signal as-influenced by Pseudomonas aeruginosa quorum-sensing molecule, N-3-oxododecanoyl homoserine lactone (3OC12-HSL). The results indicated that cellular activities such as cell viability, apoptosis, intracellular calcium, and degranulation were markedly influenced by the AHLs. Importantly, the exposure of 3OC12-HSL to mast cells induced a marked decrease in the electrochemical impedance signal in a dose-dependent manner. The detection limit for 3OC12-HSL was 0.034μM with a linear range of 0.1-1μM. These results were confirmed via conventional cell assay and transmission electron microscope (TEM) analysis. Altogether, the proposed method appears to be an innovative and effective approach to the quantitative measurement of Gram-negative bacterial quorum signaling molecules; to this effect, it also may serve as a primary evaluation of the cytotoxicity of food-borne pathogens.

  16. Heterologous overexpression, purification, and in vitro characterization of AHL lactonases.

    PubMed

    Thomas, Pei W; Fast, Walter

    2011-01-01

    Quorum-quenching enzymes are useful as biochemical tools and possible therapeutic proteins. One of the best-characterized families of these catalysts is the N-acyl-L-homoserine lactone (AHL) lactonases, which rely on a dinuclear metal ion active site to hydrolytically cleave the autoinducer's lactone bond and inactivate signaling. A detailed understanding of how this enzyme works can help in the design of more selective and efficient reagents. To facilitate these studies, we describe a methodology to heterologously express, purify, and conduct in vitro characterization of several metalloforms of the AHL lactonase from Bacillus thuringiensis (AiiA). These procedures should be applicable to similar enzymes and will facilitate the production of more useful quorum-quenching reagents for biochemical studies and possible therapeutic applications.

  17. AHL-priming functions via oxylipin and salicylic acid

    PubMed Central

    Schenk, Sebastian T.; Schikora, Adam

    2015-01-01

    Collaborative action between the host plant and associated bacteria is crucial for the establishment of an efficient interaction. In bacteria, the synchronized behavior of a population is often achieved by a density-dependent communication called quorum sensing. This behavior is based on signaling molecules, which influence bacterial gene expression. N-acyl homoserine lactones (AHLs) are such molecules in many Gram-negative bacteria. Moreover, some AHLs are responsible for the beneficial effect of bacteria on plants, for example the long chain N-3-oxo-tetradecanoyl-L-homoserine lactone (oxo-C14-HSL) can prime Arabidopsis and barley plants for an enhanced defense. This AHL-induced resistance phenomenon, named AHL-priming, was observed in several independent laboratories during the last two decades. Very recently, the mechanism of priming with oxo-C14-HSL was shown to depend on an oxylipin and salicylic acid (SA). SA is a key element in plant defense, it accumulates during different plant resistance responses and is the base of systemic acquired resistance. In addition, SA itself can prime plants for an enhanced resistance against pathogen attack. On the other side, oxylipins, including jasmonic acid (JA) and related metabolites, are lipid-derived signaling compounds. Especially the oxidized fatty acid derivative cis-OPDA, which is the precursor of JA, is a newly described player in plant defense. Unlike the antagonistic effect of SA and JA in plant–microbe interactions, the recently described pathway functions through a synergistic effect of oxylipins and SA, and is independent of the JA signaling cascade. Interestingly, the oxo-C14-HSL-induced oxylipin/SA signaling pathway induces stomata defense responses and cell wall strengthening thus prevents pathogen invasion. In this review, we summarize the findings on AHL-priming and the related signaling cascade. In addition, we discuss the potential of AHL-induced resistance in new strategies of plant protection. PMID

  18. Labrenzia sp. BM1: A Quorum Quenching Bacterium That Degrades N-acyl Homoserine Lactones via Lactonase Activity

    PubMed Central

    Ghani, Norshazliza Ab; Norizan, Siti Nur Maisarah; Chan, Xin Yue; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    We report the degradation of quorum sensing N-acylhomoserine lactone molecules by a bacterium isolated from a Malaysian marine water sample. MALDI-TOF and phylogenetic analysis indicated this isolate BM1 clustered closely to Labrenzia sp. The quorum quenching activity of this isolate was confirmed by using a series of bioassays and rapid resolution liquid chromatography analysis. Labrenzia sp. degraded a wide range of N-acylhomoserine lactones namely N-(3-hexanoyl)-l-homoserine lactone (C6-HSL), N-(3-oxohexanoyl)-l-homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-l-homoserine lactone (3-hydroxy-C6-HSL). Re-lactonisation bioassays confirmed Labrenzia sp. BM1 degraded these signalling molecules efficiently via lactonase activity. To the best of our knowledge, this is the first documentation of a Labrenzia sp. capable of degrading N-acylhomoserine lactones and confirmation of its lactonase-based mechanism of action. PMID:24995373

  19. Purification and antibiofilm activity of AHL-lactonase from endophytic Enterobacter aerogenes VT66.

    PubMed

    Rajesh, P S; Rai, V Ravishankar

    2015-11-01

    The opportunistic pathogen Pseudomonas aeruginosa uses biofilm lifestyle to resist antibiotic treatment. In our study, endophytic bacterium Enterobacter aerogenes VT66 quenched the N-acyl homoserine lactone (AHL) molecules produced by P. aeruginosa PAO1. The quorum quenching activity was attributed to the presence of AHL-lactonase. The AHL-lactonase was purified using column chromatography and purified AHL-lactonase was applied for the control of biofilm formation in P. aeruginosa PAO1. The results showed that purified AHL-lactonase obtained with a molecular weight about 30kDa was able to inhibit more than 70% of biofilm in P. aeruginosa PAO1 (P<0.001). Antibiofilm activity of AHL-lactonase was correlated well with results from staining technique used to determine inhibition of biomass and viable cell activity. Therefore, results unambiguously confirm that the AHL-lactonase from E. aerogenes VT66 could be used as antibiofilm therapeutics in P. aeruginosa associated biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. The bacterial quorum-sensing molecule, N-3-oxo-dodecanoyl-L-homoserine lactone, inhibits mediator release and chemotaxis of murine mast cells.

    PubMed

    Khambati, Ibrahim; Han, Sangsu; Pijnenburg, Daniëlle; Jang, Hannah; Forsythe, Paul

    2017-03-01

    Bacterial colonization relies on communication between bacteria via so-called "quorum-sensing molecules", which include the acyl-homoserine lactone group. Certain acyl-homoserine lactones can modulate mammalian cell function and are thought to contribute to bacterial pathogenicity. Given the role of mast cells in host defense, we investigated the ability of acyl-homoserine lactones to modulate mast cell function. We utilized murine primary mast cell cultures to assess the effect of acyl-homoserine lactones on degranulation and cytokine release in response to different stimuli. We also assessed cell migration in response to chemoattractants. The effect of acyl-homoserine lactones in vivo was tested using a passive cutaneous anaphylaxis model. Two of the tested quorum-sensing molecules, N-3-oxo-dodecanoyl-L-homoserine lactone and N-Dodecanoyl-L-homoserine lactone, inhibited IgE dependent and independent degranulation and mediator release from primary mast cells. Further testing of N-3-oxo-dodecanoyl-L-homoserine lactone, the most potent inhibitor and a product of Pseudomonas aeruginosa, revealed that it also attenuated chemotaxis and LPS induced cytokine production. In vivo, N-3-oxo-dodecanoyl-L-homoserine lactone inhibited the passive cutaneous anaphylaxis response in mice. The ability of N-3-oxo-dodecanoyl-L-homoserine lactone to stabilize mast cells may contribute to the pathogenicity of P. aeruginosa but could potentially be exploited therapeutically in allergic disease.

  1. CsrA represses translation of sdiA, which encodes the N-acylhomoserine-L-lactone receptor of Escherichia coli, by binding exclusively within the coding region of sdiA mRNA.

    PubMed

    Yakhnin, Helen; Baker, Carol S; Berezin, Igor; Evangelista, Michael A; Rassin, Alisa; Romeo, Tony; Babitzke, Paul

    2011-11-01

    The RNA binding protein CsrA is the central component of a conserved global regulatory system that activates or represses gene expression posttranscriptionally. In every known example of CsrA-mediated translational control, CsrA binds to the 5' untranslated region of target transcripts, thereby repressing translation initiation and/or altering the stability of the RNA. Furthermore, with few exceptions, repression by CsrA involves binding directly to the Shine-Dalgarno sequence and blocking ribosome binding. sdiA encodes the quorum-sensing receptor for N-acyl-l-homoserine lactone in Escherichia coli. Because sdiA indirectly stimulates transcription of csrB, which encodes a small RNA (sRNA) antagonist of CsrA, we further explored the relationship between sdiA and the Csr system. Primer extension analysis revealed four putative transcription start sites within 85 nucleotides of the sdiA initiation codon. Potential σ(70)-dependent promoters were identified for each of these primer extension products. In addition, two CsrA binding sites were predicted in the initially translated region of sdiA. Expression of chromosomally integrated sdiA'-'lacZ translational fusions containing the entire promoter and CsrA binding site regions indicates that CsrA represses sdiA expression. The results from gel shift and footprint studies demonstrate that tight binding of CsrA requires both of these sites. Furthermore, the results from toeprint and in vitro translation experiments indicate that CsrA represses translation of sdiA by directly competing with 30S ribosomal subunit binding. Thus, this represents the first example of CsrA preventing translation by interacting solely within the coding region of an mRNA target.

  2. CsrA Represses Translation of sdiA, Which Encodes the N-Acylhomoserine-l-Lactone Receptor of Escherichia coli, by Binding Exclusively within the Coding Region of sdiA mRNA ▿ †

    PubMed Central

    Yakhnin, Helen; Baker, Carol S.; Berezin, Igor; Evangelista, Michael A.; Rassin, Alisa; Romeo, Tony; Babitzke, Paul

    2011-01-01

    The RNA binding protein CsrA is the central component of a conserved global regulatory system that activates or represses gene expression posttranscriptionally. In every known example of CsrA-mediated translational control, CsrA binds to the 5′ untranslated region of target transcripts, thereby repressing translation initiation and/or altering the stability of the RNA. Furthermore, with few exceptions, repression by CsrA involves binding directly to the Shine-Dalgarno sequence and blocking ribosome binding. sdiA encodes the quorum-sensing receptor for N-acyl-l-homoserine lactone in Escherichia coli. Because sdiA indirectly stimulates transcription of csrB, which encodes a small RNA (sRNA) antagonist of CsrA, we further explored the relationship between sdiA and the Csr system. Primer extension analysis revealed four putative transcription start sites within 85 nucleotides of the sdiA initiation codon. Potential σ70-dependent promoters were identified for each of these primer extension products. In addition, two CsrA binding sites were predicted in the initially translated region of sdiA. Expression of chromosomally integrated sdiA′-′lacZ translational fusions containing the entire promoter and CsrA binding site regions indicates that CsrA represses sdiA expression. The results from gel shift and footprint studies demonstrate that tight binding of CsrA requires both of these sites. Furthermore, the results from toeprint and in vitro translation experiments indicate that CsrA represses translation of sdiA by directly competing with 30S ribosomal subunit binding. Thus, this represents the first example of CsrA preventing translation by interacting solely within the coding region of an mRNA target. PMID:21908661

  3. Sensitive Whole-Cell Biosensor Suitable for Detecting a Variety of N-Acyl Homoserine Lactones in Intact Rhizosphere Microbial Communities▿

    PubMed Central

    DeAngelis, Kristen M.; Firestone, Mary K.; Lindow, Steven E.

    2007-01-01

    To investigate quorum sensing in rhizosphere soil, a whole-cell biosensor, Agrobacterium tumefaciens(pAHL-Ice), was constructed. The biosensor responded to all N-acyl homoserine lactones (AHLs) tested, except C4 homoserine lactone, with a minimum detection limit of 10−12 M, as well as to both exogenously added AHLs and AHL-producing bacterial strains in soil. This highly sensitive biosensor reveals for the first time the increased AHL availability in intact rhizosphere microbial communities compared to that in bulk soil. PMID:17400771

  4. Kinetics of the AHL regulatory system in a model biofilm system: how many bacteria constitute a "quorum"?

    PubMed

    Nilsson, P; Olofsson, A; Fagerlind, M; Fagerström, T; Rice, S; Kjelleberg, S; Steinberg, P

    2001-06-08

    Acylated homoserine lactones (AHLs) regulate a wide variety of phenotypes in Gram-negative bacteria. Most research suggests that AHL-mediated phenotypes are not expressed in populations until late logarithmic phase or stationary phase. Here, we model how the concentration of AHLs inside bacterial cells and in a biofilm changes over time as a function of population growth rate, diffusion of AHLs and the rate of autoinduction. Our theoretical results show that the concentration of AHLs inside a single bacterium (and by implication induction of a phenotype) has a non-trivial behaviour over time, and often exhibits a rapid increase early in population growth. This rapid increase is followed by a plateau, followed by another rise in the concentration of AHLs, to a second plateau. High concentrations of AHLs inside the bacterial cell early in population growth are positively affected by slow diffusion rates out of the cell and the biofilm, slow bacterial growth rates and fast autoinduction. In contrast, fast growth rates, slow autoinduction rates and high diffusion rates result in a high concentration plateau in stationary phase. More generally, the density-dependent nature of AHL regulation can be viewed as a trade-off between factors that dilute intracellular concentrations of AHLs (diffusion out of the cell, cell division), and those that increase concentrations (a slowing or restriction of diffusion or growth, or autoinduction). These results suggest that expression of AHL-mediated phenotypes can occur at relatively low cell densities and low external/environmental AHL concentrations. Copyright 2001 Academic Press.

  5. Attenuation of Quorum Sensing Regulated Virulence of Pectobacterium carotovorum subsp. carotovorum through an AHL Lactonase Produced by Lysinibacillus sp. Gs50

    PubMed Central

    Garge, Sneha S.; Nerurkar, Anuradha S.

    2016-01-01

    Quorum sensing (QS) is a mechanism in which Gram negative bacterial pathogens sense their population density through acyl homoserine lactones (AHLs) and regulate the expression of virulence factors. Enzymatic degradation of AHLs by lactonases, known as quorum quenching (QQ), is thus a potential strategy for attenuating QS regulated bacterial infections. We characterised the QQ activity of soil isolate Lysinibacillus sp. Gs50 and explored its potential for controlling bacterial soft rot of crop plants. Lysinibacillus sp. Gs50 inactivated AHL, which could be restored upon acidification, suggested that inactivation was due to the lactone ring hydrolysis of AHL. Heterologous expression of cloned gene for putative hydrolase (792 bp) designated adeH from Lysinibacillus sp. Gs50 produced a ~29 kDa protein which degraded AHLs of varying chain length. Mass spectrometry analysis of AdeH enzymatic reaction product revealed that AdeH hydrolyses the lactone ring of AHL and hence is an AHL lactonase. Multiple sequence alignment of the amino acid sequence of AdeH showed that it belongs to the metallo- β- lactamase superfamily, has a conserved “HXHXDH” motif typical of AHL lactonases. KM for AdeH for C6HSL was found to be 3.089 μM and the specific activity was 0.8 picomol min-1μg-1. AdeH has not so far been reported from any Lysinibacillus sp. and has less than 40% identity with known AHL lactonases. Finally we found that Lysinibacillus sp. Gs50 can degrade AHL produced by Pectobacterium carotovorum subsp. carotovorum (Pcc), a common cause of soft rot. This QQ activity causes a decrease in production of plant cell wall degrading enzymes of Pcc and attenuates symptoms of soft rot in experimental infection of potato, carrot and cucumber. Our results demonstrate the potential of Lysinibacillus sp. Gs50 as a preventive and curative biocontrol agent. PMID:27911925

  6. Production of N-acyl homoserine lactones by the sponge-associated marine actinobacteria Salinispora arenicola and Salinispora pacifica.

    PubMed

    Bose, Utpal; Ortori, Catharine A; Sarmad, Sarir; Barrett, David A; Hewavitharana, Amitha K; Hodson, Mark P; Fuerst, John A; Shaw, P Nicholas; Boden, Rich

    2017-01-01

    The structures of acyl homoserine lactone (AHL) compounds and their quantification were accomplished using an integrated liquid chromatography-mass spectrometry approach. The precursor and product ions, along with retention times of peaks, were searched against an in-house database of AHLs and structures confirmed by accurate mass and by comparison with authentic AHL standards. The two compounds, N-(3-oxodecanoyl)-L-homoserine lactone and N-(3-oxododecanoyl)-L-homoserine lactone, were characterised and quantified in Salinispora sp. cultures. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. N-acyl-homoserine lactone-mediated quorum-sensing in Azospirillum: an exception rather than a rule.

    PubMed

    Vial, Ludovic; Cuny, Caroline; Gluchoff-Fiasson, Katia; Comte, Gilles; Oger, Phil M; Faure, Denis; Dessaux, Yves; Bally, René; Wisniewski-Dyé, Florence

    2006-11-01

    Forty Azospirillum strains were tested for their ability to synthesize N-acyl-homoserine lactones (AHLs). AHL production was detected for four strains belonging to the lipoferum species and isolated from a rice rhizosphere. AHL molecules were structurally identified for two strains: Azospirillum lipoferum TVV3 produces 3O,C(8)-HSL (N-3-oxo-octanoyl-homoserine-lactone), C(8)-HSL (N-3-octanoyl-homoserine-lactone), 3O,C(10)-HSL (N-3-oxo-decanoyl-homoserine-lactone), 3OH,C(10)-HSL (N-3-hydroxy-decanoyl-homoserine-lactone) and C(10)-HSL (N-3-decanoyl-homoserine-lactone), whereas A. lipoferum B518 produced 3O,C(6)-HSL (N-3-oxo-hexanoyl-homoserine-lactone), C(6)-HSL (N-3-hexanoyl-homoserine-lactone), 3O,C(8)-HSL, 3OH,C(8)-HSL and C(8)-HSL. Genes involved in AHL production were characterized for A. lipoferum TVV3 by generating a genomic library and complementing an AHL-deficient strain with sensor capabilities. Those genes, designated alpI and alpR, were found to belong to the luxI and luxR families, respectively. When cloned in a suitable heterologous host, alpI and alpR could direct the synthesis of the five cognate AHLs present in A. lipoferum TVV3. These two adjacent genes were found to be located on a 85 kb plasmid. Southern hybridization experiments with probes alpI/R indicated that genes involved in AHL production in the three other AHL-producing strains were not closely related to alpI and alpR. This study demonstrates that AHL-based quorum-sensing is not widespread among the genus Azospirillum and could be found only in some A. lipoferum strains.

  8. Homoserine Lactones Influence the Reaction of Plants to Rhizobia

    PubMed Central

    Zarkani, Azhar A.; Stein, Elke; Röhrich, Christian R.; Schikora, Marek; Evguenieva-Hackenberg, Elena; Degenkolb, Thomas; Vilcinskas, Andreas; Klug, Gabriele; Kogel, Karl-Heinz; Schikora, Adam

    2013-01-01

    Bacterial quorum sensing molecules not only grant the communication within bacterial communities, but also influence eukaryotic hosts. N-acyl-homoserine lactones (AHLs) produced by pathogenic or beneficial bacteria were shown to induce diverse reactions in animals and plants. In plants, the reaction to AHLs depends on the length of the lipid side chain. Here we investigated the impact of two bacteria on Arabidopsis thaliana, which usually enter a close symbiosis with plants from the Fabaceae (legumes) family and produce a long-chain AHL (Sinorhizobium meliloti) or a short-chain AHL (Rhizobium etli). We demonstrate that, similarly to the reaction to pure AHL molecules, the impact, which the inoculation with rhizosphere bacteria has on plants, depends on the type of the produced AHL. The inoculation with oxo-C14-HSL-producing S. meliloti strains enhanced plant resistance towards pathogenic bacteria, whereas the inoculation with an AttM lactonase-expressing S. meliloti strain did not. Inoculation with the oxo-C8-HSL-producing R. etli had no impact on the resistance, which is in agreement with our previous hypothesis. In addition, plants seem to influence the availability of AHLs in the rhizosphere. Taken together, this report provides new insights in the role of N-acyl-homoserine lactones in the inter-kingdom communication at the root surface. PMID:23965976

  9. gfp-Based N-Acyl Homoserine-Lactone Sensor Systems for Detection of Bacterial Communication

    PubMed Central

    Andersen, Jens Bo; Heydorn, Arne; Hentzer, Morten; Eberl, Leo; Geisenberger, Otto; Christensen, Bjarke Bak; Molin, So/ren; Givskov, Michael

    2001-01-01

    In order to perform single-cell analysis and online studies of N-acyl homoserine lactone (AHL)-mediated communication among bacteria, components of the Vibrio fischeri quorum sensor encoded by luxR-PluxI have been fused to modified versions of gfpmut3∗ genes encoding unstable green fluorescent proteins. Bacterial strains harboring this green fluorescent sensor detected a broad spectrum of AHL molecules and were capable of sensing the presence of 5 nM N-3-oxohexanoyl-l-homoserine lactone in the surroundings. In combination with epifluorescent microscopy, the sensitivity of the sensor enabled AHL detection at the single-cell level and allowed for real-time measurements of fluctuations in AHL concentrations. This green fluorescent AHL sensor provides a state-of-the-art tool for studies of communication between the individuals present in mixed bacterial communities. PMID:11157219

  10. Biofilm activity and sludge characteristics affected by exogenous N-acyl homoserine lactones in biofilm reactors.

    PubMed

    Hu, Huizhi; He, Junguo; Liu, Jian; Yu, Huarong; Zhang, Jie

    2016-07-01

    This study verified the effect of N-acyl homoserine lactone (AHL) concentrations on mature biofilm systems. Three concentrations of an AHL mixture were used in the batch test. Introducing of 5nM AHLs significantly increased biofilm activity and increased sludge characteristics, which resulted in better pollutant removal performance, whereas exogenous 50nM and 500nM AHLs limited pollutant removal, especially COD and nitrogen removal. To further identify how exogenous signal molecular affects biofilm system nitrogen removal, analyzing of nitrifying bacteria through real-time polymerase chain reaction (RT-PCR) revealed that these additional signal molecules affect nitrifying to total bacteria ratio. In addition, the running state of the system was stable during 15days of operation without an AHL dose, which suggests that the changes in the system due to AHL are irreversible. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Stenotrophomonas maltophilia responds to exogenous AHL signals through the LuxR solo SmoR (Smlt1839).

    PubMed

    Martínez, Paula; Huedo, Pol; Martinez-Servat, Sònia; Planell, Raquel; Ferrer-Navarro, Mario; Daura, Xavier; Yero, Daniel; Gibert, Isidre

    2015-01-01

    Quorum Sensing (QS) mediated by Acyl Homoserine Lactone (AHL) molecules are probably the most widespread and studied among Gram-negative bacteria. Canonical AHL systems are composed by a synthase (LuxI family) and a regulator element (LuxR family), whose genes are usually adjacent in the genome. However, incomplete AHL-QS machinery lacking the synthase LuxI is frequently observed in Proteobacteria, and the regulator element is then referred as LuxR solo. It has been shown that certain LuxR solos participate in interspecific communication by detecting signals produced by different organisms. In the case of Stenotrophomonas maltophilia, a preliminary genome sequence analysis revealed numerous putative luxR genes, none of them associated to a luxI gene. From these, the hypothetical LuxR solo Smlt1839, here designated SmoR, presents a conserved AHL binding domain and a helix-turn-helix DNA binding motif. Its genomic organization-adjacent to hchA gene-indicate that SmoR belongs to the new family "LuxR regulator chaperone HchA-associated." AHL-binding assays revealed that SmoR binds to AHLs in-vitro, at least to oxo-C8-homoserine lactone, and it regulates operon transcription, likely by recognizing a conserved palindromic regulatory box in the hchA upstream region. Supplementation with concentrated supernatants from Pseudomonas aeruginosa, which contain significant amounts of AHLs, promoted swarming motility in S. maltophilia. Contrarily, no swarming stimulation was observed when the P. aeruginosa supernatant was treated with the lactonase AiiA from Bacillus subtilis, confirming that AHL contributes to enhance the swarming ability of S. maltophilia. Finally, mutation of smoR resulted in a swarming alteration and an apparent insensitivity to the exogenous AHLs provided by P. aeruginosa. In conclusion, our results demonstrate that S. maltophilia senses AHLs produced by neighboring bacteria through the LuxR solo SmoR, regulating population behaviors such as swarming

  12. Stenotrophomonas maltophilia responds to exogenous AHL signals through the LuxR solo SmoR (Smlt1839)

    PubMed Central

    Martínez, Paula; Huedo, Pol; Martinez-Servat, Sònia; Planell, Raquel; Ferrer-Navarro, Mario; Daura, Xavier; Yero, Daniel; Gibert, Isidre

    2015-01-01

    Quorum Sensing (QS) mediated by Acyl Homoserine Lactone (AHL) molecules are probably the most widespread and studied among Gram-negative bacteria. Canonical AHL systems are composed by a synthase (LuxI family) and a regulator element (LuxR family), whose genes are usually adjacent in the genome. However, incomplete AHL-QS machinery lacking the synthase LuxI is frequently observed in Proteobacteria, and the regulator element is then referred as LuxR solo. It has been shown that certain LuxR solos participate in interspecific communication by detecting signals produced by different organisms. In the case of Stenotrophomonas maltophilia, a preliminary genome sequence analysis revealed numerous putative luxR genes, none of them associated to a luxI gene. From these, the hypothetical LuxR solo Smlt1839, here designated SmoR, presents a conserved AHL binding domain and a helix-turn-helix DNA binding motif. Its genomic organization—adjacent to hchA gene—indicate that SmoR belongs to the new family “LuxR regulator chaperone HchA-associated.” AHL-binding assays revealed that SmoR binds to AHLs in-vitro, at least to oxo-C8-homoserine lactone, and it regulates operon transcription, likely by recognizing a conserved palindromic regulatory box in the hchA upstream region. Supplementation with concentrated supernatants from Pseudomonas aeruginosa, which contain significant amounts of AHLs, promoted swarming motility in S. maltophilia. Contrarily, no swarming stimulation was observed when the P. aeruginosa supernatant was treated with the lactonase AiiA from Bacillus subtilis, confirming that AHL contributes to enhance the swarming ability of S. maltophilia. Finally, mutation of smoR resulted in a swarming alteration and an apparent insensitivity to the exogenous AHLs provided by P. aeruginosa. In conclusion, our results demonstrate that S. maltophilia senses AHLs produced by neighboring bacteria through the LuxR solo SmoR, regulating population behaviors such as swarming

  13. Construction of a dual fluorescence whole-cell biosensor to detect N-acyl homoserine lactones.

    PubMed

    Deng, Xuemei; Zhuang, Guoqiang; Ma, Anzhou; Yu, Qing; Zhuang, Xuliang

    2014-02-01

    Detection of N-acyl homoserine lactones (AHLs) is useful for understanding quorum sensing (QS) behaviors, including biofilm formation, virulence and metabolism. For detecting AHLs and indicating the host cells in situ, we constructed the plasmid pUCGMA2T(1-4) to make a dual fluorescent whole-cell biosensor based on the AhlIR AHL system of Pseudomonas syringae pv. syringae B728a. The plasmid contains three components: constitutively expressed P(npatII::gfp) for indicating host cells, P(ahlI::mcherry) that produces red fluorescence in response to AHL, and the ahlR gene that encodes an AHL regulatory protein. Meanwhile, two copies of T(1-4) (four tandem copies of a transcriptional terminator) were added into the plasmid to reduce background. The results showed that when the plasmid was placed into Escherichia coli, the dual fluorescence whole-cell biosensor was able to respond with red fluorescence within 6 hr to 5 x 10(-8)-1 x 10(-5) mol/L of 3OC6-HSL. Bright green fluorescence indicated the host cells. Furthermore, when the plasmid was transferred to wildtype Pseudomonas PhTA125 (an AHL-producing bacterium), it also showed both green and red fluorescence. This result demonstrates that this plasmid can be used to construct whole-cell indicators that can indicate the AHL response and spatial behaviors of microbes in a microenvironmental niche.

  14. Uptake, degradation and chiral discrimination of N-acyl-D/L-homoserine lactones by barley (Hordeum vulgare) and yam bean (Pachyrhizus erosus) plants.

    PubMed

    Götz, Christine; Fekete, Agnes; Gebefuegi, Istvan; Forczek, Sándor T; Fuksová, Kvetoslava; Li, Xiaojing; Englmann, Matthias; Gryndler, Milan; Hartmann, Anton; Matucha, Miroslav; Schmitt-Kopplin, Philippe; Schröder, Peter

    2007-11-01

    Bacterial intraspecies and interspecies communication in the rhizosphere is mediated by diffusible signal molecules. Many Gram-negative bacteria use N-acyl-homoserine lactones (AHLs) as autoinducers in the quorum sensing response. While bacterial signalling is well described, the fate of AHLs in contact with plants is much less known. Thus, adsorption, uptake and translocation of N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL) and N-decanoyl-homoserine lactone (C10-HSL) were studied in axenic systems with barley (Hordeum vulgare L.) and the legume yam bean (Pachyrhizus erosus (L.) Urban) as model plants using ultra-performance liquid chromatography (UPLC), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tritium-labelled AHLs. Decreases in AHL concentration due to abiotic adsorption or degradation were tolerable under the experimental conditions. The presence of plants enhanced AHL decline in media depending on the compounds' lipophilicity, whereby the legume caused stronger AHL decrease than barley. All tested AHLs were traceable in root extracts of both plants. While all AHLs except C10-HSL were detectable in barley shoots, only C6-HSL was found in shoots of yam bean. Furthermore, tritium-labelled AHLs were used to determine short-term uptake kinetics. Chiral separation by GC-MS revealed that both plants discriminated D-AHL stereoisomers to different extents. These results indicate substantial differences in uptake and degradation of different AHLs in the plants tested.

  15. Modified N-acyl-homoserine lactones as chemical probes for the elucidation of plant-microbe interactions.

    PubMed

    Thomanek, Heike; Schenk, Sebastian T; Stein, Elke; Kogel, Karl-Heinz; Schikora, Adam; Maison, Wolfgang

    2013-09-25

    Gram-negative bacteria often use N-acyl-homoserine lactones (AHLs) as signal molecules to monitor their local population densities and to regulate gene-expression in a process called "Quorum Sensing" (QS). This cell-to-cell communication allows bacteria to adapt to environmental changes and to behave as multicellular communities. QS plays a key role in both bacterial virulence towards the host and symbiotic interactions with other organisms. Plants also perceive AHLs and respond to them with changes in gene expression or modifications in development. Herein, we report the synthesis of new AHL-derivatives for the investigation and identification of AHL-interacting proteins. We show that our new compounds are still recognised by different bacteria and that a novel biotin-tagged-AHL derivative interacts with a bacterial AHL receptor.

  16. Pseudomonas cremoricolorata Strain ND07 Produces N-acyl Homoserine Lactones as Quorum Sensing Molecules

    PubMed Central

    Yunos, Nina Yusrina Muhamad; Tan, Wen-Si; Koh, Chong-Lek; Sam, Choon-Kook; Mohamad, Nur Izzati; Tan, Pui-Wan; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Quorum sensing (QS) is a bacterial cell-to-cell communication system controlling QS-mediated genes which is synchronized with the population density. The regulation of specific gene activity is dependent on the signaling molecules produced, namely N-acyl homoserine lactones (AHLs). We report here the identification and characterization of AHLs produced by bacterial strain ND07 isolated from a Malaysian fresh water sample. Molecular identification showed that strain ND07 is clustered closely to Pseudomonas cremoricolorata. Spent culture supernatant extract of P. cremoricolorata strain ND07 activated the AHL biosensor Chromobacterium violaceum CV026. Using high resolution triple quadrupole liquid chromatography-mass spectrometry, it was confirmed that P. cremoricolorata strain ND07 produced N-octanoyl-l-homoserine lactone (C8-HSL) and N-decanoyl-l-homoserine lactone (C10-HSL). To the best of our knowledge, this is the first documentation on the production of C10-HSL in P. cremoricolorata strain ND07. PMID:24984061

  17. Proteomic assessment of the role of N-acyl homoserine lactone in Shewanella putrefaciens spoilage.

    PubMed

    Zhang, Caili; Zhu, Suqin; Jatt, Abdul-Nabi; Pan, Yurong; Zeng, Mingyong

    2017-08-21

    Shewanella spp. are the common spoilage organisms found in aquatic food products stored at low temperature and their spoilage mechanism has been reported to be mediated by quorum sensing (QS). However, the specifically expressed proteins responding to N-acyl homoserine-lactone (AHLs) were seldom reported. The present study aims to evaluate the effects of different AHL signal molecules on Shewanella putrefaciens Z4 isolated from refrigerated turbot (Scophthalmus maximus) at the proteome level. The results revealed that exogenous AHLs were utilized as QS signal molecules by S. putrefaciens Z4, and AHLs were not degraded by intracellular or extracellular enzymes secreted by S. putrefaciens Z4. Twenty-three differently expressed spots upon the addition of AHLs were selected and identified by liquid chromatography-mass spectrometry (LC-MS). The results indicated that proteins involving in growth and metabolism (i.e., citrate synthase, succinate semialdehyde dehydrogenase), environment adaptation and regulators (i.e., polysaccharide deacetylases, transaldolase) were down-regulated upon three kinds of AHLs (C4-HSL, C6-HSL, and O-C6-HSL), whereas the abundance of stress response protein and DNA ligase were elevated by the addition of exogenous AHLs. Moreover, the effects of exogenous C6-HSL and O-C6-HSLwere prominent. These results provide evidence that AHL-based QS signal molecules affected some important metabolic properties of S. putrefaciens. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  18. Discovery of Pantoea rodasii Strain ND03 that Produces N-(3-Oxo-hexanoyl)-l-homoserine Lactone

    PubMed Central

    Yunos, Nina Yusrina Muhamad; Tan, Wen-Si; Mohamad, Nur Izzati; Tan, Pui-Wan; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Proteobacteria use quorum sensing to regulate target gene expression in response to population density. Quorum sensing (QS) is achieved via so-called signalling molecules and the best-studied QS signalling system uses N-acyl homoserine lactones (AHLs). This study aimed to identify and characterize the production of AHLs by a bacterium ND03 isolated from a Malaysian tropical rainforest waterfall. Molecular identification showed that ND03 is a Pantoea sp. closely related to Pantoea rodasii. We used Chromobacterium violaceum CV026, an AHL biosensor for preliminary AHL production screening and then used high resolution triple quadrupole liquid chromatography-mass spectrometry, to confirm that P. rodasii strain ND03 produced N-(3-oxo-hexanoyl)-l-homoserine lactone (3-oxo-C6-HSL). To the best of our knowledge, this is the first report for such a discovery in P. rodasii strain ND03. PMID:24859023

  19. Discovery of Pantoea rodasii strain ND03 that produces N-(3-Oxo-hexanoyl)-L-homoserine lactone.

    PubMed

    Yunos, Nina Yusrina Muhamad; Tan, Wen-Si; Mohamad, Nur Izzati; Tan, Pui-Wan; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-05-23

    Proteobacteria use quorum sensing to regulate target gene expression in response to population density. Quorum sensing (QS) is achieved via so-called signalling molecules and the best-studied QS signalling system uses N-acyl homoserine lactones (AHLs). This study aimed to identify and characterize the production of AHLs by a bacterium ND03 isolated from a Malaysian tropical rainforest waterfall. Molecular identification showed that ND03 is a Pantoea sp. closely related to Pantoea rodasii. We used Chromobacterium violaceum CV026, an AHL biosensor for preliminary AHL production screening and then used high resolution triple quadrupole liquid chromatography-mass spectrometry, to confirm that P. rodasii strain ND03 produced N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL). To the best of our knowledge, this is the first report for such a discovery in P. rodasii strain ND03.

  20. Plants secrete substances that mimic bacterial N-acyl homoserine lactone signal activities and affect population density-dependent behaviors in associated bacteria.

    PubMed

    Teplitski, M; Robinson, J B; Bauer, W D

    2000-06-01

    In gram-negative bacteria, many important changes in gene expression and behavior are regulated in a population density-dependent fashion by N-acyl homoserine lactone (AHL) signal molecules. Exudates from pea (Pisum sativum) seedlings were found to contain several separable activities that mimicked AHL signals in well-characterized bacterial reporter strains, stimulating AHL-regulated behaviors in some strains while inhibiting such behaviors in others. The chemical nature of the active mimic compounds is currently unknown, but all extracted differently into organic solvents than common bacterial AHLs. Various species of higher plants in addition to pea were found to secrete AHL mimic activities. The AHL signal-mimic compounds could prove to be important in determining the outcome of interactions between higher plants and a diversity of pathogenic, symbiotic, and saprophytic bacteria.

  1. [Synthesis of signaling N-acyl-homoserine-lactones participating in quorum sensing in rhizosphere and soil bacteria Pseudomonas and Xanthomonas].

    PubMed

    Khmel', I A; Veselova, M A; Metlitskaia, A Z; Klein, S; Lipasova, V A; Maiatskaia, A V; Chernin, L S

    2002-04-01

    Signaling molecules assigned to N-acyl-homoserine-lactones (AHL) serve as autoinducers for the genes controlling the quorum sensing regulatory system. In many gram-negative bacteria, AHL are the key factors responsible for density-dependent regulation of exoenzyme and secondary metabolite production; they also participate in interaction between bacteria and higher organisms. The soil and rhisosphere bacteria Pseudomonas and Xanthomonas from different geographical zones of Russia and the former USSR were analyzed for the presence of the AHL producers. Screening was conducted by using a test system based on the mutant strain Chromobacterium violaceum, which was unable to synthesize AHL but produced a pigment violacein in the presence of exogenous AHL. The AHL-like compounds proved to be formed by 9.7% of the studied bacteria. Various Pseudomonas species differed in the capacity to synthesize this compounds. In at least a half of the isolated P. aureofaciens and P. aeruginosa, an intense AHL production was observed, whereas the AHL-producers were far less frequent among the P. fluorescens, P. chlororaphis, P. lemonnieri, P. geniculata, and P. putida. None of the 41 Xanthomonas maltophilia strains examined synthesized AHL.

  2. Exogenous N-acyl-homoserine lactones enhance the expression of flagella of Pseudomonas syringae and activate defence responses in plants.

    PubMed

    Cheng, Feifei; Ma, Anzhou; Zhuang, Guoqiang; Fray, Rupert G

    2016-10-18

    In order to cope with pathogens, plants have evolved sophisticated mechanisms to sense pathogenic attacks and to induce defence responses. The N-acyl-homoserine lactone (AHL)-mediated quorum sensing in bacteria regulates diverse physiological processes, including those involved in pathogenicity. In this work, we study the interactions between AHL-producing transgenic tobacco plants and Pseudomonas syringae pv. tabaci 11528 (P. syringae 11528). Both a reduced incidence of disease and decrease in the growth of P. syringae 11528 were observed in AHL-producing plants compared with wild-type plants. The present data indicate that plant-produced AHLs enhance disease resistance against this pathogen. Subsequent RNA-sequencing analysis showed that the exogenous addition of AHLs up-regulated the expression of P. syringae 11528 genes for flagella production. Expression levels of plant defence genes in AHL-producing and wild-type plants were determined by quantitative real-time polymerase chain reaction. These data showed that plant-produced AHLs activated a wide spectrum of defence responses in plants following inoculation, including the oxidative burst, hypersensitive response, cell wall strengthening, and the production of certain metabolites. These results demonstrate that exogenous AHLs alter the gene expression patterns of pathogens, and plant-produced AHLs either directly or indirectly enhance plant local immunity during the early stage of plant infection.

  3. Thiourea-Catalyzed Aminolysis of N-acyl Homoserine Lactones

    DTIC Science & Technology

    2013-01-01

    of N-acyl homoserine lactones (AHLs), molecules integral to bacterial quorum sensing . The catalysts afford rate enhancement of up to 10 times the...SUBJECT TERMS quorum sensing Michael A. Bertucci, Stephen J. Lee, Michel R. Gagné University of North Carolina - Chapel Hill Office of Sponsored... quorum sensing . The catalysts afford rate enhancement of up to 10 times the control in CD3CN. Mild catalysis in other polar aprotic solvents is

  4. N-Acyl Homoserine Lactone Production by Klebsiella pneumoniae Isolated from Human Tongue Surface

    PubMed Central

    Yin, Wai-Fong; Purmal, Kathiravan; Chin, Shenyang; Chan, Xin-Yue; Koh, Chong-Lek; Sam, Choon-Kook; Chan, Kok-Gan

    2012-01-01

    Bacteria communicate by producing quorum sensing molecules called autoinducers, which include autoinducer-1, an N-hexanoyl homoserine lactone (AHL), and autoinducer-2. Bacteria present in the human oral cavity have been shown to produce autoinducer-2, but not AHL. Here, we report the isolation of two AHL-producing Klebsiella pneumoniae strains from the posterior dorsal surface of the tongue of a healthy individual. Spent culture supernatant extracts from K. pneumoniae activated the biosensors Agrobacterium tumefaciens NTL4(pZLR4) and Escherichia coli [pSB401], suggesting the presence of both long and short chain AHLs. High resolution mass spectrometry analyses of these extracts confirmed that both K. pneumoniae isolates produced N-octanoylhomoserine lactone and N-3-dodecanoyl-l-homoserine lactone. To the best of our knowledge, this is the first report of the isolation of K. pneumoniae from the posterior dorsal surface of the human tongue and the production of these AHLs by this bacterium. PMID:22737019

  5. High-performance liquid chromatography analysis of N-acyl homoserine lactone hydrolysis by paraoxonases.

    PubMed

    Teiber, John F; Draganov, Dragomir I

    2011-01-01

    Mammalian paraoxonases (PONs) are a unique, highly conserved family of calcium-dependent esterases consisting of PON1, PON2, and PON3. The PONs can hydrolyze the lactone ring of a range of N-acyl-L: -homoserine lactone (AHL) quorum sensing signaling molecules, rendering them inactive. This chapter describes a method that utilizes high-performance liquid chromatography analysis with UV detection for determining the rate of AHL hydrolysis in cell lysates, tissue homogenates, serum, and with purified proteins. Also described are the techniques used to prepare cell culture lysates and tissue homogenates for analysis and the use of class-specific enzyme inhibitors to determine the contribution of PONs to AHL hydrolysis in the samples.

  6. A Sinorhizobium meliloti-specific N-acyl homoserine lactone quorum-sensing signal increases nodule numbers in Medicago truncatula independent of autoregulation.

    PubMed

    Veliz-Vallejos, Debora F; van Noorden, Giel E; Yuan, Mengqi; Mathesius, Ulrike

    2014-01-01

    N-acyl homoserine lactones (AHLs) act as quorum sensing signals that regulate cell-density dependent behaviors in many gram-negative bacteria, in particular those important for plant-microbe interactions. AHLs can also be recognized by plants, and this may influence their interactions with bacteria. Here we tested whether the exposure to AHLs affects the nodule-forming symbiosis between legume hosts and rhizobia. We treated roots of the model legume, Medicago truncatula, with a range of AHLs either from its specific symbiont, Sinorhizobium meliloti, or from the potential pathogens, Pseudomonas aeruginosa and Agrobacterium vitis. We found increased numbers of nodules formed on root systems treated with the S. meliloti-specific AHL, 3-oxo-C14-homoserine lactone, at a concentration of 1 μM, while the other AHLs did not result in significant changes to nodule numbers. We did not find any evidence for altered nodule invasion by the rhizobia. Quantification of flavonoids that could act as nod gene inducers in S. meliloti did not show any correlation with increased nodule numbers. The effects of AHLs were specific for an increase in nodule numbers, but not lateral root numbers or root length. Increased nodule numbers following 3-oxo-C14-homoserine lactone treatment were under control of autoregulation of nodulation and were still observed in the autoregulation mutant, sunn4 (super numeric nodules4). However, increases in nodule numbers by 3-oxo-C14-homoserine lactone were not found in the ethylene-insensitive sickle mutant. A comparison between M. truncatula with M. sativa (alfalfa) and Trifolium repens (white clover) showed that the observed effects of AHLs on nodule numbers were specific to M. truncatula, despite M. sativa nodulating with the same symbiont. We conclude that plant perception of the S. meliloti-specific 3-oxo-C14-homoserine lactone influences nodule numbers in M. truncatula via an ethylene-dependent, but autoregulation-independent mechanism.

  7. Quorum quenching by an N-acyl-homoserine lactone acylase from Pseudomonas aeruginosa PAO1.

    PubMed

    Sio, Charles F; Otten, Linda G; Cool, Robbert H; Diggle, Stephen P; Braun, Peter G; Bos, Rein; Daykin, Mavis; Cámara, Miguel; Williams, Paul; Quax, Wim J

    2006-03-01

    The virulence of the opportunistic human pathogen Pseudomonas aeruginosa PAO1 is controlled by an N-acyl-homoserine lactone (AHL)-dependent quorum-sensing system. During functional analysis of putative acylase genes in the P. aeruginosa PAO1 genome, the PA2385 gene was found to encode an acylase that removes the fatty acid side chain from the homoserine lactone (HSL) nucleus of AHL-dependent quorum-sensing signal molecules. Analysis showed that the posttranslational processing of the acylase and the hydrolysis reaction type are similar to those of the beta-lactam acylases, strongly suggesting that the PA2385 protein is a member of the N-terminal nucleophile hydrolase superfamily. In a bioassay, the purified acylase was shown to degrade AHLs with side chains ranging in length from 11 to 14 carbons at physiologically relevant low concentrations. The substituent at the 3' position of the side chain did not affect activity, indicating broad-range AHL quorum-quenching activity. Of the two main AHL signal molecules of P. aeruginosa PAO1, N-butanoyl-l-homoserine lactone (C4-HSL) and N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL), only 3-oxo-C12-HSL is degraded by the enzyme. Addition of the purified protein to P. aeruginosa PAO1 cultures completely inhibited accumulation of 3-oxo-C12-HSL and production of the signal molecule 2-heptyl-3-hydroxy-4(1H)-quinolone and reduced production of the virulence factors elastase and pyocyanin. Similar results were obtained when the PA2385 gene was overexpressed in P. aeruginosa. These results demonstrate that the protein has in situ quorum-quenching activity. The quorum-quenching AHL acylase may enable P. aeruginosa PAO1 to modulate its own quorum-sensing-dependent pathogenic potential and, moreover, offers possibilities for novel antipseudomonal therapies.

  8. Quorum Quenching by an N-Acyl-Homoserine Lactone Acylase from Pseudomonas aeruginosa PAO1

    PubMed Central

    Sio, Charles F.; Otten, Linda G.; Cool, Robbert H.; Diggle, Stephen P.; Braun, Peter G.; Bos, Rein; Daykin, Mavis; Cámara, Miguel; Williams, Paul; Quax, Wim J.

    2006-01-01

    The virulence of the opportunistic human pathogen Pseudomonas aeruginosa PAO1 is controlled by an N-acyl-homoserine lactone (AHL)-dependent quorum-sensing system. During functional analysis of putative acylase genes in the P. aeruginosa PAO1 genome, the PA2385 gene was found to encode an acylase that removes the fatty acid side chain from the homoserine lactone (HSL) nucleus of AHL-dependent quorum-sensing signal molecules. Analysis showed that the posttranslational processing of the acylase and the hydrolysis reaction type are similar to those of the beta-lactam acylases, strongly suggesting that the PA2385 protein is a member of the N-terminal nucleophile hydrolase superfamily. In a bioassay, the purified acylase was shown to degrade AHLs with side chains ranging in length from 11 to 14 carbons at physiologically relevant low concentrations. The substituent at the 3′ position of the side chain did not affect activity, indicating broad-range AHL quorum-quenching activity. Of the two main AHL signal molecules of P. aeruginosa PAO1, N-butanoyl-l-homoserine lactone (C4-HSL) and N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL), only 3-oxo-C12-HSL is degraded by the enzyme. Addition of the purified protein to P. aeruginosa PAO1 cultures completely inhibited accumulation of 3-oxo-C12-HSL and production of the signal molecule 2-heptyl-3-hydroxy-4(1H)-quinolone and reduced production of the virulence factors elastase and pyocyanin. Similar results were obtained when the PA2385 gene was overexpressed in P. aeruginosa. These results demonstrate that the protein has in situ quorum-quenching activity. The quorum-quenching AHL acylase may enable P. aeruginosa PAO1 to modulate its own quorum-sensing-dependent pathogenic potential and, moreover, offers possibilities for novel antipseudomonal therapies. PMID:16495538

  9. The AHL- and BDSF-Dependent Quorum Sensing Systems Control Specific and Overlapping Sets of Genes in Burkholderia cenocepacia H111

    PubMed Central

    Aguilar, Claudio; Carlier, Aurelien L.; Grunau, Alexander; Omasits, Ulrich; Zhang, Lian-Hui; Ahrens, Christian H.; Eberl, Leo

    2012-01-01

    Quorum sensing in Burkholderia cenocepacia H111 involves two signalling systems that depend on different signal molecules, namely N-acyl homoserine lactones (AHLs) and the diffusible signal factor cis-2-dodecenoic acid (BDSF). Previous studies have shown that AHLs and BDSF control similar phenotypic traits, including biofilm formation, proteolytic activity and pathogenicity. In this study we mapped the BDSF stimulon by RNA-Seq and shotgun proteomics analysis. We demonstrate that a set of the identified BDSF-regulated genes or proteins are also controlled by AHLs, suggesting that the two regulons partially overlap. The detailed analysis of two mutually regulated operons, one encoding three lectins and the other one encoding the large surface protein BapA and its type I secretion machinery, revealed that both AHLs and BDSF are required for full expression, suggesting that the two signalling systems operate in parallel. In accordance with this, we show that both AHLs and BDSF are required for biofilm formation and protease production. PMID:23185499

  10. Beneficial effects of bacteria-plant communication based on quorum sensing molecules of the N-acyl homoserine lactone group.

    PubMed

    Schikora, Adam; Schenk, Sebastian T; Hartmann, Anton

    2016-04-01

    Bacterial quorum sensing (QS) mechanisms play a crucial role in the proper performance and ecological fitness of bacterial populations. Many key physiological processes are regulated in a QS-dependent manner by auto-inducers, like the N-acyl homoserine lactones (AHLs) in numerous Gram-negative bacteria. In addition, also the interaction between bacteria and eukaryotic hosts can be regulated by AHLs. Those mechanisms gained much attention, because of the positive effects of different AHL molecules on plants. This positive impact ranges from growth promotion to induced resistance and is quite contrasting to the rather negative effects observed in the interactions between bacterial AHL molecules and animals. Only very recently, we began to understand the molecular mechanisms underpinning plant responses to AHL molecules. In this review, we gathered the latest information in this research field. The first part gives an overview of the bacterial aspects of quorum sensing. Later we focus on the impact of AHLs on plant growth and AHL-priming, as one of the most understood phenomena in respect to the inter-kingdom interactions based on AHL-quorum sensing molecules. Finally, we discuss the potential benefits of the understanding of bacteria-plant interaction for the future agricultural applications.

  11. Diversity and N-acyl-homoserine lactone production by Gammaproteobacteria associated with Avicennia marina rhizosphere of South Indian mangroves.

    PubMed

    Viswanath, Ganga; Jegan, Sekar; Baskaran, Viswanathan; Kathiravan, Raju; Prabavathy, Vaiyapuri Ramalingam

    2015-07-01

    The diversity of N-acyl-homoserine lactone (AHL)-producing rhizosphere bacterial community associated with Avicennia marina in the mangrove ecosystems of South India was investigated. Approximately 800 rhizobacteria were isolated from A. marina, and they were screened for the production of AHL using two biosensors, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens NTL4 (pZLR4). Among the total isolates screened, 7% of the rhizobacteria showed positive induction for AHL signals. The BOX-PCR profile of 56 positive isolates represented 11 distinct genotypic groups. Phylogenetic analyses of the 16S rRNA sequences of 16 representatives showed that the isolates belonged to the class Gammaproteobacteria, which represented six different genera: Pseudomonas, Aeromonas, Vibrio, Photobacterium, Serratia and Halomonas. The study also identified three AHL-producing species, namely, Photobacterium halotolerans MSSRF QS48, Vibrio xiamenensis MSSRF QS47 and Pseudomonas sp. MSSRF QS1 that had not been reported previously. AHL profiling by TLC detected short chains C4, C6 and C8-HSL, and long chains C10 and C12-HSL with both unsubstituted and substituted side chains among the 16 representative AHL positives. This is the first report concerning the diversity of AHL-producing Gammaproteobacteria from mangrove ecosystems exhibiting diverse AHL profiles.

  12. Elevated Temperature Enhances Short to Medium Chain Acyl Homoserine Lactone Production by Black Band Disease Associated Vibrios.

    PubMed

    Bhedi, Chinmayee D; Prevatte, Carson W; Lookadoo, Maggie S; Waikel, Patricia A; Gillevet, Patrick M; Sikaroodi, Masoumeh; Campagna, Shawn R; Richardson, Laurie L

    2017-01-29

    Black band disease (BBD) of corals is a horizontally migrating, pathogenic, polymicrobial mat community which is active above a temperature threshold of 27.5°C on the reef. Bacterial isolates from BBD, the surface mucopolysaccharide layer (SML) of healthy corals, and SML of healthy areas of BBD infected corals were tested for production of short to medium chain acyl homoserine lactones (AHLs) using the Chromobacterium violaceum CV026 reporter strain. Of 110 bacterial isolates tested, 19 produced AHLs and 15 of these were from BBD. Eight AHLs were identified using LC-MS/MS, with 3OHC4 the most commonly produced, followed by C6. AHL-producing isolates exposed to three temperatures (24°, 27°, 30°C) revealed that production of three AHLs (3OHC4, 3OHC5, and 3OHC6) significantly increased at 30°C when compared to 24°C. 16S rRNA gene sequencing revealed that all of the AHL producing BBD isolates were vibrios. Metagenomic data of BBD communities showed the presence of AHL (and autoinducer-2) genes, many of which are known to be associated with vibrios. These findings suggest that quorum sensing may be involved in BBD pathobiology and community structure due to enhanced production of quorum sensing signal molecules (AHLs) above the temperature threshold of this globally distributed coral disease.

  13. QsdH, a Novel AHL Lactonase in the RND-Type Inner Membrane of Marine Pseudoalteromonas byunsanensis Strain 1A01261

    PubMed Central

    Huang, Wei; Lin, Yongjun; Yi, Shuyuan; Liu, Pengfu; Shen, Jie; Shao, Zongze; Liu, Ziduo

    2012-01-01

    N-acyl-homoserine lactones (AHLs) are the main quorum-sensing (QS) signals in gram-negative bacteria. AHLs trigger the expression of genes for particular biological functions when their density reaches a threshold. In this study, we identified and cloned the qsdH gene by screening a genomic library of Pseudoalteromonas byunsanensis strain 1A01261, which has AHL-degrading activity. The qsdH gene encoded a GDSL hydrolase found to be located in the N-terminus of a multidrug efflux transporter protein of the resistance-nodulation-cell division (RND) family. We further confirmed that the GDSL hydrolase, QsdH, exhibited similar AHL-degrading activity to the full-length ORF protein. QsdH was expressed and purified to process the N-terminal signal peptide yielding a 27-kDa mature protein. QsdH was capable of inactivating AHLs with an acyl chain ranging from C4 to C14 with or without 3-oxo substitution. High-performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS) analyses showed that QsdH functioned as an AHL lactonase to hydrolyze the ester bond of the homoserine lactone ring of AHLs. In addition, site-directed mutagenesis demonstrated that QsdH contained oxyanion holes (Ser-Gly-Asn) in conserved blocks (I, II, and III), which had important roles in its AHL-degrading activity. Furthermore, the lactonase activity of QsdH was slightly promoted by several divalent ions. Using in silico prediction, we concluded that QsdH was located at the first periplasmic loop of the multidrug efflux transporter protein, which is essential to substrate selectivity for these efflux pumps. These findings led us to assume that the QsdH lactonase and C-terminal efflux pump might be effective in quenching QS of the P. byunsanensis strain 1A01261. Moreover, it was observed that recombinant Escherichia coli producing QsdH proteins attenuated the plant pathogenicity of Erwinia carotovora, which might have potential to control of gram-negative pathogenic

  14. Production of acylated homoserine lactone by gram-positive bacteria isolated from marine water.

    PubMed

    Biswa, Pramal; Doble, Mukesh

    2013-06-01

    Acylated homoserine lactone (AHL)-based quorum sensing (QS) has been reported to be present only in Gram-negative microorganisms. Isolation of a novel Gram-positive microorganism from sea water, capable of producing AHL, is reported here. The isolate (GenBank: JF915892, designated as MPO) belonging to the Exiguobacterium genera is capable of inducing the AHL bioreporters, namely Chromobacterium violaceum CV026, Agrobacterium tumefaceins A136, and E. coli JM 109(psb1075). This inducer is characterized as C3-oxo-octanoyl homoserine lactone (OOHL), and its production reaches a maximum of 15.6 μg L(-1), during the stationary growth phase of the organism. MPO extract when exogenously added inhibits the formation of biofilm for the same organism and lowers the extracellular polymeric substances, indicating an AHL-associated phenotypic trait. The isolated sequence of a probable LuxR homolog from MPO (designated as ExgR) shows similar functional domains and contains conserved residues in LuxR from other known bacterial QS LuxR regulators. Also present immediately downstream to ExgR was found a sequence showing homology to known LuxI synthase of Pseudomonas putida. qPCR analysis suggests an increment in exgR mRNA on addition of AHL, further proving the role of ExgR as a QS regulator.

  15. The molecular structure and catalytic mechanism of a quorum-quenching N-acyl-L-homoserine lactone hydrolase.

    PubMed

    Kim, Myung Hee; Choi, Won-Chan; Kang, Hye Ok; Lee, Jong Suk; Kang, Beom Sik; Kim, Kyung-Jin; Derewenda, Zygmunt S; Oh, Tae-Kwang; Lee, Choong Hwan; Lee, Jung-Kee

    2005-12-06

    In many Gram-negative bacteria, including a number of pathogens such as Pseudomonas aeruginosa and Erwinia carotovora, virulence factor production and biofilm formation are linked to the quorum-sensing systems that use diffusible N-acyl-L-homoserine lactones (AHLs) as intercellular messenger molecules. A number of organisms also contain genes coding for lactonases that hydrolyze AHLs into inactive products, thereby blocking the quorum-sensing systems. Consequently, these enzymes attract intense interest for the development of antiinfection therapies. However, the catalytic mechanism of AHL-lactonase is poorly understood and subject to controversy. We here report a 2.0-angstroms resolution structure of the AHL-lactonase from Bacillus thuringiensis and a 1.7-angstroms crystal structure of its complex with L-homoserine lactone. Despite limited sequence similarity, the enzyme shows remarkable structural similarities to glyoxalase II and RNase Z proteins, members of the metallo-beta-lactamase superfamily. We present experimental evidence that AHL-lactonase is a metalloenzyme containing two zinc ions involved in catalysis, and we propose a catalytic mechanism for bacterial metallo-AHL-lactonases.

  16. [Isolation and identification of Rhodosporidium toruloides R1 degrading N-acyl homoserine lactone].

    PubMed

    Qiu, Jian; Jia, Zhen-hua; Ma, Hong; Zhang, Xia; Song, Shui-shan

    2007-04-01

    In the present study, a AHL-utilizing strain RI was isolated and identified as the genus Rhodosporidium toruloides R1 by physi-biochemical approaches and 18S rDNA sequence analysis, and this strain was designated as R. toruloides R1. Results showed that R. toruloides R1 exhibited the ability to utilize and degrade the all N-acyl homoserine lactones tested in this study. Coculture of R. toruloides R1 with Erwinia carotovora subsp. Carotovora effectively inhibit the soft rot disease of patato caused by E. carotovora. To the best of our knowledge, this is the first report on AHL-degradation of yeast cells.

  17. The Pseudomonas aeruginosa quorum sensing signal molecule N-(3-oxododecanoyl) homoserine lactone enhances keratinocyte migration and induces Mmp13 gene expression in vitro

    SciTech Connect

    Paes, Camila

    2012-10-19

    Highlights: Black-Right-Pointing-Pointer An evidence of the positive effect of AHL on epithelialization process is provided. Black-Right-Pointing-Pointer AHL enhances keratinocyte's ability to migrate in an in vitro scratch wound model. Black-Right-Pointing-Pointer AHL induces the expression of Mmp13. Black-Right-Pointing-Pointer Topical application of AHL represents a possible strategy to treat chronic wounds. -- Abstract: Re-epithelialization is an essential step of wound healing involving three overlapping keratinocyte functions: migration, proliferation and differentiation. While quorum sensing (QS) is a cell density-dependent signaling system that enables bacteria to regulate the expression of certain genes, the QS molecule N-(3-oxododecanoyl) homoserine lactone (AHL) exerts effects also on mammalian cells in a process called inter-kingdom signaling. Recent studies have shown that AHL improves epithelialization in in vivo wound healing models but detailed understanding of the molecular and cellular mechanisms are needed. The present study focused on the AHL as a candidate reagent to improve wound healing through direct modulation of keratinocyte's activity in the re-epithelialization process. Results indicated that AHL enhances the keratinocyte's ability to migrate in an in vitro scratch wound healing model probably due to the high Mmp13 gene expression analysis after AHL treatment that was revealed by real-time RT-PCR. Inhibition of activator protein 1 (AP-1) signaling pathway completely prevented the migration of keratinocytes, and also resulted in a diminished Mmp13 gene expression, suggesting that AP-1 might be essential in the AHL-induced migration. Taken together, these results imply that AHL is a promising candidate molecule to improve re-epithelialization through the induction of migration of keratinocytes. Further investigation is needed to clarify the mechanism of action and molecular pathway of AHL on the keratinocyte migration process.

  18. Possible Quorum Sensing in Marine Snow Bacteria: Production of Acylated Homoserine Lactones by Roseobacter Strains Isolated from Marine Snow

    PubMed Central

    Gram, Lone; Grossart, Hans-Peter; Schlingloff, Andrea; Kiørboe, Thomas

    2002-01-01

    We report here, for the first time, that bacteria associated with marine snow produce communication signals involved in quorum sensing in gram-negative bacteria. Four of 43 marine microorganisms isolated from marine snow were found to produce acylated homoserine lactones (AHLs) in well diffusion and thin-layer chromatographic assays based on the Agrobacterium tumefaciens reporter system. Three of the AHL-producing strains were identified by 16S ribosomal DNA gene sequence analysis as Roseobacter spp., and this is the first report of AHL production by these α-Proteobacteria. It is likely that AHLs in Roseobacter species and other marine snow bacteria govern phenotypic traits (biofilm formation, exoenzyme production, and antibiotic production) which are required mainly when the population reaches high densities, e.g., in the marine snow community. PMID:12147515

  19. N-acyl-homoserine lactones from Enterobacter sakazakii (Cronobacter spp.) and their degradation by Bacillus cereus enzymes.

    PubMed

    Araújo, Francisca Diana da Silva; Esper, Luciana Maria Ramires; Kuaye, Arnaldo Yoshiteru; Sircili, Marcelo Palma; Marsaioli, Anita Jocelyne

    2012-01-18

    A chemical study of acyl-homoserine lactones (acyl-HSLs) produced by Enterobacter sakazakii resulted in the identification of three molecules: (S)-N-heptanoyl-HSL, (S)-N-dodecanoyl-HSL and (S)-N-tetradecanoyl-HSL. Mixed cultures of E. sakazakii and Bacillus cereus depleted E. sakazakii acyl-HSLs, suggesting acyl-HSL degradation by B. cereus hydrolases (hydrolysis of the lactone or amide moiety). The expression of B. cereus acyl-HSL lactonase and acyl-homoserine acylase was confirmed by monitoring the biotransformation of (S)-N-dodecanoyl-HSL into (S)-N-dodecanoyl-homoserine, dodecanoic acid and homoserine in the presence of B. cereus whole cells, using electrospray-mass spectrometry (ESI-MS).

  20. Rice and bean AHL-mimic quorum-sensing signals specifically interfere with the capacity to form biofilms by plant-associated bacteria.

    PubMed

    Pérez-Montaño, Francisco; Jiménez-Guerrero, Irene; Contreras Sánchez-Matamoros, Rocío; López-Baena, Francisco Javier; Ollero, Francisco Javier; Rodríguez-Carvajal, Miguel A; Bellogín, Ramón A; Espuny, M Rosario

    2013-09-01

    Many bacteria regulate their gene expression in response to changes in their population density in a process called quorum sensing (QS), which involves communication between cells mediated by small diffusible signal molecules termed autoinducers. n-acyl-homoserine-lactones (AHLs) are the most common autoinducers in proteobacteria. QS-regulated genes are involved in complex interactions between bacteria of the same or different species and even with some eukaryotic organisms. Eukaryotes, including plants, can interfere with bacterial QS systems by synthesizing molecules that interfere with bacterial QS systems. In this work, the presence of AHL-mimic QS molecules in diverse Oryza sativa (rice) and Phaseolus vulgaris (bean) plant-samples were detected employing three biosensor strains. A more intensive analysis using biosensors carrying the lactonase enzyme showed that bean and rice seed-extract contain molecules that lack the typical lactone ring of AHLs. Interestingly, these molecules specifically alter the QS-regulated biofilm formation of two plant-associated bacteria, Sinorhizobium fredii SMH12 and Pantoea ananatis AMG501, suggesting that plants are able to enhance or to inhibit the bacterial QS systems depending on the bacterial strain. Further studies would contribute to a better understanding of plant-bacteria relationships at the molecular level.

  1. Diverse profiles of N-acyl-homoserine lactone molecules found in cnidarians.

    PubMed

    Ransome, Emma; Munn, Colin B; Halliday, Nigel; Cámara, Miguel; Tait, Karen

    2014-02-01

    Many marine habitats, such as the surface and tissues of marine invertebrates, including corals, harbour diverse populations of microorganisms, which are thought to play a role in the health of their hosts and influence mutualistic and competitive interactions. Investigating the presence and stability of quorum sensing (QS) in these ecosystems may shed light on the roles and control of these bacterial communities. Samples of 13 cnidarian species were screened for the presence and diversity of N-acyl-homoserine lactones (AHLs; a prevalent type of QS molecule) using thin-layer chromatography and an Agrobacterium tumefaciens NTL4 biosensor. Ten of 13 were found to harbour species-specific, conserved AHL profiles. AHLs were confirmed in Anemonia viridis using liquid chromatography tandem mass spectrometry. To assess temporal role and stability, AHLs were investigated in A. viridis from intertidal pools over 16 h. Patterns of AHLs showed conserved profiles except for two mid-chain length AHLs, which increased significantly over the day, peaking at 20:00, but had no correlation with pool chemistry. Denaturing gel electrophoresis of RT-PCR-amplified bacterial 16S rRNA showed the presence of an active bacterial community that changed in composition alongside AHL profiles and contained a number of bands that affiliate with known AHL-producing bacteria. Investigations into the quorum sensing-controlled, species-specific roles of these bacterial communities and how these regulatory circuits are influenced by the coral host and members of the bacterial community are imperative to expand our knowledge of these interactions with respect to the maintenance of coral health. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  2. Detection of Diverse N-Acyl-Homoserine Lactones in Vibrio alginolyticus and Regulation of Biofilm Formation by N-(3-Oxodecanoyl) Homoserine Lactone In vitro

    PubMed Central

    Liu, Jianfei; Fu, Kaifei; Wang, Yuxiao; Wu, Chenglin; Li, Fei; Shi, Lei; Ge, Yinlin; Zhou, Lijun

    2017-01-01

    Quorum sensing (QS) is a cell-to-cell communication system based on the exchange of small intercellular signal molecules, such as N-Acyl homoserine lactones (AHLs), which act as cell-density mediators of QS gene expression, and are highly variable both in types and amounts in most Gram-negative Proteobacteria. Understanding the regulation of AHLs may contribute to the elucidation of cell density-dependent phenomena, such as biofilm formation. Vibrio alginolyticus is among the most frequently observed marine opportunistic Vibrio pathogens. However, AHL production of this species and its effects on biofilm formation remain to be understood. Here, our study reported the diverse AHL profiles of 47 marine-isolated V. alginolyticus strains and the effects of exogenous 3-oxo-C10-HSL on biofilm formation under different temperature conditions (16°C and 28°C). A total of 11 detected AHLs were produced by the isolates, of which 3-OH-C4-HSL, 3-oxo-C10-HSL and 3-oxo-C14-HSL comprised the largest proportions. We also observed that moderate levels of exogenous 3-oxo-C10-HSL (10 and 20 μM) could induce or enhance biofilm formation and alter its structure, while high levels (40 and 100 μM) did not significantly improve and even inhibited biofilm formation in V. alginolyticus. Further, regulation by exogenous 3-oxo-C10-HSL was both concentration- and temperature-dependent in V. alginolyticus. PMID:28670299

  3. Pantoea sp. Isolated from Tropical Fresh Water Exhibiting N-Acyl Homoserine Lactone Production

    PubMed Central

    Tan, Wen-Si; Tan, Pui-Wan; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    N-Acyl homoserine lactone (AHL) serves as signaling molecule for quorum sensing (QS) in Gram-negative bacteria to regulate various physiological activities including pathogenicity. With the aim of isolating freshwater-borne bacteria that can cause outbreak of disease in plants and portrayed QS properties, environmental water sampling was conducted. Here we report the preliminary screening of AHL production using Chromobacterium violaceum CV026 and Escherichia coli [pSB401] as AHL biosensors. The 16S rDNA gene sequence of isolate M009 showed the highest sequence similarity to Pantoea stewartii S9-116, which is a plant pathogen. The isolated Pantoea sp. was confirmed to produce N-3-oxohexanoyl-L-HSL (3-oxo-C6-HSL) through analysis of high resolution mass tandem mass spectrometry. PMID:25197715

  4. Pantoea sp. isolated from tropical fresh water exhibiting N-acyl homoserine lactone production.

    PubMed

    Tan, Wen-Si; Muhamad Yunos, Nina Yusrina; Tan, Pui-Wan; Mohamad, Nur Izzati; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    N-Acyl homoserine lactone (AHL) serves as signaling molecule for quorum sensing (QS) in Gram-negative bacteria to regulate various physiological activities including pathogenicity. With the aim of isolating freshwater-borne bacteria that can cause outbreak of disease in plants and portrayed QS properties, environmental water sampling was conducted. Here we report the preliminary screening of AHL production using Chromobacterium violaceum CV026 and Escherichia coli [pSB401] as AHL biosensors. The 16S rDNA gene sequence of isolate M009 showed the highest sequence similarity to Pantoea stewartii S9-116, which is a plant pathogen. The isolated Pantoea sp. was confirmed to produce N-3-oxohexanoyl-L-HSL (3-oxo-C6-HSL) through analysis of high resolution mass tandem mass spectrometry.

  5. Long Chain N-acyl Homoserine Lactone Production by Enterobacter sp. Isolated from Human Tongue Surfaces

    PubMed Central

    Yin, Wai-Fong; Purmal, Kathiravan; Chin, Shenyang; Chan, Xin-Yue; Chan, Kok-Gan

    2012-01-01

    We report the isolation of N-acyl homoserine lactone-producing Enterobacter sp. isolate T1-1 from the posterior dorsal surfaces of the tongue of a healthy individual. Spent supernatants extract from Enterobacter sp. isolate T1-1 activated the biosensor Agrobacterium tumefaciens NTL4(pZLR4), suggesting production of long chain AHLs by these isolates. High resolution mass spectrometry analysis of these extracts confirmed that Enterobacter sp. isolate T1-1 produced a long chain N-acyl homoserine lactone, namely N-dodecanoyl-homoserine lactone (C12-HSL). To the best of our knowledge, this is the first isolation of Enterobacter sp., strain T1-1 from the posterior dorsal surface of the human tongue and N-acyl homoserine lactones production by this bacterium. PMID:23202161

  6. Identification of N-acyl homoserine lactones produced by Gluconacetobacter diazotrophicus PAL5 cultured in complex and synthetic media.

    PubMed

    Nieto-Peñalver, Carlos G; Bertini, Elisa V; de Figueroa, Lucía I C

    2012-07-01

    The endophytic diazotrophic Gluconacetobacter diazotrophicus PAL5 was originally isolated from sugarcane (Saccharum officinarum). The biological nitrogen fixation, phytohormones secretion, solubilization of mineral nutrients and phytopathogen antagonism allow its classification as a plant growth-promoting bacterium. The recent genomic sequence of PAL5 unveiled the presence of a quorum sensing (QS) system. QS are regulatory mechanisms that, through the production of signal molecules or autoinducers, permit a microbial population the regulation of the physiology in a coordinated manner. The most studied autoinducers in gram-negative bacteria are the N-acyl homoserine lactones (AHLs). The usage of biosensor strains evidenced the presence of AHL-like molecules in cultures of G. diazotrophicus PAL5 grown in complex and synthetic media. Analysis of AHLs performed by LC-APCI-MS permitted the identification of eight different signal molecules, including C6-, C8-, C10-, C12- and C14-HSL. Mass spectra confirmed that this diazotrophic strain also synthesizes autoinducers with carbonyl substitutions in the acyl chain. No differences in the profile of AHLs could be determined under both culture conditions. However, although the level of short-chain AHLs was not affected, a decrease of 30% in the production of long-chain AHLs could be measured in synthetic medium.

  7. Inhibitory role of acyl homoserine lactones in hemolytic activity and viability of Streptococcus pyogenes M6 S165

    PubMed Central

    Saroj, Sunil D.; Holmer, Linda; Berengueras, Júlia M.; Jonsson, Ann-Beth

    2017-01-01

    Streptococcus pyogenes an adapted human pathogen asymptomatically colonizes the nasopharynx, among other polymicrobial communities. However, information on the events leading to the colonization and expression of virulence markers subject to interspecies and host-bacteria interactions are limited. The interference of acyl homoserine lactones (AHLs) with the hemolytic activity and viability of S. pyogenes M6 S165 was examined. AHLs, with fatty acid side chains ≥12 carbon atoms, inhibited hemolytic activity by downregulating the expression of the sag operon involved in the production of streptolysin S. Inhibitory AHLs upregulated the expression of transcriptional regulator LuxR. Electrophoretic mobility shift assays revealed the interaction of LuxR with the region upstream of sagA. AHL-mediated bactericidal activity observed at higher concentrations (mM range) was an energy-dependent process, constrained by the requirement of glucose and iron. Ferrichrome transporter FtsABCD facilitated transport of AHLs across the streptococcal membrane. The study demonstrates a previously unreported role for AHLs in S. pyogenes virulence. PMID:28303956

  8. Novel acridine-based N-acyl-homoserine lactone analogs induce endoreduplication in the human oral squamous carcinoma cell line SAS.

    PubMed

    Chai, Hongbo; Hazawa, Masaharu; Hosokawa, Yoichiro; Igarashi, Jun; Suga, Hiroaki; Kashiwakura, Ikuo

    2012-01-01

    The cytotoxicity of novel acridine-based N-acyl-homoserine lactone (AHL) analogs was investigated on the human oral squamous carcinoma cell line SAS. One analog induced G2/M phase arrest at 5.3-10.6 µM and induced polyploidy at a higher dose (21.2 µM). Importantly, treatment of SAS cells with a combination of the AHL analog and the Jun N-terminal kinase (JNK) inhibitor, SP600125, prevented mitosis and induced polyploidy. The AHL analog synergized with X-irradiation to inhibit clonogenic survival of SAS cells; however, its radiosensitizing effects were relative to not X-irradiation-induced apoptosis but mitotic failure following enhanced expression of Aurora A and B. These results suggest that the active AHL analog showed growth-suppressive and radiosensitizing effects, which involve polyploidy followed by G2/M accumulation and atypical cell death in the SAS cell line.

  9. N-Acylhomoserine lactones are potent neutrophil chemoattractants that act via calcium mobilization and actin remodeling.

    PubMed

    Karlsson, Thommie; Musse, Farah; Magnusson, Karl-Eric; Vikström, Elena

    2012-01-01

    In gram-negative bacteria, cell-cell communication based on HSL QS molecules is known to coordinate the production of virulence factors and biofilms. These bacterial signals can also modulate human immune cell behavior. Using a Transwell migration assay, we found that human primary neutrophils are strongly stimulated by 3O-C(12)-HSL and -C(10)-HSL but not C(4)-HSL in a concentration-dependent manner. Moreover, 3O-C(12)-HSL and -C(10)-HSL activate PLCγ1 but not -γ2, mobilize intracellular calcium, and up-regulate IP(3)R. These changes were paralleled by F-actin accumulation, primarily in the leading edge of neutrophils, as evidenced by phalloidin staining and confocal microscopy. F- and G-actin isolation and quantification by immunoblotting revealed that the F/G-actin ratio was increased significantly after treatment with all three HSLs. Furthemore, 3O-C(12)-HSL- and 3O-C(10)-HSL treatment resulted in phosphorylation of Rac1 and Cdc42. In contrast, C(4)-HSL had negligible influence on the phosphorylation status of PLC and Rac1/Cdc42 and failed to attract neutrophils and induce calcium release. The calcium inhibitor thapsigargin, which blocks ER calcium uptake, strongly prevented neutrophil migration toward 3O-C(12)-HSL and -C(10)-HSL. These findings show that the bacterial QS molecules 3O-C(12)-HSL and -C(10)-HSL may attract human neutrophils to the sites of bacterial infection and developing biofilms. Indeed, recognition of HSL QS signals by neutrophils may play a critical role in their recruitment during infections.

  10. Small molecules modulating AHL-based quorum sensing to attenuate bacteria virulence and biofilms as promising antimicrobial drugs.

    PubMed

    Wang, Y; Ma, S

    2014-01-01

    Clinically significant antibiotic resistance is one of the greatest challenges of the twenty-first century. Yet new antibiotics are currently being developed at a much slower pace than our growing need for such drugs. Instead of focusing on conventional therapeutics that target in vitro bacterial viability, an alternative therapy is to target virulence factors and biofilms. Such anti-virulence strategies have attracted more and more attention recently, for it would add both supplement and diversity to our current antimicrobial library. This approach has several potential advantages including imposing less evolutionary pressure on the development of antibiotic resistance, increasing the antibacterial targets and preserving the host endogenous microbiome. Quorum sensing is an intercellular communication process in bacterial communities, which can regulate coordinated expression of virulence factors and biofilms. N-Acyl homoserine lactones (AHLs) are autoinducers generated by a variety of Gram-negative bacteria. These signals combining with their cognate LuxR-type receptors trigger the expression of virulence genes. In this critical review, we summarize various structural types of small molecules targeting AHL-based quorum sensing to attenuate bacteria virulence factors and biofilms.

  11. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria.

    PubMed

    Husain, Fohad M; Ahmad, Iqbal; Khan, Mohammad S; Ahmad, Ejaz; Tahseen, Qudisa; Khan, Mohd Shahnawaz; Alshabib, Nasser A

    2015-01-01

    Bacterial quorum sensing (QS) is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (Mentha piperita) oil was first tested using the Chromobacterium violaceum CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil (PMO) at sub-Minimum Inhibitory Concentrations (sub-MICs) strongly interfered with acyl homoserine lactone (AHL) regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Aeromonas hydrophila. The result of molecular docking analysis attributed the QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors, and biofilm formation indicating broad-spectrum anti-QS activity. Using two Escherichia coli biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs QS systems. Further, findings of the in vivo studies with menthol on nematode model Caenorhabditis elegans showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum QS inhibitor.

  12. Sub-MICs of Mentha piperita essential oil and menthol inhibits AHL mediated quorum sensing and biofilm of Gram-negative bacteria

    PubMed Central

    Husain, Fohad M.; Ahmad, Iqbal; Khan, Mohammad S.; Ahmad, Ejaz; Tahseen, Qudisa; Khan, Mohd Shahnawaz; Alshabib, Nasser A.

    2015-01-01

    Bacterial quorum sensing (QS) is a density dependent communication system that regulates the expression of certain genes including production of virulence factors in many pathogens. Bioactive plant extract/compounds inhibiting QS regulated gene expression may be a potential candidate as antipathogenic drug. In this study anti-QS activity of peppermint (Mentha piperita) oil was first tested using the Chromobacterium violaceum CVO26 biosensor. Further, the findings of the present investigation revealed that peppermint oil (PMO) at sub-Minimum Inhibitory Concentrations (sub-MICs) strongly interfered with acyl homoserine lactone (AHL) regulated virulence factors and biofilm formation in Pseudomonas aeruginosa and Aeromonas hydrophila. The result of molecular docking analysis attributed the QS inhibitory activity exhibited by PMO to menthol. Assessment of ability of menthol to interfere with QS systems of various Gram-negative pathogens comprising diverse AHL molecules revealed that it reduced the AHL dependent production of violacein, virulence factors, and biofilm formation indicating broad-spectrum anti-QS activity. Using two Escherichia coli biosensors, MG4/pKDT17 and pEAL08-2, we also confirmed that menthol inhibited both the las and pqs QS systems. Further, findings of the in vivo studies with menthol on nematode model Caenorhabditis elegans showed significantly enhanced survival of the nematode. Our data identified menthol as a novel broad spectrum QS inhibitor. PMID:26029178

  13. Simultaneous quantitative profiling of N-acyl-L-homoserine lactone and 2-alkyl-4(1H)-quinolone families of quorum-sensing signaling molecules using LC-MS/MS.

    PubMed

    Ortori, Catharine A; Dubern, Jean-Frédéric; Chhabra, Siri Ram; Cámara, Miguel; Hardie, Kim; Williams, Paul; Barrett, David A

    2011-01-01

    An LC-MS/MS method, using positive mode electrospray ionization, for the simultaneous, quantitative and targeted profiling of the N-acyl-L-homoserine lactone (AHL) and 2-alkyl 4-(1H)-quinolone (AQ) families of bacterial quorum-sensing signaling molecules (QSSMs) is presented. This LC-MS/MS technique was applied to determine the relative molar ratios of AHLs and AQs produced by Pseudomonas aeruginosa and the consequences of mutating individual or multiple QSSM synthase genes (lasI, rhlI, pqsA) on AHL and AQ profiles and concentrations. The AHL profile of P. aeruginosa was dominated by N-butanoyl-L-homoserine lactone (C4-HSL) with lesser concentrations of N-hexanoyl-L-homoserine lactone (C6-HSL) and 3-oxo-substituted longer chain AHLs including N-(3-oxodecanoyl)-L-homoserine lactone (3-oxo-C10-HSL) and N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL). The AQ profile of P. aeruginosa comprised the C7 and C9 long alkyl chain AQs including 2-heptyl-4-hydroxyquinoline (HHQ), 2-nonyl-4-hydroxyquinoline, the "pseudomonas quinolone signal" (2-heptyl-3-hydroxy-4-quinolone) and the N-oxides, 2-heptyl-4-hydroxyquinoline N-oxide and 2-nonyl-4-hydroxyquinoline N-oxide. Application of the method showed significant effects of growth medium type on the ratio and the nature of the QSSMs synthesized and the dramatic effect of single, double and triple mutations in the P. aeruginosa QS synthase genes. The LC-MS/MS methodology is applicable in organisms where either or both AHL and AQ QSSMs are produced and can provide comprehensive profiles and concentrations from a single sample.

  14. Production of acylated homoserine lactone by a novel marine strain of Proteus vulgaris and inhibition of its swarming by phytochemicals.

    PubMed

    Biswa, Pramal; Doble, Mukesh

    2014-10-01

    A marine strain of Proteus vulgaris capable of activating multiple acylated homoserine lactone (AHL)-based reporter cultures was isolated. The cognate signal molecule was characterized as octanoyl homoserine lactone (OHL) and its production was observed to be growth dependent, with maximum production (5.675 µg l(-1)) at 24 h growth. The strain exhibited swarming, but its motility was not affected upon addition of pure OHL or culture supernatant. Phytochemicals such as quercitin and berberine chloride inhibited OHL production and reduced swarming. FliA, the predominantly upregulated protein during swarming, was considered as a possible target for these inhibitors, and docking of the two most active and two least active inhibitors to this protein suggested preferential binding of the former set of compounds. Apart from adding new evidence to AHL production in Proteus vulgaris, active inhibitors shortlisted from this study could help in identifying lead compounds to act against this opportunistic pathogen of the respiratory and gastrointestinal tract.

  15. Tropodithietic Acid Production in Phaeobacter gallaeciensis Is Regulated by N-Acyl Homoserine Lactone-Mediated Quorum Sensing▿

    PubMed Central

    Berger, Martine; Neumann, Alexander; Schulz, Stefan; Simon, Meinhard; Brinkhoff, Thorsten

    2011-01-01

    The production of N-acyl homoserine lactones (AHLs) is widely distributed within the marine Roseobacter clade, and it was proposed that AHL-mediated quorum sensing (QS) is one of the most common cell-to-cell communication mechanisms in roseobacters. The traits regulated by AHL-mediated QS are yet not known for members of the Roseobacter clade, but production of the antibiotic tropodithietic acid (TDA) was supposed to be controlled by AHL-mediated QS in Phaeobacter spp. We describe here for the first time the functional role of luxR and luxI homologous genes of an organism of the Roseobacter clade, i.e., pgaR and pgaI in Phaeobacter gallaeciensis. Our results demonstrate that the AHL synthase gene pgaI is responsible for production of N-3-hydroxydecanoylhomoserine lactone (3OHC10-HSL). Insertion mutants of pgaI and pgaR are both deficient in TDA biosynthesis and the formation of a yellow-brown pigment when grown in liquid marine broth medium. This indicates that in P. gallaeciensis the production of both secondary metabolites is controlled by AHL-mediated QS. Quantitative real-time PCR showed that the transcription level of tdaA, which encodes an essential transcriptional regulator for TDA biosynthesis, decreased 28- and 51-fold in pgaI and pgaR genetic backgrounds, respectively. These results suggest that both the response regulator PgaR and the 3OHC10-HSL produced by PgaI induce expression of tdaA, which in turn positively regulates expression of the tda genes. Moreover, we confirmed that TDA can also act as autoinducer in P. gallaeciensis, as previously described for Silicibacter sp. strain TM1040, but only in the presence of the response regulator PgaR. PMID:21949069

  16. Three-dimensional structure of the quorum-quenching N-acyl homoserine lactone hydrolase from Bacillus thuringiensis

    PubMed Central

    Liu, Dali; Lepore, Bryan W.; Petsko, Gregory A.; Thomas, Pei W.; Stone, Everett M.; Fast, Walter; Ringe, Dagmar

    2005-01-01

    The three-dimensional structure of the N-acyl-l-homoserine lactone hydrolase (AHL lactonase) from Bacillus thuringiensis has been determined, by using single-wavelength anomalous dispersion (SAD) phasing, to 1.6-Å resolution. AHLs are produced by many Gram-negative bacteria as signaling molecules used in quorum-sensing pathways that indirectly sense cell density and regulate communal behavior. Because of their importance in pathogenicity, quorum-sensing pathways have been suggested as potential targets for the development of novel therapeutics. Quorum-sensing can be disrupted by enzymes evolved to degrade these lactones, such as AHL lactonases. These enzymes are members of the metallo-β-lactamase superfamily and contain two zinc ions in their active sites. The zinc ions are coordinated to a number of ligands, including a single oxygen of a bridging carboxylate and a bridging water/hydroxide ion, thought to be the nucleophile that hydrolyzes the AHLs to ring-opened products, which can no longer act as quorum signals. PMID:16087890

  17. Design, synthesis, and biological evaluation of abiotic, non-lactone modulators of LuxR-type quorum sensing

    PubMed Central

    McInnis, Christine E.; Blackwell, Helen E.

    2011-01-01

    Quorum sensing (QS) is a cell-cell signaling mechanism that allows bacteria to monitor their population size and alter their behavior at high cell densities. Gram-negative bacteria use N-acylated L-homoserine lactones (AHLs) as their primary signals for QS. These signals are susceptible to lactone hydrolysis in biologically relevant media, and the ring-opened products are inactive QS signals. We have previously identified a range of non-native AHLs capable of strongly agonizing and antagonizing QS in Gram-negative bacteria. However, these abiotic AHLs are also prone to hydrolysis and inactivation and thereby have a relatively short time window for use (~12–48 h). Non-native QS modulators with reduced or no hydrolytic instability could have enhanced potencies and would be valuable as tools to study the mechanisms of QS in a range of environments (for example, on eukaryotic hosts). This study reports the design and synthesis of two libraries of new, non-hydrolyzable AHL mimics. The libraries were screened for QS modulatory activity using LasR, LuxR, and TraR bacterial reporter strains, and several new, abiotic agonists and antagonists of these receptors were identified. PMID:21798749

  18. Design, synthesis, and biological evaluation of abiotic, non-lactone modulators of LuxR-type quorum sensing.

    PubMed

    McInnis, Christine E; Blackwell, Helen E

    2011-08-15

    Quorum sensing (QS) is a cell-cell signaling mechanism that allows bacteria to monitor their population size and alter their behavior at high cell densities. Gram-negative bacteria use N-acylated L-homoserine lactones (AHLs) as their primary signals for QS. These signals are susceptible to lactone hydrolysis in biologically relevant media, and the ring-opened products are inactive QS signals. We have previously identified a range of non-native AHLs capable of strongly agonizing and antagonizing QS in Gram-negative bacteria. However, these abiotic AHLs are also prone to hydrolysis and inactivation and thereby have a relatively short time window for use (∼12-48 h). Non-native QS modulators with reduced or no hydrolytic instability could have enhanced potencies and would be valuable as tools to study the mechanisms of QS in a range of environments (for example, on eukaryotic hosts). This study reports the design and synthesis of two libraries of new, non-hydrolyzable AHL mimics. The libraries were screened for QS modulatory activity using LasR, LuxR, and TraR bacterial reporter strains, and several new, abiotic agonists and antagonists of these receptors were identified. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Influence of bacterial N-acyl-homoserine lactones on growth parameters, pigments, antioxidative capacities and the xenobiotic phase II detoxification enzymes in barley and yam bean.

    PubMed

    Götz-Rösch, Christine; Sieper, Tina; Fekete, Agnes; Schmitt-Kopplin, Philippe; Hartmann, Anton; Schröder, Peter

    2015-01-01

    Bacteria are able to communicate with each other and sense their environment in a population density dependent mechanism known as quorum sensing (QS). N-acyl-homoserine lactones (AHLs) are the QS signaling compounds of Gram-negative bacteria which are frequent colonizers of rhizospheres. While cross-kingdom signaling and AHL-dependent gene expression in plants has been confirmed, the responses of enzyme activities in the eukaryotic host upon AHLs are unknown. Since AHL are thought to be used as so-called plant boosters or strengthening agents, which might change their resistance toward radiation and/or xenobiotic stress, we have examined the plants' pigment status and their antioxidative and detoxifying capacities upon AHL treatment. Because the yield of a crop plant should not be negatively influenced, we have also checked for growth and root parameters. We investigated the influence of three different AHLs, namely N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL), and N-decanoyl- homoserine lactone (C10-HSL) on two agricultural crop plants. The AHL-effects on Hordeum vulgare (L.) as an example of a monocotyledonous crop and on the tropical leguminous crop plant Pachyrhizus erosus (L.) were compared. While plant growth and pigment contents in both plants showed only small responses to the applied AHLs, AHL treatment triggered tissue- and compound-specific changes in the activity of important detoxification enzymes. The activity of dehydroascorbate reductase in barley shoots after C10-HSL treatment for instance increased up to 384% of control plant levels, whereas superoxide dismutase activity in barley roots was decreased down to 23% of control levels upon C6-HSL treatment. Other detoxification enzymes reacted similarly within this range, with interesting clusters of positive or negative answers toward AHL treatment. In general the changes on the enzyme level were more severe in barley than in yam bean which might be due to the different abilities of the plants to

  20. Influence of bacterial N-acyl-homoserine lactones on growth parameters, pigments, antioxidative capacities and the xenobiotic phase II detoxification enzymes in barley and yam bean

    PubMed Central

    Götz-Rösch, Christine; Sieper, Tina; Fekete, Agnes; Schmitt-Kopplin, Philippe; Hartmann, Anton; Schröder, Peter

    2015-01-01

    Bacteria are able to communicate with each other and sense their environment in a population density dependent mechanism known as quorum sensing (QS). N-acyl-homoserine lactones (AHLs) are the QS signaling compounds of Gram-negative bacteria which are frequent colonizers of rhizospheres. While cross-kingdom signaling and AHL-dependent gene expression in plants has been confirmed, the responses of enzyme activities in the eukaryotic host upon AHLs are unknown. Since AHL are thought to be used as so-called plant boosters or strengthening agents, which might change their resistance toward radiation and/or xenobiotic stress, we have examined the plants’ pigment status and their antioxidative and detoxifying capacities upon AHL treatment. Because the yield of a crop plant should not be negatively influenced, we have also checked for growth and root parameters. We investigated the influence of three different AHLs, namely N-hexanoyl- (C6-HSL), N-octanoyl- (C8-HSL), and N-decanoyl- homoserine lactone (C10-HSL) on two agricultural crop plants. The AHL-effects on Hordeum vulgare (L.) as an example of a monocotyledonous crop and on the tropical leguminous crop plant Pachyrhizus erosus (L.) were compared. While plant growth and pigment contents in both plants showed only small responses to the applied AHLs, AHL treatment triggered tissue- and compound-specific changes in the activity of important detoxification enzymes. The activity of dehydroascorbate reductase in barley shoots after C10-HSL treatment for instance increased up to 384% of control plant levels, whereas superoxide dismutase activity in barley roots was decreased down to 23% of control levels upon C6-HSL treatment. Other detoxification enzymes reacted similarly within this range, with interesting clusters of positive or negative answers toward AHL treatment. In general the changes on the enzyme level were more severe in barley than in yam bean which might be due to the different abilities of the plants to

  1. Influence of food system conditions on N-acyl-L-homoserine lactones production by Aeromonas spp.

    PubMed

    Medina-Martínez, M S; Uyttendaele, M; Demolder, V; Debevere, J

    2006-12-01

    Eleven of 13 Aeromonas strains were shown to produce AHLs. Results of TLC showed that N-butanoyl-L-homoserine lactone (C4-HSL) was the main AHL produced in LB medium at 30 degrees C. The influence of different carbon sources, temperature, pH values and salt concentrations on AHL production was determined in eight A. hydrophila and one A. caviae strain. Additionally a quantitative study of C4-HSL production by A. hydrophila strain 519 under different conditions was performed. Positive results were found in the AHL induction assay for some Aeromonas strains in cultures in LB agar incubated at 12 degrees C after 72-96 h. The induction of the sensor strains by Aeromonas spp. occurred in LB medium supplemented with all carbon sources in a concentration of 0.5%. The production of C4-HSL by A. hydrophila 519 was found until 3.5% (w/v) of NaCl. For pHs close to the neutrality the C4-HSL production by A. hydrophila was evident after 24-48 h of incubation. A. hydrophila 519 produced C4-HSL under anaerobic conditions. Also, the AHL production by Aeromonas strains was studied in simulate agar of shrimp, fish and some vegetables. The production of AHLs was evident by almost all the test strains in shrimp simulated agar. In fish agar only for one of three fish species tested, positive results were found. Induction assay in vegetables simulated agar showed principally negative results, probably because of the presence of inhibitory compounds in these vegetables.

  2. Multiplicity of Quorum Quenching Enzymes: A Potential Mechanism to Limit Quorum Sensing Bacterial Population.

    PubMed

    Koul, Shikha; Kalia, Vipin Chandra

    2017-03-01

    Bacteria express certain of their characteristics especially, pathogenicity factors at high cell densities. The process is termed as quorum sensing (QS). QS operates via signal molecules such as acylhomoserine lactones (AHLs). Other bacteria inhibit QS through the inactivation of AHL signals by producing enzymes like AHL-lactonases and -acylases. Comparative genomic analysis has revealed the multiplicity of genes for AHL lactonases (up to 12 copies per genome) among Bacillus spp. and that of AHL-acylases (up to 5 copies per genome) among Pseudomonas spp. This genetic evolution can be envisaged to enable host to withstand the attacks from bacterial population, which regulates its functioning through QS.

  3. Deinococcus radiodurans can interfere with quorum sensing by producing an AHL-acylase and an AHL-lactonase.

    PubMed

    Koch, Gudrun; Nadal-Jimenez, Pol; Cool, Robbert H; Quax, Wim J

    2014-07-01

    Bacterial communication via the secretion of small diffusible compounds allows microorganisms to regulate gene expression in a coordinated manner. As many virulence traits are regulated in this fashion, disruption of chemical communication has been proposed as novel antimicrobial therapy. Quorum-quenching enzymes have been a promising discovery in this field as they interfere with the communication of Gram-negative bacteria. AHL-lactonases and AHL-acylases have been described in a variety of bacterial strains; however, usually only one of these two groups of enzymes has been described in a single species. We report here the presence of a member of each group of enzymes in the extremophile bacterium Deinococcus radiodurans. Co-occurrence of both enzymes in a single species increases the chance of inactivating foreign AHL signals under different conditions. We demonstrate that both enzymes are able to degrade the quorum-sensing molecules of various pathogens subsequently affecting virulence gene expression. These studies add the quorum-quenching enzymes of D. radiodurans to the list of potent quorum-quenchers and highlight the idea that quorum quenching could have evolved in some bacteria as a strategy to gain a competitive advantage by altering gene expression in other species.

  4. Effect of small chain N acyl homoserine lactone quorum sensing signals on biofilms of food-borne pathogens.

    PubMed

    A, Jamuna Bai; V, Ravishankar Rai

    2016-09-01

    Quorum sensing or cell to cell communication which includes inter- and intra-cellular communication has been implicated in the production of virulence factor and formation of biofilm in food-borne pathogens. In the present study, the effect of quorum sensing signals on the biofilms of food-borne pathogens has been elucidated. N-butryl homoserine lactone and N-hexanoyl homoserine lactone belonging to acyl homoserine lactone (AHL) family of signaling molecules were investigated for their effect on the biofilm formation (attachment and exopolymeric substance production) in the food-borne pathogens Escherichia coli, Salmonella enterica serovar Typhimurium and Vibrio parahemolyticus. The signaling molecules at a concentration of 1 µM were capable of increasing biofilm formation in all the tested pathogens. There was an increase in the attachment of the bacterial cells and biomass as observed by microtiter plate assay and exopolymeric substances production in the biofilms in presence of the AHLs. Further, it needs to be elucidated if the effect of AHLS on the biofilms of E. coli and S. enterica serovar Typhimurium is SdiA dependent.

  5. Topical Administration of Acylated Homoserine Lactone Improves Epithelialization of Cutaneous Wounds in Hyperglycaemic Rats

    PubMed Central

    Kitamura, Aya; Quinetti, Paes C.; Nakagami, Gojiro; Mugita, Yuko; Oe, Makoto; Noguchi, Hiroshi; Mori, Taketoshi; Sanada, Hiromi

    2016-01-01

    Clinicians often experience delayed epithelialization in diabetic patients, for which a high glucose condition is one of the causes. However, the mechanisms underlying delayed wound closure have not been fully elucidated, and effective treatments to enhance epithelialization in patients with hyperglycaemia have not been established. Here we propose a new reagent, acylated homoserine lactone (AHL), to improve the delayed epithelialization due to the disordered formation of a basement membrane of epidermis in hyperglycaemic rats. Acute hyperglycaemia was induced by streptozotocin injection in this experiment. Full thickness wounds were created on the flanks of hyperglycaemic or control rats. Histochemical and immunohistochemical analyses were performed to identify hyperglycaemia-specific abnormalities in epidermal regeneration by comparison between groups. We then examined the effects of AHL on delayed epithelialization in hyperglycaemic rats. Histological analysis showed the significantly shorter epithelializing tissue (P < 0.05), abnormal structure of basement membrane (fragmentation and immaturity), and hypo- and hyperproliferation of basal keratinocytes in hyperglycaemic rats. Treating the wound with AHL resulted in the decreased abnormalities of basement membrane, normal distribution of proliferating epidermal keratinocytes, and significantly promoted epithelialization (P < 0.05) in hyperglycemic rats, suggesting the improving effects of AHL on abnormal epithelialization due to hyperglycemia. PMID:27404587

  6. Bacterial signals N-acyl homoserine lactones induce the changes of morphology and ethanol tolerance in Saccharomyces cerevisiae.

    PubMed

    Ren, Ge; Ma, Anzhou; Liu, Weifeng; Zhuang, Xuliang; Zhuang, Guoqiang

    2016-12-01

    The bacterial quorum sensing signals N-acyl homoserine lactone (AHL) signals are able to regulate a diverse array of physiological activities, such as symbiosis, virulence and biofilm formation, depending on population density. Recently, it has been discovered that the bacterial quorum sensing (QS) signal molecules can induce extensive response of higher eukaryotes including plants and mammalian cells. However, little is known about the response of fungi reacting to these bacterial signals. Here we showed that Saccharomyces cerevisiae, as an ancient eukaryote and widely used for alcoholic beverage and bioethanol production, exposed to short-chain 3-OC6-HSL and long-chain C12-HSL appeared obvious changes in morphology and ethanol tolerance. AHLs could increase the frequency of cells with bipolar and multipolar buds, and these changes did not present distinct differences when induced by different types (3-OC6-HSL and C12-HSL) and varied concentrations (200 nM and 2 μM) of AHLs. Further investigation by flow cytometer displayed that the cells untreated by AHLs reduced cell size (decreased FSC) and enhanced intracellular density (increased in SSC), compared with the AHLs-induced cells after incubation 6 h. In addition, the long-chain C12-HSL could slightly increase the ethanol tolerance of S. cerevisiae while the short-chain HSL obviously decreased it. Our study would be valuable to further research on the interaction between prokaryotic and eukaryotic microbes, and be reference for industrial production of bioethanol.

  7. Variations on a theme: diverse N-acyl homoserine lactone-mediated quorum sensing mechanisms in gram-negative bacteria.

    PubMed

    Smith, Debra; Wang, Jin-Hong; Swatton, Jane E; Davenport, Peter; Price, Bianca; Mikkelsen, Helga; Stickland, Hannah; Nishikawa, Kahoko; Gardiol, Noémie; Spring, David R; Welch, Martin

    2006-01-01

    Many Gram-negative bacteria employ a mechanism of cell-cell communication known as quorum sensing (QS). The role of QS is to enable the cells in a culture to coordinate their gene expression profile with changes in the population cell density. The best characterized mechanisms of QS employ N-acylated homoserine lactones (AHLs) as signalling molecules. These AHLs are made by enzymes known as LuxI homologs, and accumulate in the culture supernatant at a rate proportional to the increase in cell density. Once the AHL concentration exceeds a certain threshold value, these ligands bind to intracellular receptors known as LuxR homologs. The latter are transcriptional regulators, whose activity alters upon binding the AHL ligand, thereby eliciting a change in gene transcription. Over the last five years, it has become increasingly obvious that this is a rather simplistic view of AHL-dependent QS, and that in fact, there is considerable diversity in the way in which LuxI-R homologs operate. The aim of the current review is to describe these variations on the basic theme, and to show how functional genomics is revolutionizing our understanding of QS-controlled regulons.

  8. Short Chain N-Acyl Homoserine Lactone Production in Tropical Marine Vibrio sinaloensis Strain T47

    PubMed Central

    Tan, Pui-Wan; Tan, Wen-Si; Yunos, Nina Yusrina Muhamad; Mohamad, Nur Izzati; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Quorum sensing (QS), acts as one of the gene regulatory systems that allow bacteria to regulate their physiological activities by sensing the population density with synchronization of the signaling molecules that they produce. Here, we report a marine isolate, namely strain T47, and its unique AHL profile. Strain T47 was identified using 16S rRNA sequence analysis confirming that it is a member of Vibrio closely clustered to Vibrio sinaloensis. The isolated V. sinaloensis strain T47 was confirmed to produce N-butanoyl-L-homoserine lactone (C4-HSL) by using high resolution liquid chromatography tandem mass spectrometry. V. sinaloensis strain T47 also formed biofilms and its biofilm formation could be affected by anti-QS compound (cathechin) suggesting this is a QS-regulated trait in V. sinaloensis strain T47. To our knowledge, this is the first documentation of AHL and biofilm production in V. sinaloensis strain T47. PMID:25046018

  9. Quorum Sensing N-acyl Homoserine Lactones-SdiA Suppresses Escherichia coli-Pseudomonas aeruginosa Conjugation through Inhibiting traI Expression

    PubMed Central

    Lu, Yang; Zeng, Jianming; Wu, Binning; E, Shunmei; Wang, Lina; Cai, Renxin; Zhang, Ni; Li, Youqiang; Huang, Xianzhang; Huang, Bin; Chen, Cha

    2017-01-01

    Conjugation is a key mechanism for horizontal gene transfer and plays an important role in bacterial evolution, especially with respect to antibiotic resistance. However, little is known about the role of donor and recipient cells in regulation of conjugation. Here, using an Escherichia coli (SM10λπ)-Pseudomonas aeruginosa (PAO1) conjugation model, we demonstrated that deficiency of lasI/rhlI, genes associated with generation of the quorum sensing signals N-acyl homoserine lactones (AHLs) in PAO1, or deletion of the AHLs receptor SdiA in the donor SM10λπ both facilitated conjugation. When using another AHLs-non-producing E. coli strain EC600 as recipient cells, deficiency of sdiA in donor SM10λπ hardly affect the conjugation. More importantly, in the presence of exogenous AHLs, the conjugation efficiency between SM10λπ and EC600 was dramatically decreased, while deficiency of sdiA in SM10λπ attenuated AHLs-inhibited conjugation. These data suggest the conjugation suppression function of AHLs-SdiA chemical signaling. Further bioinformatics analysis, β-galactosidase reporter system and electrophoretic mobility shift assays characterized the binding site of SdiA on the promoter region of traI gene. Furthermore, deletion of lasI/rhlI or sdiA promoted traI mRNA expression in SM10λπ and PAO1 co-culture system, which was abrogated by AHLs. Collectively, our results provide new insight into an important contribution of quorum sensing system AHLs-SdiA to the networks that regulate conjugation. PMID:28164039

  10. Involvement of calmodulin in regulation of primary root elongation by N-3-oxo-hexanoyl homoserine lactone in Arabidopsis thaliana

    PubMed Central

    Zhao, Qian; Zhang, Chao; Jia, Zhenhua; Huang, Yali; Li, Haili; Song, Shuishan

    2015-01-01

    Many bacteria use signal molecules of low molecular weight to monitor their local population density and to coordinate their collective behavior in a process called “quorum sensing” (QS). N-acyl-homoserine lactones (AHLs) are the primary QS signals among Gram-negative bacteria. AHL-mediated QS plays an essential role in diverse bacterial physiological processes. Recent evidence shows that plants are able to sense bacterial AHLs and respond to them appropriately. However, little is known about the mechanism by which plants perceive and transduce the bacterial AHLs within cells. In this study, we found that the stimulatory effect of N-3-oxo-hexanoyl homoserine lactone (3OC6-HSL) on primary root elongation of Arabidopsis was abolished by the calmodulin (CaM) antagonists N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7) and trifluoperazine (TFP). Western-blot and ELISA analysis revealed that the concentration of CaM protein in Arabidopsis roots increased after treatment with 1 μM 3OC6-HSL. Results from quantitative RT-PCR demonstrated that the transcription of all nine CaM genes in Arabidopsis genome was up-regulated in the plants treated with 3OC6-HSL. The loss-of-function mutants of each AtCaM gene (AtCaM1-9) were insensitive to 3OC6-HSL-stimulation of primary root elongation. On the other hand, the genetic evidence showed that CaM may not participates the inhibition of primary root length caused by application of long-chained AHLs such as C10-HSL and C12-HSL. Nevertheless, our results suggest that CaM is involved in the bacterial 3OC6-HSL signaling in plant cells. These data offer new insight into the mechanism of plant response to bacterial QS signals. PMID:25628641

  11. Detection of Quorum Sensing Activity in the Multidrug-Resistant Clinical Isolate Pseudomonas aeruginosa Strain GB11

    PubMed Central

    Cheng, Huey Jia; Ee, Robson; Cheong, Yuet Meng; Tan, Wen-Si; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    A multidrug-resistant clinical bacteria strain GB11 was isolated from a wound swab on the leg of a patient. Identity of stain GB11 as Pseudomonas aeruginosa was validated by using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Detection of the production of signaling molecules, N-acylhomoserine lactones (AHLs), was conducted using three different bacterial biosensors. A total of four different AHLs were found to be produced by strain GB11, namely N-butyryl homoserine lactone (C4-HSL), N-hexanoylhomoserine lactone (C6-HSL), N-octanoyl homoserine lactone (C8-HSL) and N-3-oxo-dodecanoylhomoserine lactone (3-oxo-C12-HSL) using high resolution liquid chromatography tandem mass spectrometry (LC-MS/MS). Of these detected AHLs, 3-oxo-C12-HSL was found to be the most abundant AHL produced by P. aeruginosa GB11. PMID:25019635

  12. Effects of quorum quenching by AHL lactonase on AHLs, protease, motility and proteome patterns in Aeromonas veronii LP-11.

    PubMed

    Gui, Meng; Wu, Ruiyun; Liu, Lei; Wang, Shun; Zhang, Li; Li, Pinglan

    2017-07-03

    Food spoilage by some bacteria is reported to be regulated by quorum sensing (QS). In this study, a quorum quenching approach was used to investigate the QS regulated phenotypes (growth, protease and motility) and proteins expression in of Aeromonas veronii LP-11, which is a specific spoilage organism of sturgeon. AHL lactonase AiiAAI96 from Bacillus quenched the QS system, probably by enzymatically inactivating the AHLs produced by A. veronii LP-11. After AiiAAI96 treatment, the protease and motility activities of A. veronii LP-11 were reduced, but cell growth was not affected. Proteome analysis revealed thirty-two proteins that were differentially expressed within cells treated with AiiAAI96 at early stationary phase, and that are functionally involved in metabolite transport, amino acid metabolism, central metabolism, respiration, transcription and translation, suggesting that QS may globally coordinate the metabolic processes within A. veronii LP-11 cells. Some of these QS regulated proteins were identified to be potentially participated in nutrient acquirement from environment and spoilage behavior of the organism. Indeed, AiiAAI96 treatment inhibited the spoilage progress of vacuum-packaged sturgeon stored at 4°C. These results highlight that the QS is a major metabolism regulator within A. veronii LP-11 cells and participates in sturgeon spoilage. Copyright © 2017. Published by Elsevier B.V.

  13. Diverse Profiles of N-acyl Homoserine L-Lactones, Biofilm, Virulence Genes and Integrons in Food-Borne Aeromonas Isolates.

    PubMed

    Nagar, Vandan; Sinha, Vibha; Bandekar, Jayant R

    2015-08-01

    Aeromonas are regarded as opportunistic as well as primary pathogens of humans and fish, and are associated with gastroenteritis and septicemia in humans. Production of N-acyl-homoserine lactone (AHL) signal molecules and biofilm was determined in 22 Aeromonas isolates, from different food products in India, using thin-layer chromatography (TLC) analysis and microtiter-plate assay, respectively. Overall, highly heterogeneous patterns of AHL production were observed, with the production of N-butanoyl homoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL) by the majority (81.8%) of Aeromonas food isolates. Moreover, putative N-pentanoyl homoserine lactone (C5-HSL), N-heptanoyl homoserine lactone (C7-HSL), and N-octanoyl homoserine lactone (C8-HSL) were produced by 72.7%, 27.3%, and 9.1% of isolates, respectively. This is the 1st report of production of C7-HSL by Aeromonas species. Aeromonas food isolates were highly variable in their biofilm forming abilities with majority of them as weak biofilm producers in 2 different media, TSB and M9 minimal medium supplemented with 0.4% glucose. The genes encoding for putative virulence factors, glycerophospholipid cholesterol acyltransferase (gcat), heat-labile cytotonic enterotoxin (alt), heat-stable cytotonic enterotoxin (ast), serine protease (ser), polar flagella (fla), and lateral flagella (lafA) were present in 95.5%, 59.1%, 22.7%, 81.8%, 77.3%, and 22.7% of the strains, respectively. Class 1 integrons (100 to 3000 bp) were found in 68.2% of food isolates; whereas, 50% isolates contained class 2 integrons (150 to 1600 bp). This study provides a baseline data on the diversity of AHLs, biofilm forming ability and presence of virulence genes and integrons in Aeromonas food isolates from India.

  14. A novel gene OsAHL1 improves both drought avoidance and drought tolerance in rice

    PubMed Central

    Zhou, Liguo; Liu, Zaochang; Liu, Yunhua; Kong, Deyan; Li, Tianfei; Yu, Shunwu; Mei, Hanwei; Xu, Xiaoyan; Liu, Hongyan; Chen, Liang; Luo, Lijun

    2016-01-01

    A novel gene, OsAHL1, containing an AT-hook motif and a PPC domain was identified through genome-wide profiling and analysis of mRNAs by comparing the microarray of drought-challenged versus normally watered rice. The results indicated OsAHL1 has both drought avoidance and drought tolerance that could greatly improve drought resistance of the rice plant. Overexpression of OsAHL1 enhanced multiple stress tolerances in rice plants during both seedling and panicle development stages. Functional studies revealed that OsAHL1 regulates root development under drought condition to enhance drought avoidance, participates in oxidative stress response and also regulates the content of chlorophyll in rice leaves. OsAHL1 specifically binds to the A/T rich sequence region of promoters or introns, and hence directly regulates the expression of many stress related downstream genes. PMID:27453463

  15. The Systematic Investigation of the Quorum Sensing System of the Biocontrol Strain Pseudomonas chlororaphis subsp. aurantiaca PB-St2 Unveils aurI to Be a Biosynthetic Origin for 3-Oxo-Homoserine Lactones

    PubMed Central

    Bauer, Judith S.; Hauck, Nils; Christof, Lisa; Mehnaz, Samina; Gust, Bertolt; Gross, Harald

    2016-01-01

    The shoot endophytic biocontrol strain Pseudomonas chlororaphis subsp. aurantiaca PB-St2 produces a wide range of exoproducts, including enzymes and antibiotics. The production of exoproducts is commonly tightly regulated. In order to get a deeper insight into the regulatory network of PB-St2, the strain was systematically investigated regarding its quorum sensing systems, both on the genetic and metabolic level. The genome analysis of PB-St2 revealed the presence of four putative acyl homoserine lactone (AHL) biosynthesis genes: phzI, csaI, aurI, and hdtS. LC-MS/MS analyses of the crude supernatant extracts demonstrated that PB-St2 produces eight AHLs. In addition, the concentration of all AHL derivatives was quantified time-resolved in parallel over a period of 42 h during the growth of P. aurantiaca PB-St2, resulting in production curves, which showed differences regarding the maximum levels of the AHLs (14.6 nM– 1.75 μM) and the production period. Cloning and heterologous overexpression of all identified AHL synthase genes in Escherichia coli proved the functionality of the resulting synthases PhzI, CsaI, and AurI. A clear AHL production pattern was assigned to each of these three AHL synthases, while the HdtS synthase did not lead to any AHL production. Furthermore, the heterologous expression study demonstrated unequivocally and for the first time that AurI directs the synthesis of two 3-oxo-AHLs. PMID:27861617

  16. Mutational analysis of the quorum-sensing receptor LasR reveals interactions that govern activation and inhibition by non-lactone ligands

    PubMed Central

    Gerdt, Joseph P.; McInnis, Christine E.; Schell, Trevor L.; Rossi, Francis M.; Blackwell, Helen E.

    2014-01-01

    SUMMARY Gram-negative bacteria use N-acyl L-homoserine lactone (AHL) quorum sensing (QS) signals to regulate the expression of myriad phenotypes. Non-native AHL analogs can strongly attenuate QS receptor activity and thereby QS signaling; however, we currently lack a molecular understanding of the mechanisms by which most of these compounds elicit their agonistic or antagonistic profiles. In this study, we investigated the origins of striking activity profile switches (i.e., receptor activator to inhibitor, and vice versa) observed upon alteration of the lactone head group in certain AHL analogs. Reporter gene assays of mutant versions of the Pseudomonas aeruginosa QS receptor LasR revealed that interactions between the ligands and Trp60, Tyr56, and Ser129 govern whether these ligands behave as LasR activators or inhibitors. Using this knowledge, we propose a model for the modulation of LasR by AHL analogs—encompassing a subtly different interaction with the binding pocket to a global change in LasR conformation. PMID:25242287

  17. Plant responses to bacterial N-acyl L-homoserine lactones are dependent on enzymatic degradation to L-homoserine.

    PubMed

    Palmer, Andrew G; Senechal, Amanda C; Mukherjee, Arijit; Ané, Jean-Michel; Blackwell, Helen E

    2014-08-15

    Many bacteria use quorum sensing (QS) to regulate phenotypes that ultimately benefit the bacterial population at high cell densities. These QS-dependent phenotypes are diverse and can have significant impacts on the bacterial host, including virulence factor production, motility, biofilm formation, bioluminescence, and root nodulation. As bacteria and their eukaryotic hosts have coevolved over millions of years, it is not surprising that certain hosts appear to be able to sense QS signals, potentially allowing them to alter QS outcomes. Recent experiments have established that eukaryotes have marked responses to the N-acyl L-homoserine lactone (AHL) signals used by Gram-negative bacteria for QS, and the responses of plants to AHLs have received considerable scrutiny to date. However, the molecular mechanisms by which plants, and eukaryotes in general, sense bacterial AHLs remain unclear. Herein, we report a systematic analysis of the responses of the model plants Arabidopsis thaliana and Medicago truncatula to a series of native AHLs and byproducts thereof. Our results establish that AHLs can significantly alter seedling growth in an acyl-chain length dependent manner. Based upon A. thaliana knockout studies and in vitro biochemical assays, we conclude that the observed growth effects are dependent upon AHL amidolysis by a plant-derived fatty acid amide hydrolase (FAAH) to yield L-homoserine. The accumulation of l-homoserine appears to encourage plant growth at low concentrations by stimulating transpiration, while higher concentrations inhibit growth by stimulating ethylene production. These results offer new insights into the mechanisms by which plant hosts can respond to QS signals and the potential role of QS in interkingdom associations.

  18. Validity and Redescription of Profundulus balsanus Ahl, 1935 (Cyprinodontiformes: Profundulidae).

    PubMed

    Jamangapé O, José A; Velázquez-Velázquez, Ernesto; Martínez-Ramirez, Emilio; Anzueto-Calvo, Manuel J; Gomez, Eyda L; Dominguez-Cisneros, Sara E; Mcmahan, Caleb D; Matamoros, Wilfredo A

    2016-10-02

    Profundulus balsanus was described by Ahl in 1935 and later placed in synonymy with P. punctatus. Recent molecular studies have demonstrated that specimens identified as P. balsanus belong to a distinct taxon. Herein we used a combination of morphometric, meristic, coloration and osteological data in order to demonstrate the distinctiveness of P. balsanus. Additionally, we used molecular data to reconstruct a phylogeny to place P. balsanus in a systematic context. Profundulus balsanus belongs to the punctatus clade within the genus Profundulus. It can be distinguished from P. oaxacae based on scale count in the lateral line and from P. punctatus based on differences in coloration in the anal fin. We provide a taxonomic key to all Mexican species of Profundulus.

  19. Lactones. 6. Microbial lactonization of gamma,delta-epoxy esters.

    PubMed

    Olejniczak, T; Gawroński, J; Wawrzeńczyk, C

    2001-06-01

    The ability of 19 microorganisms to perform the enantioselective lactonization of racemic gamma,delta-epoxy ester 3a and its 7-methyl homolog 3b was checked. It was found that Rhodotorula rubra preferentialy transformed both substrates to (-)-enantiomers of trans delta-hydroxy-gamma-lactones with ee 76% for 3a and 24% for 3b. The best efficiency (20-30%) and enantioselectivity (ee 60-100%) of formation of (-)-gamma-hydroxy-delta-lactones 6a and 6b was observed for lactonization by Botrytis cinerea and Fusarium semitectum, respectively.

  20. Identification and Quantification of N-Acyl Homoserine Lactones Involved in Bacterial Communication by Small-Scale Synthesis of Internal Standards and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Leipert, Jan; Treitz, Christian; Leippe, Matthias; Tholey, Andreas

    2017-08-01

    N-acyl homoserine lactones (AHL) are small signal molecules involved in the quorum sensing of many gram-negative bacteria, and play an important role in biofilm formation and pathogenesis. Present analytical methods for identification and quantification of AHL require time-consuming sample preparation steps and are hampered by the lack of appropriate standards. By aiming at a fast and straightforward method for AHL analytics, we investigated the applicability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Suitable MALDI matrices, including crystalline and ionic liquid matrices, were tested and the fragmentation of different AHL in collision-induced dissociation MS/MS was studied, providing information about characteristic marker fragments ions. Employing small-scale synthesis protocols, we established a versatile and cost-efficient procedure for fast generation of isotope-labeled AHL standards, which can be used without extensive purification and yielded accurate standard curves. Quantitative analysis was possible in the low pico-molar range, with lower limits of quantification reaching from 1 to 5 pmol for different AHL. The developed methodology was successfully applied in a quantitative MALDI MS analysis of low-volume culture supernatants of Pseudomonas aeruginosa. [Figure not available: see fulltext.

  1. Sesquiterpene lactones from Staehelina fruticosa.

    PubMed

    Kotsos, Maria P; Aligiannis, Nektarios; Myrianthopoulos, Vasillios; Mitaku, Sofia; Skaltsounis, Leandros

    2008-05-01

    The phytochemical analysis of Staehelina fruticosa led to the isolation of four germacranolide-type sesquiterpene lactones (1- 4), including two new glycosides. The structures of these sesquiterpene lactones were elucidated using spectroscopic techniques, and enzymatic hydrolysis was carried out to confirm the nature of the two glycoside derivatives. Molecular modeling was incorporated to substantiate their relative configuration.

  2. Systemic Responses of Barley to the 3-hydroxy-decanoyl-homoserine Lactone Producing Plant Beneficial Endophyte Acidovorax radicis N35

    PubMed Central

    Han, Shengcai; Li, Dan; Trost, Eva; Mayer, Klaus F.; Vlot, A. Corina; Heller, Werner; Schmid, Michael; Hartmann, Anton; Rothballer, Michael

    2016-01-01

    Quorum sensing auto-inducers of the N-acyl homoserine lactone (AHL) type produced by Gram-negative bacteria have different effects on plants including stimulation on root growth and/or priming or acquirement of systemic resistance in plants. In this communication the influence of AHL production of the plant growth promoting endophytic rhizosphere bacterium Acidovorax radicis N35 on barley seedlings was investigated. A. radicis N35 produces 3-hydroxy-C10-homoserine lactone (3-OH-C10-HSL) as the major AHL compound. To study the influence of this QS autoinducer on the interaction with barley, the araI-biosynthesis gene was deleted. The comparison of inoculation effects of the A. radicis N35 wild type and the araI mutant resulted in remarkable differences. While the N35 wild type colonized plant roots effectively in microcolonies, the araI mutant occurred at the root surface as single cells. Furthermore, in a mixed inoculum the wild type was much more prevalent in colonization than the araI mutant documenting that the araI mutation affected root colonization. Nevertheless, a significant plant growth promoting effect could be shown after inoculation of barley with the wild type and the araI mutant in soil after 2 months cultivation. While A. radicis N35 wild type showed only a very weak induction of early defense responses in plant RNA expression analysis, the araI mutant caused increased expression of flavonoid biosynthesis genes. This was corroborated by the accumulation of several flavonoid compounds such as saponarin and lutonarin in leaves of root inoculated barley seedlings. Thus, although the exact role of the flavonoids in this plant response is not clear yet, it can be concluded, that the synthesis of AHLs by A. radicis has implications on the perception by the host plant barley and thereby contributes to the establishment and function of the bacteria-plant interaction. PMID:28018401

  3. N-Acyl-Homoserine Lactone Confers Resistance toward Biotrophic and Hemibiotrophic Pathogens via Altered Activation of AtMPK61[C][W

    PubMed Central

    Schikora, Adam; Schenk, Sebastian T.; Stein, Elke; Molitor, Alexandra; Zuccaro, Alga; Kogel, Karl-Heinz

    2011-01-01

    Pathogenic and symbiotic bacteria rely on quorum sensing to coordinate the collective behavior during the interactions with their eukaryotic hosts. Many Gram-negative bacteria use N-acyl-homoserine lactones (AHLs) as signals in such communication. Here we show that plants have evolved means to perceive AHLs and that the length of acyl moiety and the functional group at the γ position specify the plant’s response. Root treatment with the N-3-oxo-tetradecanoyl-L-homoserine lactone (oxo-C14-HSL) reinforced the systemic resistance to the obligate biotrophic fungi Golovinomyces orontii in Arabidopsis (Arabidopsis thaliana) and Blumeria graminis f. sp. hordei in barley (Hordeum vulgare) plants. In addition, oxo-C14-HSL-treated Arabidopsis plants were more resistant toward the hemibiotrophic bacterial pathogen Pseudomonas syringae pv tomato DC3000. Oxo-C14-HSL promoted a stronger activation of mitogen-activated protein kinases AtMPK3 and AtMPK6 when challenged with flg22, followed by a higher expression of the defense-related transcription factors WRKY22 and WRKY29, as well as the PATHOGENESIS-RELATED1 gene. In contrast to wild-type Arabidopsis and mpk3 mutant, the mpk6 mutant is compromised in the AHL effect, suggesting that AtMPK6 is required for AHL-induced resistance. Results of this study show that AHLs commonly produced in the rhizosphere are crucial factors in plant pathology and could be an agronomic issue whose full impact has to be elucidated in future analyses. PMID:21940998

  4. Lactones. 9. Synthesis of terpenoid lactones-active insect antifeedants.

    PubMed

    Paruch, E; Ciunik, Z; Nawrot, J; Wawrzeńczyk, C

    2000-10-01

    Starting from (+)- and (-)-perillyl alcohols, via Claisen rearrangement and iodolactonization, four enantiomeric pairs of gamma-lactones were obtained. The structures of compounds were established by both spectroscopic and crystallographic methods. The lactones were tested for antifeeding activity toward grain storage pests-the granary weevil beetle (Sitophilus granarius L.), the khapra beetle (Trogoderma granarium Ev.), and the confused flour beetle (Tribolium confusum Duv.). The results of the tests proved that two compounds, (1R,4R, 6R)-(-)-4-(1-methylethenyl)-9-oxabicyclo[4.3.0]nonan-8-one (8a) and its enantiomer (8b), are very active antifeedants against all of the above tested species. The lactone 8b is also active against the peach-potato aphid (Myzus persicae Sulz.). The activity depends on the absolute configurations of compound chiral centers. Additionally, the lactones 8a and 8b are characterized by interesting fragrances.

  5. Microbial Reduction of Ketopantoyl Lactone to Pantoyl Lactone1

    PubMed Central

    Lanzilotta, Raymond P.; Bradley, Dorothy G.; McDonald, Kerry M.

    1974-01-01

    The results of a microbial survey study have shown that the ability to reduce added ketopantoic acid (or ketopantoyl lactone) and accumulate pantoic acid (or pantoyl lactone) in the growth medium is widespread among diverse fungi. The reductions generally proceeded with less than full stereoselectivity. However, specific strains of the ascomycete Byssochlamys fulva were found to form D[-]-pantoic acid in unusually high yields and optical purity. PMID:4589122

  6. Regulation of the violacein biosynthetic gene cluster by acylhomoserine lactone-mediated quorum sensing in Chromobacterium violaceum ATCC 12472.

    PubMed

    Morohoshi, Tomohiro; Fukamachi, Katsumasa; Kato, Masashi; Kato, Norihiro; Ikeda, Tsukasa

    2010-01-01

    Chromobacterium violaceum produces the purple pigment violacein by quorum-sensing regulation. 20-bp of the lux box-like sequence was found upstream of vioA in C. violaceum ATCC 12472. CviR received C10-HSL and C6-HSL and activated the transcription of vioA in Escherichia coli. However, in strain ATCC 12472, C6-HSL inhibited both C10-HSL-mediated violacein production and the transcription of vioA.

  7. Complete genome sequencing of Pandoraea pnomenusa RB38 and Molecular Characterization of Its N-acyl homoserine lactone synthase gene ppnI

    PubMed Central

    Lim, Yan-Lue; Ee, Robson; How, Kah-Yan; Lee, Siew-Kim; Yong, Delicia; Tee, Kok Keng; Yin, Wai-Fong

    2015-01-01

    In this study, we sequenced the genome of Pandoraea pnomenusa RB38 using Pacific Biosciences RSII (PacBio) Single Molecule Real Time (SMRT) sequencing technology. A pair of cognate luxI/R homologs was identified where the luxI homolog, ppnI, was found adjacent to a luxR homolog, ppnR1. An additional orphan luxR homolog, ppnR2, was also discovered. Multiple sequence alignment and phylogenetic analysis revealed that ppnI is an N-acyl homoserine lactone (AHL) synthase gene that is distinct from those of the nearest phylogenetic neighbor viz. Burkholderia spp. High resolution tandem mass spectrometry (LC-MS/MS) analysis showed that Escherichia coli BL21 harboring ppnI produced a similar AHL profile (N-octanoylhomoserine lactone, C8-HSL) as P. pnomenusa RB38, the wild-type donor strain, confirming that PpnI directed the synthesis of AHL in P. pnomenusa RB38. To our knowledge, this is the first documentation of the luxI/R homologs of the genus Pandoraea. PMID:26336650

  8. Quorum Sensing Activity of Hafnia alvei Isolated from Packed Food

    PubMed Central

    Tan, Jia-Yi; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Quorum sensing (QS) is a mechanism adopted by bacteria to regulate expression of genes according to population density. N-acylhomoserine lactones (AHLs) are a type of QS signalling molecules commonly found in Gram-negative bacteria which have been reported to play a role in microbial spoilage of foods and pathogenesis. In this study, we isolated an AHL-producing Hafnia alvei strain (FB1) from spherical fish pastes. Analysis via high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) on extracts from the spent supernatant of H. alvei FB1 revealed the existence of two short chain AHLs: N-(3-oxohexanoyl) homoserine lactone (3-oxo-C6-HSL) and N-(3-oxo- octanoyl) homoserine lactone (3-oxo-C8-HSL). To our knowledge, this is the first report of the production of AHLs, especially 3-oxo-C8-HSL, by H. alvei. PMID:24736131

  9. Detection and characterization of N-acyl-l-homoserine lactones using GFP-based biosensors in conjunction with thin-layer chromatography.

    PubMed

    Charlesworth, James; Kimyon, Onder; Manefield, Michael; Burns, Brendan P

    2015-11-01

    Many microorganisms use quorum sensing to regulate several complex phenotypes, and this is accomplished by the release of a signal molecule(s) into the environment. N-acyl-homoserine lactones (AHLs) are a common class of signalling molecule utilized by a range of microorganisms (primarily Gram negative bacteria but most recently also archaea) and are often detected through the use of bacterial biosensors. Biosensors can be limited by both their specificity and sensitivity, and the aim of this study was to modify and improve current AHL detection strategies. The biosensor employed in the present study was Escherichia coli MT102 harbouring a plasmid containing a LuxR based biosensor, which produces green fluorescent protein (GFP) as a reporting mechanism. A new method of visualizing the GFP based biosensor overlaid on silica sheets for the purpose of thin-layer chromatography (TLC) is presented. This new method vastly improves sensitivity of AHL detection by a GFP biosensor than previously reported and as such represents a powerful new tool in AHL research. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Interference with the germination and growth of Ulva zoospores by quorum-sensing molecules from Ulva-associated epiphytic bacteria.

    PubMed

    Twigg, Matthew S; Tait, Karen; Williams, Paul; Atkinson, Steve; Cámara, Miguel

    2014-02-01

    Ulva zoospores preferentially settle on N-acylhomoserine lactone (AHL) producing marine bacterial biofilms. To investigate whether AHL signal molecules also affect the success and rate of zoospore germination in addition to zoospore attraction, the epiphytic bacteria associated with mature Ulva linza were characterized and bacterial isolates representative of this community tested for the ability to produce AHLs. Two of these AHL-producing isolates, Sulfitobacter spp. 376 and Shewanella spp. 79, were transformed with plasmids expressing the Bacillus spp. AHL lactonase gene aiiA to generate AHL-deficient variants. The germination and growth of U. linza zoospores was studied in the presence of these AHL-deficient strains and their AHL-producing counterparts. This revealed that the AHLs produced by Sulfitobacter spp. and Shewanella spp. or the bacterial products they regulate have a negative impact on both zoospore germination and the early growth of the Ulva germling. Further experiments with Escherichia coli biofilms expressing recombinant AHL synthases and synthetic AHLs provide data to demonstrate that zoospores germinated and grown in the absence of AHLs were significantly longer than those germinated in the presence of AHLs. These results reveal an additional role for AHLs per se in the interactive relationships between marine bacteria and Ulva zoospores.

  11. Thematic Issue: Protists

    PubMed Central

    Twigg, Matthew S; Tait, Karen; Williams, Paul; Atkinson, Steve; Cámara, Miguel

    2014-01-01

    Ulva zoospores preferentially settle on N-acylhomoserine lactone (AHL) producing marine bacterial biofilms. To investigate whether AHL signal molecules also affect the success and rate of zoospore germination in addition to zoospore attraction, the epiphytic bacteria associated with mature Ulva linza were characterized and bacterial isolates representative of this community tested for the ability to produce AHLs. Two of these AHL-producing isolates, Sulfitobacter spp. 376 and Shewanella spp. 79, were transformed with plasmids expressing the Bacillus spp. AHL lactonase gene aiiA to generate AHL-deficient variants. The germination and growth of U. linza zoospores was studied in the presence of these AHL-deficient strains and their AHL-producing counterparts. This revealed that the AHLs produced by Sulfitobacter spp. and Shewanella spp. or the bacterial products they regulate have a negative impact on both zoospore germination and the early growth of the Ulva germling. Further experiments with Escherichia coli biofilms expressing recombinant AHL synthases and synthetic AHLs provide data to demonstrate that zoospores germinated and grown in the absence of AHLs were significantly longer than those germinated in the presence of AHLs. These results reveal an additional role for AHLs per se in the interactive relationships between marine bacteria and Ulva zoospores. PMID:23879807

  12. The status of Leptopelis barbouri Ahl, 1929 and eleven other nomina of the current tree-frog genus Leptopelis (Arthroleptidae) described from East Africa, with a redescription of Leptopelis grandiceps Ahl, 1929.

    PubMed

    Gvoždík, Václav; Tillack, Frank; Menegon, Michele; Loader, Simon P

    2014-04-28

    An investigation of name-bearing types and other relevant type specimens of twelve nominal Leptopelis taxa described from or distributed in the Eastern Arc Mountains in East Africa was carried out. Our aim was to clarify their status and where necessary revise respective nomina. We suggest several nomenclatural and taxonomic actions: 1) Leptopelis barbouri Ahl, 1929 is transferred to the synonymy of Leptopelis flavomaculatus (Günther, 1864) as a junior subjective synonym; 2) Leptopelis grandiceps Ahl, 1929 is resurrected from the synonymy of Leptopelis uluguruensis Barbour & Loveridge, 1928 as a valid species conforming to the tree frogs which have been known as 'L. barbouri' and a lectotype is designated; 3) Leptopelis usambarae Ahl, 1929 is transferred from the synonymy of L. uluguruensis Barbour & Loveridge, 1928 to the synonymy of L. grandiceps Ahl, 1929 as a subjective synonym; 4) a lectotype of Leptopelis amaniensis Ahl, 1929 (synonym of L. uluguruensis), Hylambates johnstoni Boulenger, 1897 (synonym of L. flavomaculatus) and Leptopelis signifer Ahl, 1929 (synonym of L. vermiculatus) is designated to stabilize identity of the nomina; and 5) the type locality of Leptopelis martiensseni Ahl, 1929 and Leptopelis tanganus Ahl, 1929 is corrected.

  13. N-acyl Homoserine Lactone-Producing Pseudomonas putida Strain T2-2 from Human Tongue Surface

    PubMed Central

    Chen, Jian-Woon; Chin, Shenyang; Tee, Kok Keng; Yin, Wai-Fong; Choo, Yeun Mun; Chan, Kok-Gan

    2013-01-01

    Bacterial cell-to-cell communication (quorum sensing) refers to the regulation of bacterial gene expression in response to changes in microbial population density. Quorum sensing bacteria produce, release and respond to chemical signal molecules called autoinducers. Bacteria use two types of autoinducers, namely autoinducer-1 (AI-1) and autoinducer-2 (AI-2) where the former are N-acylhomoserine lactones and the latter is a product of the luxS gene. Most of the reported literatures show that the majority of oral bacteria use AI-2 for quorum sensing but rarely the AI-1 system. Here we report the isolation of Pseudomonas putida strain T2-2 from the oral cavity. Using high resolution mass spectrometry, it is shown that this isolate produced N-octanoylhomoserine lactone (C8-HSL) and N-dodecanoylhomoserine lactone (C12-HSL) molecules. This is the first report of the finding of quorum sensing of P. putida strain T2-2 isolated from the human tongue surface and their quorum sensing molecules were identified. PMID:24084113

  14. N-acyl homoserine lactone-producing Pseudomonas putida strain T2-2 from human tongue surface.

    PubMed

    Chen, Jian-Woon; Chin, Shenyang; Tee, Kok Keng; Yin, Wai-Fong; Choo, Yeun Mun; Chan, Kok-Gan

    2013-09-30

    Bacterial cell-to-cell communication (quorum sensing) refers to the regulation of bacterial gene expression in response to changes in microbial population density. Quorum sensing bacteria produce, release and respond to chemical signal molecules called autoinducers. Bacteria use two types of autoinducers, namely autoinducer-1 (AI-1) and autoinducer-2 (AI-2) where the former are N-acylhomoserine lactones and the latter is a product of the luxS gene. Most of the reported literatures show that the majority of oral bacteria use AI-2 for quorum sensing but rarely the AI-1 system. Here we report the isolation of Pseudomonas putida strain T2-2 from the oral cavity. Using high resolution mass spectrometry, it is shown that this isolate produced N-octanoylhomoserine lactone (C8-HSL) and N-dodecanoylhomoserine lactone (C12-HSL) molecules. This is the first report of the finding of quorum sensing of P. putida strain T2-2 isolated from the human tongue surface and their quorum sensing molecules were identified.

  15. A proteomic analysis of Arabidopsis thaliana seedling responses to 3-oxo-octanoyl-homoserine lactone, a bacterial quorum-sensing signal

    SciTech Connect

    Miao, Chunjuan; Liu, Fang; Zhao, Qian; Jia, Zhenhua; Song, Shuishan

    2012-10-19

    Highlights: Black-Right-Pointing-Pointer 3OC8-HSL can change the expression of diverse proteins in Arabidopsis. Black-Right-Pointing-Pointer 3OC8-HSL responsive proteins were identified using MALDI-TOF-MS. Black-Right-Pointing-Pointer Plant could have an extensive range of functional responses to bacterial AHL. -- Abstract: N-acyl-homoserine lactones (AHLs) are a class of bacterial quorum-sensing (QS) signals that are commonly used by Gram-negative bacteria for cell-to-cell communication. Recently, it has become evident that AHLs can regulate plant root growth and trigger plant defense responses; however, little is known about the plant response mechanisms to bacterial QS signals. In this study, we used a proteomic approach to investigate the responses of Arabidopsis thaliana seedlings to N-3-oxo-octanoyl-homoserine lactone (3OC8-HSL), a bacterial QS signal. The results revealed that the abundance of 53 protein spots was significantly altered; two thirds of these proteins were found to be up-regulated after 3OC8-HSL treatment. Thirty-four proteins were identified using MALDI-TOF-MS. These 3OC8-HSL-responsive proteins, in addition to one protein of unknown function, are implicated in a variety of physiological processes, including metabolism of carbohydrate and energy, protein biosynthesis and quality control systems, defense response and signal transduction and cytoskeleton remodeling. Our bioinformatic analysis indicated that the chloroplasts are the intracellular organelles most influenced by the exposure to 3OC8-HSL. Our data indicate that plants have an extensive range of functional responses to bacterial AHLs that may play important roles in the interaction between plants and bacteria.

  16. The Arabidopsis thaliana DNA-binding protein AHL19 mediates verticillium wilt resistance.

    PubMed

    Yadeta, Koste A; Hanemian, Mathieu; Smit, Patrick; Hiemstra, Jelle A; Pereira, Andy; Marco, Yves; Thomma, Bart P H J

    2011-12-01

    Verticillium spp. are destructive soilborne fungal pathogens that cause vascular wilt diseases in a wide range of plant species. Verticillium wilts are particularly notorious, and genetic resistance in crop plants is the most favorable means of disease control. In a gain-of-function screen using an activation-tagged Arabidopsis mutant collection, we identified four mutants, A1 to A4, which displayed enhanced resistance toward the vascular wilt species Verticillium dahliae, V. albo-atrum and V. longisporum but not to Fusarium oxysporum f. sp. raphani. Further testing revealed that mutant A2 displayed enhanced Ralstonia solanacearum resistance, while mutants A1 and A3 were more susceptible toward Pseudomonas syringae pv. tomato. Identification of the activation tag insertion site in the A1 mutant revealed an insertion in close proximity to the gene encoding AHL19, which was constitutively expressed in the mutant. AHL19 knock-out alleles were found to display enhanced Verticillium susceptibility whereas overexpression of AHL19 resulted in enhanced Verticillium resistance, showing that AHL19 acts as a positive regulator of plant defense.

  17. An Interview with Mark Ahlness and Jean Carmody about the Earth Day Groceries Project.

    ERIC Educational Resources Information Center

    Strangman, Nicole

    2002-01-01

    Outlines an interview with Mark Ahlness, a third-grade teacher at Arbor Heights Elementary School in Seattle, Washington, and Jean Carmody, an art teacher at two elementary schools in Cranston, Rhode Island. Describes their collaborative project called the Earth Day Groceries Project. Explains that in this Internet project, students decorate…

  18. Inhibiting N-acyl-homoserine lactone synthesis and quenching Pseudomonas quinolone quorum sensing to attenuate virulence

    PubMed Central

    Chan, Kok-Gan; Liu, Yi-Chia; Chang, Chien-Yi

    2015-01-01

    Bacteria sense their own population size, tune the expression of responding genes, and behave accordingly to environmental stimuli by secreting signaling molecules. This phenomenon is termed as quorum sensing (QS). By exogenously manipulating the signal transduction bacterial population behaviors could be controlled, which may be done through quorum quenching (QQ). QS related regulatory networks have been proven their involvement in regulating many virulence determinants in pathogenic bacteria in the course of infections. Interfering with QS signaling system could be a novel strategy against bacterial infections and therefore requires more understanding of their fundamental mechanisms. Here we review the development of studies specifically on the inhibition of production of N-acyl-homoserine lactone (AHL), a common proteobacterial QS signal. The opportunistic pathogen, Pseudomonas aeruginosa, equips the alkylquinolone (AQ)-mediated QS which also plays crucial roles in its pathogenicity. The studies in QQ targeting on AQ are also discussed. PMID:26539190

  19. Sesquiterpene lactones from Taraxacum obovatum.

    PubMed

    Michalska, Klaudia; Kisiel, Wanda

    2003-02-01

    Two new guaianolide glucosides, deacetylmatricarin 8-O-beta-glucopyranoside and 11beta-hydroxyleukodin 11-O-beta-glucopyranoside, were isolated from roots of Taraxacum obovatum, along with four known sesquiterpene lactones, deacetylmatricarin, sonchuside A, taraxinic acid beta-glucopyranosyl ester and its 11beta,13-dihydro derivative. Their structures were established by spectral methods.

  20. Impact of phenolic compounds in the acyl homoserine lactone-mediated quorum sensing regulatory pathways.

    PubMed

    Hossain, Md Akil; Lee, Seung-Jin; Park, Na-Hye; Mechesso, Abraham Fikru; Birhanu, Biruk Tesfaye; Kang, JeongWoo; Reza, Md Ahsanur; Suh, Joo-Won; Park, Seung-Chun

    2017-09-06

    Quorum sensing (QS) is a cell density-dependent regulation of virulent bacterial gene expression by autoinducers that potentially pertains in the epidemic of bacterial virulence. This study was initially designed to evaluate the effect of 5 phenolic compounds in the modulation of QS and virulence factors of Chromobacterium violaceum and Pseudomonas aeruginosa, and to determine the mechanisms of their effects. Biosensor strains were used to assess antibacterial and anti-QS effect of these compounds. Only methyl gallate (MG) among these compounds demonstrated profound anti-QS effect in the preliminary study, and thus only MG was utilized further to evaluate the effects on the synthesis and activity of acyl homoserine lactone (AHL) in C. violaceum and on the modulation of biofilm, motility, proteolytic, elastase, pyocyanin, and rhamnolipid activity in P. aeruginosa. Finally, the effect of MG on the expression of QS-regulated genes of P. aeruginosa was verified. MG suppressed both the synthesis and activity of AHL in C. violaceum. It also restricted the biofilm formation and other QS-associated virulence factor of P. aeruginosa. MG concentration-dependently suppressed the expression of lasI/R, rhlI/R, and pqsA of P. aeruginosa and was non-toxic in in vitro study. This is the first report of the anti-QS mechanism of MG.

  1. Diversity of culturable bacterial communities in the intestinal tracts of goldfish (Carassius auratus) and their ability to produce N-acyl homoserine lactone.

    PubMed

    Sugita, Haruo; Kitao, Shun; Narisawa, Satoshi; Minamishima, Ryosuke; Itoi, Shiro

    2017-01-26

    Intestinal bacteria isolated from goldfish (Carassius auratus) were identified based on 16 ribosomal RNA (rRNA) gene sequences and screened for their ability to produce N-acyl homoserine lactone (AHL), an autoinducer of the quorum sensing (QS) system. The 230 aerobes/facultative anaerobes that were isolated comprised members of the genera Aeromonas (184 isolates), Citrobacter (11), Enterobacter (2), Shewanella (28), Vagococcus (1), and Vibrio (4). Among these genera, the two most abundant species were Aeromonas veronii (163 isolates) and Shewanella xiamenensis (27). In addition, 142 obligate anaerobes consisting of Cetobacterium somerae (139 isolates), Clostridium frigidicarnis (2), and Cetobacterium sp. (1) were also isolated. One hundred seventy isolates (74.2%) belonging to the genera Aeromonas, Citrobacter, Enterobacter, Shewanella, and Vibrio produced AHL, while 155 (67.7%) and 91 (39.7%) isolates possessed the luxR and luxI gene homologs, respectively. None of the obligate anaerobes produced AHL or possessed luxRI homologs. Total viable counts ranged from 1.2 × 10(7) to 2.2 × 10(9) CFU/g, which were accounted for 0.8 to 15.2% of direct counts. Aeromonas veronii, S. xiamenensis, and C. somerae were detected from five goldfish at densities ranging from 4.0 × 10(6) to 1.7 × 10(9) CFU/g, indicating that these bacteria are dominant components of the culturable gut flora in goldfish. In addition, members of the genera Aeromonas and Shewanella appeared to communicate with each other by using the QS system to some extent when the concentration of AHL reaches a certain threshold. It is therefore suggested that bacteria with the ability to disrupt AHL secretion in intestinal environments are potential candidates for probionts for preventing opportunistic infections in freshwater fish such as goldfish.

  2. Membrane fouling induced by AHL-mediated soluble microbial product (SMP) formation by fouling-causing bacteria co-cultured with fouling-enhancing bacteria.

    PubMed

    Ishizaki, So; Sugiyama, Ryoichi; Okabe, Satoshi

    2017-08-16

    Membrane fouling still remains a major obstacle for wider applications of membrane bioreactor (MBR), which is mainly caused by soluble microbial products (SMP). Identification of key bacteria responsible for SMP production is essential for mitigation of membrane fouling. Here, we investigated the effect of microbial interaction on membrane fouling. We measured the membrane fouling potentials of 13 bacterial strains isolated from a pilot-scale MBR treating domestic wastewater when they were cultivated as single-culture and co-culture. We found that fouling-causing bacteria (FCB) displayed much higher fouling potential when co-cultured even with non-FCB and mixed population (activated sludge). In particular, the fouling potential of strain S26, one of FCB, increased 26.8 times when cultivated with strain S22 (fouling-enhancing bacteria, FEB). The secretion of N-octanoyl-L-homoserine lactone (C8-HSL) was increased by co-cultivating S22 and S26 as compared with cultivating as single culture, which stimulated the production of fouling-causing SMP by S26 and consequently resulted in severe membrane fouling. This result suggests that AHL-mediated quorum-sensing (QS) regulatory system was involved in secretion of fouling-causing SMP.

  3. Quorum sensing in Yersinia enterocolitica controls swimming and swarming motility.

    PubMed

    Atkinson, Steve; Chang, Chien-Yi; Sockett, R Elizabeth; Cámara, Miguel; Williams, Paul

    2006-02-01

    The Yersinia enterocolitica LuxI homologue YenI directs the synthesis of N-3-(oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL). In a Y. enterocolitica yenI mutant, swimming motility is temporally delayed while swarming motility is abolished. Since both swimming and swarming are flagellum dependent, we purified the flagellin protein from the parent and yenI mutant. Electrophoresis revealed that in contrast to the parent strain, the yenI mutant grown for 17 h at 26 degrees C lacked the 45-kDa flagellin protein FleB. Reverse transcription-PCR indicated that while mutation of yenI had no effect on yenR, flhDC (the motility master regulator) or fliA (the flagellar sigma factor) expression, fleB (the flagellin structural gene) was down-regulated. Since 3-oxo-C6-HSL and C6-HSL did not restore swimming or swarming in the yenI mutant, we reexamined the N-acylhomoserine lactone (AHL) profile of Y. enterocolitica. Using AHL biosensors and mass spectrometry, we identified three additional AHLs synthesized via YenI: N-(3-oxodecanoyl)homoserine lactone, N-(3-oxododecanoyl)homoserine lactone (3-oxo-C12-HSL), and N-(3-oxotetradecanoyl)homoserine lactone. However, none of the long-chain AHLs either alone or in combination with the short-chain AHLs restored swarming or swimming in the yenI mutant. By investigating the transport of radiolabeled 3-oxo-C12-HSL and by introducing an AHL biosensor into the yenI mutant we demonstrate that the inability of exogenous AHLs to restore motility to the yenI mutant is not related to a lack of AHL uptake. However, both AHL synthesis and motility were restored by complementation of the yenI mutant with a plasmid-borne copy of yenI.

  4. Carbohydrate-Based Lactones: Synthesis and Applications

    NASA Astrophysics Data System (ADS)

    Xavier, Nuno M.; Rauter, Amélia P.; Queneau, Yves

    The synthesis and uses of different kinds of carbohydrate-based lactones are described. This group of compounds includes aldonolactones, other related monocyclic lactones and bicyclic systems. The latter can arise from uronic acids, carboxymethyl ethers or glycosides, or from C-branched sugars.

  5. Unusual Long-Chain N-Acyl Homoserine Lactone Production by and Presence of Quorum Quenching Activity in Bacterial Isolates from Diseased Tilapia Fish

    PubMed Central

    Chang, Chien-Yi; Koh, Chong-Lek; Sam, Choon-Kook; Chan, Xin-Yue; Yin, Wai Fong; Chan, Kok Gan

    2012-01-01

    Growth-dependent cell-cell communication termed quorum sensing is a key regulatory system in bacteria for controlling gene expression including virulence factors. In this study five potential bacterial pathogens including Bacillus sp. W2.2, Klebsiella sp. W4.2, Pseudomonas sp. W3 and W3.1 and Serratia sp. W2.3 were isolated from diseased Tilapia fish in Malaysia, supplied by the leading global fish supplier. Proteolytic activity assays confirmed that with the exception of Klebsiella sp. W4.2, all isolates showed distinct proteolytic activity. Furthermore Bacillus sp. W2.2 and Pseudomonas sp. strains W3 and W3.1 also displayed haemolytic activity. By using high resolution liquid chromatography mass spectrometry, we revealed the presence of unusually long-chain N-(3-oxohexadecanoyl)-homoserine lactone (3-oxo-C16-HSL) from Pseudomonas sp. W3.1 and N-dodecanoyl-homoserine lactone (C12-HSL) from Serratia sp. W2.3, respectively. Interestingly, Pseudomonas sp. W3.1 also produced a wide range of Pseudomonas quinolone signalling (PQS) molecules. Pseudomonas sp. W3 did not show any quorum sensing properties but possessed quorum quenching activity that inactivated AHLs. This study is the first documentation that shows unusual long-chain AHLs production in Serratia sp. and Pseudomonas sp. isolated from diseased fish and the latter also produce a wide range of PQS molecules. PMID:22952864

  6. Exploring the active site of acyl homoserine lactones-dependent transcriptional regulators with bacterial quorum sensing modulators using molecular mechanics and docking studies.

    PubMed

    Soulère, Laurent; Frezza, Marine; Queneau, Yves; Doutheau, Alain

    2007-09-01

    A comparative molecular modelling study of acyl homoserine lactones-dependent transcriptional regulators (TraR, SdiA, LuxR and LasR) involved in bacterial quorum sensing (QS) revealed a high structural homology of their active site. Docking studies within the active site of TraR of fixed conformations obtained using molecular mechanics calculations showed that TraR, for which the crystalline structure is known, is a relevant model for the study of other protein-ligand interactions in the same protein family. Structure-activity relationships of AHLs derived QS modulators including carboxamides, sulfonamides and ureas were thus investigated. The results show that Tyr61, a residue conserved in the LuxR-proteins family, is involved in attractive interactions with aromatic carboxamide antagonists. Tyr53, Tyr61 and Asp70, conserved residues, are implicated in both the development of additional hydrogen bonds and attractive interactions with the N-sulfonyl homoserine lactones and AHLs derived ureas antagonists.

  7. N-acyl-homoserine lactone-mediated regulation of phenazine gene expression by Pseudomonas aureofaciens 30-84 in the wheat rhizosphere.

    PubMed Central

    Wood, D W; Gong, F; Daykin, M M; Williams, P; Pierson, L S

    1997-01-01

    Pseudomonas aureofaciens 30-84 is a soilborne bacterium that colonizes the wheat rhizosphere. This strain produces three phenazine antibiotics which suppress take-all disease of wheat by inhibition of the causative agent Gaeumannomyces graminis var. tritici. Phenazines also enhance survival of 30-84 within the wheat rhizosphere in competition with other organisms. Expression of the phenazine biosynthetic operon is controlled by the phzR/phzI N-acyl-homoserine lactone (AHL) response system (L. S. Pierson III et al., J. Bacterial 176:3966-3974, 1994; D. W. Wood and L. S. Pierson III, Gene 168:49-53, 1996). By using high-pressure liquid chromatography coupled with high-resolution mass spectrometry, the AHL produced by PhzI has now been identified as N-hexanoyl-homoserine lactone (HHL). In addition, the ability of HHL to serve as an interpopulation signal molecule in the wheat rhizosphere has been examined by using isogenic reporter strains. Disruption of phzI reduced expression of the phenazine biosynthetic operon 1,000-fold in the wheat rhizosphere. Coinoculation of an isogenic strain which produced the endogenous HHL signal restored phenazine gene expression in the phzI mutant to wild-type levels in situ. These results demonstrate that HHL is required for phenazine expression in situ and is an effective interpopulation signal molecule in the wheat rhizosphere. PMID:9401023

  8. Unusual long-chain N-acyl homoserine lactone production by and presence of quorum quenching activity in bacterial isolates from diseased tilapia fish.

    PubMed

    Chang, Chien-Yi; Koh, Chong-Lek; Sam, Choon-Kook; Chan, Xin-Yue; Yin, Wai Fong; Chan, Kok Gan

    2012-01-01

    Growth-dependent cell-cell communication termed quorum sensing is a key regulatory system in bacteria for controlling gene expression including virulence factors. In this study five potential bacterial pathogens including Bacillus sp. W2.2, Klebsiella sp. W4.2, Pseudomonas sp. W3 and W3.1 and Serratia sp. W2.3 were isolated from diseased Tilapia fish in Malaysia, supplied by the leading global fish supplier. Proteolytic activity assays confirmed that with the exception of Klebsiella sp. W4.2, all isolates showed distinct proteolytic activity. Furthermore Bacillus sp. W2.2 and Pseudomonas sp. strains W3 and W3.1 also displayed haemolytic activity. By using high resolution liquid chromatography mass spectrometry, we revealed the presence of unusually long-chain N-(3-oxohexadecanoyl)-homoserine lactone (3-oxo-C16-HSL) from Pseudomonas sp. W3.1 and N-dodecanoyl-homoserine lactone (C12-HSL) from Serratia sp. W2.3, respectively. Interestingly, Pseudomonas sp. W3.1 also produced a wide range of Pseudomonas quinolone signalling (PQS) molecules. Pseudomonas sp. W3 did not show any quorum sensing properties but possessed quorum quenching activity that inactivated AHLs. This study is the first documentation that shows unusual long-chain AHLs production in Serratia sp. and Pseudomonas sp. isolated from diseased fish and the latter also produce a wide range of PQS molecules.

  9. Phenotypic and genotypic characterisation of Burkholderia cenocepacia J2315 mutants affected in homoserine lactone and diffusible signal factor-based quorum sensing systems suggests interplay between both types of systems.

    PubMed

    Udine, Claudia; Brackman, Gilles; Bazzini, Silvia; Buroni, Silvia; Van Acker, Heleen; Pasca, Maria Rosalia; Riccardi, Giovanna; Coenye, Tom

    2013-01-01

    Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS) circuits. These QS systems either use N-acyl homoserine lactones (AHL) or cis-2-dodecenoic acid ("Burkholderia diffusible signal factor", BDSF) as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870), CciI (BCAM0239a) and the BDSF synthase (BCAM0581) were inactivated, and also constructed double (ΔcepIΔBCAM0581, ΔcciIΔBCAM0581 and ΔcepIΔcciI) mutants and a triple (ΔcepIΔcciIΔBCAM0581) mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans) and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The ΔBCAM0581 mutant and the ΔcepIΔBCAM0581 and ΔcciIΔBCAM0581 double mutants produced significantly less AHL compared to the WT strain and the ΔcepI and ΔcciI single mutant, respectively. The expression of cepI and cciI in ΔBCAM0581, was approximately 3-fold and 7-fold (p<0.05) lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the ΔBCAM0581 mutant could (at least partially) be restored by addition of BDSF. Our data suggest that, in B. cenocepacia J2315, AHL and BDSF-based QS systems co-regulate the same set of genes, regulate different sets of genes that are involved in the same phenotypes and/or that the BDSF system controls the AHL-based QS system. As the expression of the gene encoding the C6-HSL synthase CciI (and to a lesser extent

  10. Phenotypic and Genotypic Characterisation of Burkholderia cenocepacia J2315 Mutants Affected in Homoserine Lactone and Diffusible Signal Factor-Based Quorum Sensing Systems Suggests Interplay between Both Types of Systems

    PubMed Central

    Udine, Claudia; Brackman, Gilles; Bazzini, Silvia; Buroni, Silvia; Van Acker, Heleen; Pasca, Maria Rosalia; Riccardi, Giovanna; Coenye, Tom

    2013-01-01

    Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS) circuits. These QS systems either use N-acyl homoserine lactones (AHL) or cis-2-dodecenoic acid (“Burkholderia diffusible signal factor”, BDSF) as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870), CciI (BCAM0239a) and the BDSF synthase (BCAM0581) were inactivated, and also constructed double (ΔcepIΔBCAM0581, ΔcciIΔBCAM0581 and ΔcepIΔcciI) mutants and a triple (ΔcepIΔcciIΔBCAM0581) mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans) and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The ΔBCAM0581 mutant and the ΔcepIΔBCAM0581 and ΔcciIΔBCAM0581 double mutants produced significantly less AHL compared to the WT strain and the ΔcepI and ΔcciI single mutant, respectively. The expression of cepI and cciI in ΔBCAM0581, was approximately 3-fold and 7-fold (p<0.05) lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the ΔBCAM0581 mutant could (at least partially) be restored by addition of BDSF. Our data suggest that, in B. cenocepacia J2315, AHL and BDSF-based QS systems co-regulate the same set of genes, regulate different sets of genes that are involved in the same phenotypes and/or that the BDSF system controls the AHL-based QS system. As the expression of the gene encoding the C6-HSL synthase CciI (and to a lesser

  11. A genetically engineered whole-cell pigment-based bacterial biosensing system for quantification of N-butyryl homoserine lactone quorum sensing signal.

    PubMed

    Yong, Yang-Chun; Zhong, Jian-Jiang

    2009-09-15

    N-acyl homoserine lactone (AHL) is a widely conserved quorum sensing (QS) signal of gram-negative bacteria and has received attention in fighting against human diseases and environmental pollution. However, a method for quantifying AHL is lacking although it is urgently required for diagnosis and bioprocess manipulation. This work screened out an aromatics degrader Pseudomonas aeruginosa for biosensing system development, which produced a blue-green pigment regulated by the RhlI-RhlR QS system. By taking advantage of the recognition of N-butyryl homoserine lactone (BHL, the signal molecule of RhlI-RhlR QS system and an AHL) by the product of rhlR, a new whole-cell biosensor P. aeruginosa Delta rhlIR/pYC-rhlR (rhlI(-)rhlR(++)) was developed. It was constructed through abolishing its BHL production by in-frame deletion of rhlIR and over-expressing rhlR by introducing a multi-copy plasmid pYC-rhlR into Delta rhlIR. By using the pigment production which responded to exogenous BHL as biosensor output, BHL quantification in samples was simply done spectrophotometrically. Under optimum conditions, the calibration curve had the limit of detection (LOD), the 50% activation/effect concentration, the limit of quantification (LOQ), and the quantitative detection range of 1.3 nM, 2.77+/-0.45 microM, 5.7 nM and 0.11-49.7 microM, respectively. The biosensor output was stable, culture samples could be stored 10 days under -20 degrees C, and this sensing system was resistant to interferences by toxic aromatic pollutants. It was successfully applied to environmental samples even without extraction. The new whole-cell biosensing system provided a simple, stable, toxic pollutants-tolerant, and cost-effective tool for quantitative investigation of the QS signals' role in environmental processes.

  12. Maintenance of Paraoxonase 2 Activity as a Strategy to Attenuate P. Aeruginosa Virulence

    DTIC Science & Technology

    2015-12-01

    host immune responses and acquire antibiotic resistance (4). Many gram -negative bacteria, including Pa, produce acyl-homoserine lactone (AHL...Sarstedt). The next day, cells 17 were gently washed with HBSS, stained with 5 µM 5-(and-6)-carboxy SNARF ® -1 acetoxymethyl ester, acetate...adjusted to pH 7.5 with Tris) for 3 h to allow mitochondrial targeting of SNARF-1. During a further 15 min incubation time cells were stained in HBSS

  13. A new role for penicillin acylases: degradation of acyl homoserine lactone quorum sensing signals by Kluyvera citrophila penicillin G acylase.

    PubMed

    Mukherji, Ruchira; Varshney, Nishant Kumar; Panigrahi, Priyabrata; Suresh, C G; Prabhune, Asmita

    2014-03-05

    Use of penicillin acylases for the production of semi-synthetic penicillins is well-known. Escherichia coli penicillin G acylase (EcPGA) has been extensively used for this purpose; however, Kluyvera citrophila penicillin G acylase (KcPGA) is assumed to be a better substitute, owing to its increased resilience to extreme pH conditions and ease of immobilization. In the present article we report a new dimension for the amidase activity of KcPGA by demonstrating its ability to cleave bacterial quorum sensing signal molecules, acyl homoserine lactones (AHL) with acyl chain length of 6-8 with or without oxo-substitution at third carbon position. Initial evidence of AHL degrading capability of KcPGA was obtained using CV026 based bioassay method. Kinetic studies performed at pH 8.0 and 50 °C revealed 3-oxo-C6 HSL to be the best substrate for the enzyme with V(max) and K(m) values of 21.37+0.85 mM/h/mg of protein and 0.1+0.01 mM, respectively. C6 HSL was found to be the second best substrate with V(max) and K(m) value of 10.06+0.27 mM/h/mg of protein and 0.28+0.02 mM, respectively. Molecular modeling and docking studies performed on the active site of the enzyme support these findings by showing the fitting of AHLs perfectly within the hydrophobic pocket of the enzyme active site. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. Commonalities and differences in regulation of N-acyl homoserine lactone quorum sensing in the beneficial plant-associated burkholderia species cluster.

    PubMed

    Suárez-Moreno, Zulma Rocío; Devescovi, Giulia; Myers, Mike; Hallack, Letícia; Mendonça-Previato, Lucia; Caballero-Mellado, Jesús; Venturi, Vittorio

    2010-07-01

    The genus Burkholderia includes over 60 species isolated from a wide range of environmental niches and can be tentatively divided into two major species clusters. The first cluster includes pathogens such as Burkholderia glumae, B. pseudomallei, and B. mallei and 17 well-studied species of the Burkholderia cepacia complex. The other recently established cluster comprises at least 29 nonpathogenic species, which in most cases have been found to be associated with plants. It was previously established that Burkholderia kururiensis, a member of the latter cluster, possesses an N-acyl homoserine lactone (AHL) quorum-sensing (QS) system designated "BraI/R," which is found in all species of the plant-associated cluster. In the present study, two other BraI/R-like systems were characterized in B. xenovorans and B. unamae and were designated the BraI/R(XEN) and BraI/R(UNA) systems, respectively. Several phenotypes were analyzed, and it was determined that exopolysaccharide was positively regulated by the BraIR-like system in the species B. kururiensis, B. unamae, and B. xenovorans, highlighting commonality in targets. However, the three BraIR-like systems also revealed differences in targets since biofilm formation and plant colonization were differentially regulated. In addition, a second AHL QS system designated XenI2/R2 and an unpaired LuxR solo protein designated BxeR solo were also identified and characterized in B. xenovorans LB400(T). The two AHL QS systems of B. xenovorans are not transcriptionally regulating each other, whereas BxeR solo negatively regulated xenI2. The XenI2/R2 and BxeR solo proteins are not widespread in the Burkholderia species cluster. In conclusion, the present study represents an extensive analysis of AHL QS in the Burkholderia plant-associated cluster demonstrating both commonalities and differences, probably reflecting environmental adaptations of the various species.

  15. Commonalities and Differences in Regulation of N-Acyl Homoserine Lactone Quorum Sensing in the Beneficial Plant-Associated Burkholderia Species Cluster▿ †

    PubMed Central

    Suárez-Moreno, Zulma Rocío; Devescovi, Giulia; Myers, Mike; Hallack, Letícia; Mendonça-Previato, Lucia; Caballero-Mellado, Jesús; Venturi, Vittorio

    2010-01-01

    The genus Burkholderia includes over 60 species isolated from a wide range of environmental niches and can be tentatively divided into two major species clusters. The first cluster includes pathogens such as Burkholderia glumae, B. pseudomallei, and B. mallei and 17 well-studied species of the Burkholderia cepacia complex. The other recently established cluster comprises at least 29 nonpathogenic species, which in most cases have been found to be associated with plants. It was previously established that Burkholderia kururiensis, a member of the latter cluster, possesses an N-acyl homoserine lactone (AHL) quorum-sensing (QS) system designated “BraI/R,” which is found in all species of the plant-associated cluster. In the present study, two other BraI/R-like systems were characterized in B. xenovorans and B. unamae and were designated the BraI/RXEN and BraI/RUNA systems, respectively. Several phenotypes were analyzed, and it was determined that exopolysaccharide was positively regulated by the BraIR-like system in the species B. kururiensis, B. unamae, and B. xenovorans, highlighting commonality in targets. However, the three BraIR-like systems also revealed differences in targets since biofilm formation and plant colonization were differentially regulated. In addition, a second AHL QS system designated XenI2/R2 and an unpaired LuxR solo protein designated BxeR solo were also identified and characterized in B. xenovorans LB400T. The two AHL QS systems of B. xenovorans are not transcriptionally regulating each other, whereas BxeR solo negatively regulated xenI2. The XenI2/R2 and BxeR solo proteins are not widespread in the Burkholderia species cluster. In conclusion, the present study represents an extensive analysis of AHL QS in the Burkholderia plant-associated cluster demonstrating both commonalities and differences, probably reflecting environmental adaptations of the various species. PMID:20435760

  16. Genome sequencing-assisted identification and the first functional validation of N-acyl-homoserine-lactone synthases from the Sphingomonadaceae family

    PubMed Central

    Gan, Han Ming; Dailey, Lucas K.; Halliday, Nigel; Williams, Paul; Hudson, André O.

    2016-01-01

    Background Members of the genus Novosphingobium have been isolated from a variety of environmental niches. Although genomics analyses have suggested the presence of genes associated with quorum sensing signal production e.g., the N-acyl-homoserine lactone (AHL) synthase (luxI) homologs in various Novosphingobium species, to date, no luxI homologs have been experimentally validated. Methods In this study, we report the draft genome of the N-(AHL)-producing bacterium Novosphingobium subterraneum DSM 12447 and validate the functions of predicted luxI homologs from the bacterium through inducible heterologous expression in Agrobacterium tumefaciens strain NTL4. We developed a two-dimensional thin layer chromatography bioassay and used LC-ESI MS/MS analyses to separate, detect and identify the AHL signals produced by the N. subterraneum DSM 12447 strain. Results Three predicted luxI homologs were annotated to the locus tags NJ75_2841 (NovINsub1), NJ75_2498 (NovINsub2), and NJ75_4146 (NovINsub3). Inducible heterologous expression of each luxI homologs followed by LC-ESI MS/MS and two-dimensional reverse phase thin layer chromatography bioassays followed by bioluminescent ccd camera imaging indicate that the three LuxI homologs are able to produce a variety of medium-length AHL compounds. New insights into the LuxI phylogeny was also gleemed as inferred by Bayesian inference. Discussion This study significantly adds to our current understanding of quorum sensing in the genus Novosphingobium and provide the framework for future characterization of the phylogenetically interesting LuxI homologs from members of the genus Novosphingobium and more generally the family Sphingomonadaceae. PMID:27635318

  17. Sesquiterpenoids lactones: benefits to plants and people.

    PubMed

    Chadwick, Martin; Trewin, Harriet; Gawthrop, Frances; Wagstaff, Carol

    2013-06-19

    Sesquiterpenoids, and specifically sesquiterpene lactones from Asteraceae, may play a highly significant role in human health, both as part of a balanced diet and as pharmaceutical agents, due to their potential for the treatment of cardiovascular disease and cancer. This review highlights the role of sesquiterpene lactones endogenously in the plants that produce them, and explores mechanisms by which they interact in animal and human consumers of these plants. Several mechanisms are proposed for the reduction of inflammation and tumorigenesis at potentially achievable levels in humans. Plants can be classified by their specific array of produced sesquiterpene lactones, showing high levels of translational control. Studies of folk medicines implicate sesquiterpene lactones as the active ingredient in many treatments for other ailments such as diarrhea, burns, influenza, and neurodegradation. In addition to the anti-inflammatory response, sesquiterpene lactones have been found to sensitize tumor cells to conventional drug treatments. This review explores the varied ecological roles of sesquiterpenes in the plant producer, depending upon the plant and the compound. These include allelopathy with other plants, insects, and microbes, thereby causing behavioural or developmental modification to these secondary organisms to the benefit of the sesquiterpenoid producer. Some sesquiterpenoid lactones are antimicrobial, disrupting the cell wall of fungi and invasive bacteria, whereas others protect the plant from environmental stresses that would otherwise cause oxidative damage. Many of the compounds are effective due to their bitter flavor, which has obvious implications for human consumers. The implications of sesquiterpenoid lactone qualities for future crop production are discussed.

  18. Sesquiterpenoids Lactones: Benefits to Plants and People

    PubMed Central

    Chadwick, Martin; Trewin, Harriet; Gawthrop, Frances; Wagstaff, Carol

    2013-01-01

    Sesquiterpenoids, and specifically sesquiterpene lactones from Asteraceae, may play a highly significant role in human health, both as part of a balanced diet and as pharmaceutical agents, due to their potential for the treatment of cardiovascular disease and cancer. This review highlights the role of sesquiterpene lactones endogenously in the plants that produce them, and explores mechanisms by which they interact in animal and human consumers of these plants. Several mechanisms are proposed for the reduction of inflammation and tumorigenesis at potentially achievable levels in humans. Plants can be classified by their specific array of produced sesquiterpene lactones, showing high levels of translational control. Studies of folk medicines implicate sesquiterpene lactones as the active ingredient in many treatments for other ailments such as diarrhea, burns, influenza, and neurodegradation. In addition to the anti-inflammatory response, sesquiterpene lactones have been found to sensitize tumor cells to conventional drug treatments. This review explores the varied ecological roles of sesquiterpenes in the plant producer, depending upon the plant and the compound. These include allelopathy with other plants, insects, and microbes, thereby causing behavioural or developmental modification to these secondary organisms to the benefit of the sesquiterpenoid producer. Some sesquiterpenoid lactones are antimicrobial, disrupting the cell wall of fungi and invasive bacteria, whereas others protect the plant from environmental stresses that would otherwise cause oxidative damage. Many of the compounds are effective due to their bitter flavor, which has obvious implications for human consumers. The implications of sesquiterpenoid lactone qualities for future crop production are discussed. PMID:23783276

  19. Synthesis and Biological Evaluation of Triazole-Containing N-Acyl Homoserine Lactones as Quorum Sensing Modulators

    PubMed Central

    Stacy, Danielle M.; Le Quement, Sebastian T.; Hansen, Casper L.; Clausen, Janie W.; Tolker-Nielsen, Tim; Brummond, Jacob W.; Givskov, Michael; Nielsen, Thomas E.; Blackwell, Helen E.

    2013-01-01

    Many bacterial species are capable of assessing their local population densities through a cell-cell signaling mechanism termed quorum sensing (QS). This intercellular communication process is mediated by small molecule or peptide ligands and their cognate protein receptors. Numerous pathogens use QS to initiate virulence once they achieve a threshold cell number on a host. Consequently, approaches to intercept QS have attracted considerable attention as potential anti-infective therapies. Our interest in the development of small molecule tools to modulate QS pathways motivated us to evaluate triazole-containing analogs of natural N-acyl L-homoserine lactone (AHL) signals as non-native QS agonists and antagonists in Gram-negative bacteria. We synthesized 72 triazole derivatives of five broad structure types in high yields and purities using efficient Cu(I)-catalyzed azide-alkyne couplings. These compounds were evaluated for their ability to activate or inhibit two QS receptors from two prevalent pathogens – LasR from Pseudomonas aeruginosa and AbaR from Acinetobacter baumannii – using bacterial reporter strains. Several triazole derivatives were identified that were capable of strongly modulating the activity of LasR and AbaR. These compounds represent a new and synthetically accessible class of AHL analogs, and could find utility as chemical tools to study QS and its role in bacterial virulence. PMID:23258305

  20. A New N-Acyl Homoserine Lactone Synthase in an Uncultured Symbiont of the Red Sea Sponge Theonella swinhoei

    PubMed Central

    Britstein, Maya; Devescovi, Giulia; Handley, Kim M.; Malik, Assaf; Haber, Markus; Saurav, Kumar; Teta, Roberta; Costantino, Valeria; Burgsdorf, Ilia; Gilbert, Jack A.; Sher, Noa; Venturi, Vittorio

    2015-01-01

    Sponges harbor a remarkable diversity of microbial symbionts in which signal molecules can accumulate and enable cell-cell communication, such as quorum sensing (QS). Bacteria capable of QS were isolated from marine sponges; however, an extremely small fraction of the sponge microbiome is amenable to cultivation. We took advantage of community genome assembly and binning to investigate the uncultured majority of sponge symbionts. We identified a complete N-acyl-homoserine lactone (AHL)-QS system (designated TswIR) and seven partial luxI homologues in the microbiome of Theonella swinhoei. The TswIR system was novel and shown to be associated with an alphaproteobacterium of the order Rhodobacterales, here termed Rhodobacterales bacterium TS309. The tswI gene, when expressed in Escherichia coli, produced three AHLs, two of which were also identified in a T. swinhoei sponge extract. The taxonomic affiliation of the 16S rRNA of Rhodobacterales bacterium TS309 to a sponge-coral specific clade, its enrichment in sponge versus seawater and marine sediment samples, and the presence of sponge-specific features, such as ankyrin-like domains and tetratricopeptide repeats, indicate a likely symbiotic nature of this bacterium. PMID:26655754

  1. Use of aiiA gene amplification for AHL-lactonase production from endophytic bacterium Enterobacter species.

    PubMed

    Rajesh, P S; Rai, V Ravishankar

    2015-01-01

    AHL-lactonase has gained renewed interest due to biotechnological applications such as antiquorum sensing, antibiofilm strategies, biofouling, etc. In our study, the production of AHL-lactonase from endophytic bacteria Enterobacter aerogenes VT66 was optimized by response surface methodology (RSM) using central composite design (CCD) for four different cultural conditions. The relative activity of AHL-lactonase was correlated with amplification of aiiA homologous gene amplification with respect to cultural conditions. Statistical analysis by ANOVA of the quadratic regression model showed that the RSM model constructed is highly significant, as indicated by F-test with a low probability value (p(model) < 0.0001) and high regression coefficient (0.9997) as well as lower coefficient of variation (1.86%) indicate that suitability of variable parameters. The quadratic regression model of AHL-lactonase production in terms of relative activity was built and the optimal cultural conditions for maximum enzyme production were determined as 32.5 °C temperature, pH 7.0, 350 μM of substrate concentration and 33 h of incubation time. The enhanced AHL-lactonase yielded 1.33 fold increases in relative activity and it positively correlated with the amplification of aiiA gene.

  2. Paraoxonase 2 modulates a proapoptotic function in LS174T cells in response to quorum sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone.

    PubMed

    Tao, Shiyu; Luo, Yanwen; Bin He; Liu, Jie; Qian, Xi; Ni, Yingdong; Zhao, Ruqian

    2016-07-01

    A mucus layer coats the gastrointestinal tract and serves as the first line of intestinal defense against infection. N-acyl-homoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence the homeostasis of intestinal epithelium. In this study, we investigated the effects of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on cell viability and mucus secretion in LS174T cells. C12-HSL but not C4-HSL significantly decreased cell viability by inducing mitochondrial dysfunction and activating cell apoptosis which led to a decrease in mucin expression. Pretreatment with lipid raft disruptor (Methyl-β-cyclodextrin, MβCD) and oxidative stress inhibitor (N-acetyl-L-cysteine, NAC) slightly rescued the viability of cells damaged by C12-HSL exposure, while the paraoxonase 2 (PON2) inhibitor (Triazolo[4,3-a]quinolone, TQ416) significantly affected recovering cells viability and mucin secretion. When LS174T cells were treated with C12-HSL and TQ416 simultaneously, TQ416 showed the maximal positive effect on cells viability. However, if cells were first treated with C12-HSL for 40 mins, and then TQ46 was added, the TQ416 had no effect on cell viability. These results suggest that the C12-HSL-acid process acts at an early step to activate apoptosis as part of C12-HSL's effect on intestinal mucus barrier function.

  3. Paraoxonase 2 modulates a proapoptotic function in LS174T cells in response to quorum sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone

    PubMed Central

    Tao, Shiyu; Luo, Yanwen; Bin He; Liu, Jie; Qian, Xi; Ni, Yingdong; Zhao, Ruqian

    2016-01-01

    A mucus layer coats the gastrointestinal tract and serves as the first line of intestinal defense against infection. N-acyl-homoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence the homeostasis of intestinal epithelium. In this study, we investigated the effects of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on cell viability and mucus secretion in LS174T cells. C12-HSL but not C4-HSL significantly decreased cell viability by inducing mitochondrial dysfunction and activating cell apoptosis which led to a decrease in mucin expression. Pretreatment with lipid raft disruptor (Methyl-β-cyclodextrin, MβCD) and oxidative stress inhibitor (N-acetyl-L-cysteine, NAC) slightly rescued the viability of cells damaged by C12-HSL exposure, while the paraoxonase 2 (PON2) inhibitor (Triazolo[4,3-a]quinolone, TQ416) significantly affected recovering cells viability and mucin secretion. When LS174T cells were treated with C12-HSL and TQ416 simultaneously, TQ416 showed the maximal positive effect on cells viability. However, if cells were first treated with C12-HSL for 40 mins, and then TQ46 was added, the TQ416 had no effect on cell viability. These results suggest that the C12-HSL-acid process acts at an early step to activate apoptosis as part of C12-HSL’s effect on intestinal mucus barrier function. PMID:27364593

  4. The Fe(III) and Ga(III) coordination chemistry of 3-(1-hydroxymethylidene) and 3-(1-hydroxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4-dione: novel tetramic acid degradation products of homoserine lactone bacterial quorum sensing molecules.

    PubMed

    Romano, Ariel A; Hahn, Tobias; Davis, Nicole; Lowery, Colin A; Struss, Anjali K; Janda, Kim D; Böttger, Lars H; Matzanke, Berthold F; Carrano, Carl J

    2012-02-01

    Bacteria use small diffusible molecules to exchange information in a process called quorum sensing (QS). An important class of quorum sensing molecules used by Gram-negative bacteria is the family of N-acylhomoserine lactones (HSL). It was recently discovered that a degradation product of the QS molecule 3-oxo-C(12)-homoserine lactone, the tetramic acid 3-(1-hydroxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4-dione, is a potent antibacterial agent, thus implying roles for QS outside of simply communication. Because these tetramic acids also appear to bind iron with appreciable affinity it was suggested that metal binding might contribute to their biological activity. Here, using a variety of spectroscopic tools, we describe the coordination chemistry of both the methylidene and decylidene tetramic acid derivatives with Fe(III) and Ga(III) and discuss the potential biological significance of such metal binding.

  5. The Fe(III) and Ga(III) coordination chemistry of 3-(1-hydroxymethylidene) and 3-(1-hydroxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4-dione: Novel tetramic acid degradation products of homoserine lactone bacterial quorum sensing molecules

    PubMed Central

    Romano, Ariel A.; Hahn, Tobias; Davis, Nicole; Lowery, Colin A.; Struss, Anjali K.; Janda, Kim D.; Böttger, Lars H.; Matzanke, Berthold F.; Carrano, Carl J.

    2011-01-01

    Bacteria use small diffusible molecules to exchange information in a process called quorum sensing (QS). An important class of quorum sensing molecules used by Gram-negative bacteria is the family of N-acylhomoserine lactones (HSL). It was recently discovered that a degradation product of the QS molecule 3-oxo-C12-homoserine lactone, the tetramic acid 3-(1-hydroxydecylidene)-5-(2-hydroxyethyl)pyrrolidine-2,4-dione, is a potent antibacterial agent, thus implying roles for QS outside of simply communication. Because these tetramic acids also appear to bind iron with appreciable affinity it was suggested that metal binding might contribute to their biological activity. Here, using a variety of spectroscopic tools, we describe the coordination chemistry of both the methylidene and decylidene tetramic acid derivatives with Fe(III) and Ga(III) and discuss the potential biological significance of such metal binding. PMID:22178671

  6. Improved bioassay for detecting autoinducer of Rhodovulum sulfidophilum

    NASA Astrophysics Data System (ADS)

    Terada, T.; Kikuchi, Y.; Umekage, S.

    2015-02-01

    Quorum sensing is a bacterial gene regulation system that enables prompt environmental adaptation in response to cell density. Quorum sensing is driven by an extracellularly secreted chemical signal called autoinducer. Gram-negative bacteria produce one or several types of N-acylhomoserine lactone (AHL) as autoinducers. Our previous study suggests that the gram-negative marine photosynthetic bacterium Rhodovulum sulfidophilum produces AHL in the early stationary phase and plays a role in maintaining the bacterial cell aggregates called "floc". We performed conventional bioassay to identify AHL production by using Chromobacterium violaceum VIR07, which produces violet pigment (violacein) in response to AHL with side chains ranging from C10 to C18 in length. However, we were not able to observe the violacein with good reproducibility, suggesting that inhibitory chemical compounds co-existed in the AHL extract. Therefore, we improved the extraction method; the ethyl acetate-extracted AHLs were fractionated by using reverse phase TLC. By using the re-extracted AHLs for the bioassay, we observed an obvious production of violacein. This result clearly indicates that R. sulfidophilum produces AHLs with side chains ranging from C10 to C18 in length and suggests the utility of improved bioassay for AHL detection.

  7. Identification of sdiA-regulated genes in a mouse commensal strain of Enterobacter cloacae

    PubMed Central

    Sabag-Daigle, Anice; Dyszel, Jessica L.; Gonzalez, Juan F.; Ali, Mohamed M.; Ahmer, Brian M. M.

    2015-01-01

    Many bacteria determine their population density using quorum sensing. The most intensively studied mechanism of quorum sensing utilizes proteins of the LuxI family to synthesize a signaling molecule of the acylhomoserine lactone (AHL) type, and a protein of the LuxR family to bind AHL and regulate transcription. Genes regulated by quorum sensing often encode functions that are most effective when a group of bacteria are working cooperatively (e.g., luminescence, biofilm formation, host interactions). Bacteria in the Escherichia, Salmonella, Klebsiella, and Enterobacter genera do not encode an AHL synthase but they do encode an AHL receptor of the LuxR family, SdiA. Instead of detecting their own AHL synthesis, these organisms use SdiA to detect the AHLs synthesized by other bacterial species. In this study, we used a genetic screen to identify AHL-responsive genes in a commensal Enterobacter cloacae strain that was isolated from a laboratory mouse. The genes include a putative type VI secretion system, copA (a copper transporter), and fepE (extends O-antigen chain length). A new transposon mutagenesis strategy and suicide vectors were used to construct an sdiA mutant of E. cloacae. The AHL-responsiveness of all fusions was entirely sdiA-dependent, although some genes were regulated by sdiA in the absence of AHL. PMID:26075189

  8. Identification of sdiA-regulated genes in a mouse commensal strain of Enterobacter cloacae.

    PubMed

    Sabag-Daigle, Anice; Dyszel, Jessica L; Gonzalez, Juan F; Ali, Mohamed M; Ahmer, Brian M M

    2015-01-01

    Many bacteria determine their population density using quorum sensing. The most intensively studied mechanism of quorum sensing utilizes proteins of the LuxI family to synthesize a signaling molecule of the acylhomoserine lactone (AHL) type, and a protein of the LuxR family to bind AHL and regulate transcription. Genes regulated by quorum sensing often encode functions that are most effective when a group of bacteria are working cooperatively (e.g., luminescence, biofilm formation, host interactions). Bacteria in the Escherichia, Salmonella, Klebsiella, and Enterobacter genera do not encode an AHL synthase but they do encode an AHL receptor of the LuxR family, SdiA. Instead of detecting their own AHL synthesis, these organisms use SdiA to detect the AHLs synthesized by other bacterial species. In this study, we used a genetic screen to identify AHL-responsive genes in a commensal Enterobacter cloacae strain that was isolated from a laboratory mouse. The genes include a putative type VI secretion system, copA (a copper transporter), and fepE (extends O-antigen chain length). A new transposon mutagenesis strategy and suicide vectors were used to construct an sdiA mutant of E. cloacae. The AHL-responsiveness of all fusions was entirely sdiA-dependent, although some genes were regulated by sdiA in the absence of AHL.

  9. X-ray crystal structures of the pheromone-binding domains of two quorum-hindered transcription factors, YenR of Yersinia enterocolitica and CepR2 of Burkholderia cenocepacia.

    PubMed

    Kim, Youngchang; Chhor, Gekleng; Tsai, Ching-Sung; Fox, Gabriel; Chen, Chia-Sui; Winans, Nathan J; Jedrzejczak, Robert; Joachimiak, Andrzej; Winans, Stephen C

    2017-10-01

    The ability of LuxR-type proteins to regulate transcription is controlled by bacterial pheromones, N-acylhomoserine lactones (AHLs). Most LuxR-family proteins require their cognate AHLs for activity, and some of them require AHLs for folding and stability, and for protease-resistance. However, a few members of this family are able to fold, dimerize, bind DNA, and regulate transcription in the absence of AHLs; moreover, these proteins are antagonized by their cognate AHLs. One such protein is YenR of Yersinia enterocolitica, which is antagonized by N-3-oxohexanoyl-l-homoserine lactone (OHHL). This pheromone is produced by the OHHL synthase, a product of the adjacent yenI gene. Another example is CepR2 of Burkholderia cenocepacia, which is antagonized by N-octanoyl-l-homoserine lactone (OHL), whose synthesis is directed by the cepI gene of the same bacterium. Here, we describe the high-resolution crystal structures of the AHL binding domains of YenR and CepR2. YenR was crystallized in the presence and absence of OHHL. While this ligand does not cause large scale changes in the YenR structure, it does alter the orientation of several highly conserved YenR residues within and near the pheromone-binding pocket, which in turn caused a significant movement of a surface-exposed loop. © 2017 Wiley Periodicals, Inc.

  10. Identification of Quorum-Sensing Signal Molecules and a Biosynthetic Gene in Alicycliphilus sp. Isolated from Activated Sludge.

    PubMed

    Morohoshi, Tomohiro; Okutsu, Noriya; Xie, Xiaonan; Ikeda, Tsukasa

    2016-08-02

    Activated sludge is a complicated mixture of various microorganisms that is used to treat sewage and industrial wastewater. Many bacteria produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule to regulate the expression of the exoenzymes used for wastewater treatment. Here, we isolated an AHL-producing bacteria from an activated sludge sample collected from an electronic component factory, which we named Alicycliphilus sp. B1. Clone library analysis revealed that Alicycliphilus was a subdominant genus in this sample. When we screened the activated sludge sample for AHL-producing strains, 12 of 14 the AHL-producing isolates were assigned to the genus Alicycliphilus. A putative AHL-synthase gene, ALISP_0667, was cloned from the genome of B1 and transformed into Escherichia coli DH5α. The AHLs were extracted from the culture supernatants of the B1 strain and E. coli DH5α cells harboring the ALISP_0667 gene and were identified by liquid chromatography-mass spectrometry as N-(3-hydroxydecanoyl)-l-homoserine lactone and N-(3-hydroxydodecanoyl)-l-homoserine lactone. The results of comparative genomic analysis suggested that the quorum-sensing genes in the B1 strain might have been acquired by horizontal gene transfer within activated sludge.

  11. Identification of Quorum-Sensing Signal Molecules and a Biosynthetic Gene in Alicycliphilus sp. Isolated from Activated Sludge

    PubMed Central

    Morohoshi, Tomohiro; Okutsu, Noriya; Xie, Xiaonan; Ikeda, Tsukasa

    2016-01-01

    Activated sludge is a complicated mixture of various microorganisms that is used to treat sewage and industrial wastewater. Many bacteria produce N-acylhomoserine lactone (AHL) as a quorum-sensing signal molecule to regulate the expression of the exoenzymes used for wastewater treatment. Here, we isolated an AHL-producing bacteria from an activated sludge sample collected from an electronic component factory, which we named Alicycliphilus sp. B1. Clone library analysis revealed that Alicycliphilus was a subdominant genus in this sample. When we screened the activated sludge sample for AHL-producing strains, 12 of 14 the AHL-producing isolates were assigned to the genus Alicycliphilus. A putative AHL-synthase gene, ALISP_0667, was cloned from the genome of B1 and transformed into Escherichia coli DH5α. The AHLs were extracted from the culture supernatants of the B1 strain and E. coli DH5α cells harboring the ALISP_0667 gene and were identified by liquid chromatography-mass spectrometry as N-(3-hydroxydecanoyl)-l-homoserine lactone and N-(3-hydroxydodecanoyl)-l-homoserine lactone. The results of comparative genomic analysis suggested that the quorum-sensing genes in the B1 strain might have been acquired by horizontal gene transfer within activated sludge. PMID:27490553

  12. Homoserine and quorum-sensing acyl homoserine lactones as alternative sources of threonine: a potential role for homoserine kinase in insect-stage Trypanosoma brucei

    PubMed Central

    Ong, Han B; Lee, Wai S; Patterson, Stephen; Wyllie, Susan; Fairlamb, Alan H

    2015-01-01

    De novo synthesis of threonine from aspartate occurs via the β-aspartyl phosphate pathway in plants, bacteria and fungi. However, the Trypanosoma brucei genome encodes only the last two steps in this pathway: homoserine kinase (HSK) and threonine synthase. Here, we investigated the possible roles for this incomplete pathway through biochemical, genetic and nutritional studies. Purified recombinant TbHSK specifically phosphorylates L-homoserine and displays kinetic properties similar to other HSKs. HSK null mutants generated in bloodstream forms displayed no growth phenotype in vitro or loss of virulence in vivo. However, following transformation into procyclic forms, homoserine, homoserine lactone and certain acyl homoserine lactones (AHLs) were found to substitute for threonine in growth media for wild-type procyclics, but not HSK null mutants. The tsetse fly is considered to be an unlikely source of these nutrients as it feeds exclusively on mammalian blood. Bioinformatic studies predict that tsetse endosymbionts possess part (up to homoserine in Wigglesworthia glossinidia) or all of the β-aspartyl phosphate pathway (Sodalis glossinidius). In addition S. glossinidius is known to produce 3-oxohexanoylhomoserine lactone which also supports trypanosome growth. We propose that T. brucei has retained HSK and threonine synthase in order to salvage these nutrients when threonine availability is limiting. PMID:25367138

  13. Mechanisms of lactone hydrolysis in acidic conditions.

    PubMed

    Gómez-Bombarelli, Rafael; Calle, Emilio; Casado, Julio

    2013-07-19

    The acid-catalyzed hydrolysis of linear esters and lactones was studied using a hybrid supermolecule-polarizable continuum model (PCM) approach including up to six water molecules. The compounds studied included two linear esters, four β-lactones, two γ-lactones, and one δ-lactone: ethyl acetate, methyl formate, β-propiolactone, β-butyrolactone, β-isovalerolactone, diketene (4-methyleneoxetan-2-one), γ-butyrolactone, 2(5H)-furanone, and δ-valerolactone. The theoretical results are in good quantitative agreement with the experimental measurements reported in the literature and also in excellent qualitative agreement with long-held views regarding the nature of the hydrolysis mechanisms at molecular level. The present results help to understand the balance between the unimolecular (A(AC)1) and bimolecular (A(AC)2) reaction pathways. In contrast to the experimental setting, where one of the two branches is often occluded by the requirement of rather extreme experimental conditions, we have been able to estimate both contributions for all the compounds studied and found that a transition from A(AC)2 to A(AC)1 hydrolysis takes place as acidity increases. A parallel work addresses the neutral and base-catalyzed hydrolysis of lactones.

  14. Draft Genome Sequence of Pantoea sp. Strain A4, a Rafflesia-Associated Bacterium That Produces N-Acylhomoserine Lactones as Quorum-Sensing Molecules

    PubMed Central

    Hong, Kar-Wai; Gan, Han Ming; Low, Siew-Moon; Lee, Patrick Kok Yuen; Chong, Yee-Meng; Yin, Wai-Fong

    2012-01-01

    Pantoea sp. strain A4 is a Gram-negative bacterium isolated from the Rafflesia flower. We present here, for the first time, the genome sequence of Rafflesia-associated Pantoea sp. strain A4, which exhibited quorum-sensing activity. PMID:23144374

  15. Draft genome sequence of Pantoea sp. strain A4, a Rafflesia-associated bacterium that produces N-acylhomoserine lactones as quorum-sensing molecules.

    PubMed

    Hong, Kar-Wai; Gan, Han Ming; Low, Siew-Moon; Lee, Patrick Kok Yuen; Chong, Yee-Meng; Yin, Wai-Fong; Chan, Kok-Gan

    2012-12-01

    Pantoea sp. strain A4 is a Gram-negative bacterium isolated from the Rafflesia flower. We present here, for the first time, the genome sequence of Rafflesia-associated Pantoea sp. strain A4, which exhibited quorum-sensing activity.

  16. Acute human toxicity of macrocyclic lactones.

    PubMed

    Yang, Chen-Chang

    2012-05-01

    Macrocyclic lactones, including avermectins and milbemycins, are novel parasiticides and insecticides that are produced through fermentation by soil-dwelling microorganisms. Although various macrocyclic lactones may differ in their potency and safety, all of them are believed to share common pharmacologic/toxicologic mechanisms, i.e. leading to paralysis and death of parasites and other target organisms via the activation of a glutamate-gated chloride channel in the invertebrate nerve and muscle cells and/or through the effect on gamma-aminobutyric acid (GABA) receptors. Ivermectin is the first macrocyclic lactone that was released for use in both animals and humans, and has demonstrated both excellent efficacy and high tolerability in the treatment of parasite infestations. Other macrocyclic lactones, such as abamectin, emamectin, and moxidectin were subsequently commercialized and have been used as insecticides and acaricides for crop protection or parasiticides for animal health. Although ivermectin therapy is generally well tolerated, adverse effects that are usually transient and mild-to-moderate can occur. Severe adverse effects are rare and can generally be effectively controlled by symptomatic measures. Non-therapeutic exposures to ivermectin and other macrocyclic lactones may also result in toxic effects; significant toxicity however probably develops only after large amount of oral ingestion. Although the exact mechanisms remain unclear, macrocyclic lactones in large doses may pass through the blood-brain barrier (BBB) to produce GABA-mimetic toxic effects. Severely poisoned patients usually present with coma, hypotension, respiratory failure, and even death. Despite the lack of specific therapy, the prognosis is likely to be favorable unless the poisoned patients are complicated with severe hypotension or respiratory failure.

  17. Abietane lactones and iridoids from Goldfussia yunnanensis.

    PubMed

    Yu, Hong-Wei; Li, Bo-Gang; Li, Guo-You; Li, Chang-Song; Fang, Dong-Mei; Zhang, Guo-Lin

    2007-12-01

    Two new abietane diterpene lactones (1--2), three new abietane diterpene lactone glycosides (3--5) and a new iridoid glycoside (6), together with five known compounds, were isolated from the aerial parts of Goldfussia yunnanensis. The new compounds were determined to be 18-hydroxyhelioscopinolide A (1), 18-oxohelioscopinolide A (2), 18-hydroxy-3-O-beta-D-glucopyranosylhelioscopinolide A (3), 3-O-beta-D-glucopyranosylhelioscopinolide A (4), 3-O-beta-D-galactopyranosylhelioscopinolide A (5), and 6-O-trans-cinnamoyl E-harpagoside (6) on the basis of spectral data and chemical evidence.

  18. Galactaro δ-Lactone Isomerase: Lactone Isomerization by a Member of the Amidohydrolase Superfamily

    PubMed Central

    2015-01-01

    Agrobacterium tumefaciens strain C58 can utilize d-galacturonate as a sole source of carbon via a pathway in which the first step is oxidation of d-galacturonate to d-galactaro-1,5-lactone. We have identified a novel enzyme, d-galactarolactone isomerase (GLI), that catalyzes the isomerizaton of d-galactaro-1,5-lactone to d-galactaro-1,4-lactone. GLI, a member of the functionally diverse amidohydrolase superfamily, is a homologue of LigI that catalyzes the hydrolysis of 2-pyrone-4,6-dicarboxylate in lignin degradation. The ability of GLI to catalyze lactone isomerization instead of hydrolysis can be explained by the absence of the general basic catalysis used by 2-pyrone-4,6-dicarboxylate lactonase. PMID:24450804

  19. Galactaro δ-lactone isomerase: lactone isomerization by a member of the amidohydrolase superfamily.

    PubMed

    Bouvier, Jason T; Groninger-Poe, Fiona P; Vetting, Matthew; Almo, Steven C; Gerlt, John A

    2014-02-04

    Agrobacterium tumefaciens strain C58 can utilize d-galacturonate as a sole source of carbon via a pathway in which the first step is oxidation of d-galacturonate to D-galactaro-1,5-lactone. We have identified a novel enzyme, D-galactarolactone isomerase (GLI), that catalyzes the isomerizaton of D-galactaro-1,5-lactone to D-galactaro-1,4-lactone. GLI, a member of the functionally diverse amidohydrolase superfamily, is a homologue of LigI that catalyzes the hydrolysis of 2-pyrone-4,6-dicarboxylate in lignin degradation. The ability of GLI to catalyze lactone isomerization instead of hydrolysis can be explained by the absence of the general basic catalysis used by 2-pyrone-4,6-dicarboxylate lactonase.

  20. Lactones: Part 11. Feeding-deterrent activity of some bi- and tricyclic terpenoid lactones.

    PubMed

    Paruch, E; Nawrot, J; Wawrzeńczyk, C

    2001-09-01

    The feeding-deterrent activities of thirteen synthetic terpenoid lactones, including isomeric bicyclic gamma-spirolactones with the limonene system and tricyclic gamma-lactones with the pinane system, were determined towards three storage pest insects: the adults of Sitophilus granarius, the adults and larvae of Tribolium confusum and the larvae of Trogoderma granarium. The configuration of chiral centres, as well as the presence of additional functional groups (double bond, iodine and hydroxy group) are important for antifeeding activity.

  1. Aryl-homoserine lactone quorum sensing in stem-nodulating photosynthetic bradyrhizobia.

    PubMed

    Ahlgren, Nathan A; Harwood, Caroline S; Schaefer, Amy L; Giraud, Eric; Greenberg, E Peter

    2011-04-26

    Many Proteobacteria possess LuxI-LuxR-type quorum-sensing systems that produce and detect fatty acyl-homoserine lactone (HSL) signals. The photoheterotroph Rhodopseudomonas palustris is unusual in that it produces and detects an aryl-HSL, p-coumaroyl-HSL, and signal production requires an exogenous source of p-coumarate. A photosynthetic stem-nodulating member of the genus Bradyrhizobium produces a small molecule signal that elicits an R. palustris quorum-sensing response. Here, we show that this signal is cinnamoyl-HSL and that cinnamoyl-HSL is produced by the LuxI homolog BraI and detected by BraR. Cinnamoyl-HSL reaches concentrations on the order of 50 nM in cultures of stem-nodulating bradyrhizobia grown in the presence or absence of cinnamate. Acyl-HSLs often reach concentrations of 0.1-30 μM in bacterial cultures, and generally, LuxR-type receptors respond to signals in a concentration range from 5 to a few hundred nanomolar. Our stem-nodulating Bradyrhizobium strain responds to picomolar concentrations of cinnamoyl-HSL and thus, produces cinnamoyl-HSL in excess of the levels required for a signal response without an exogenous source of cinnamate. The ability of Bradyrhizobium to produce and respond to cinnamoyl-HSL shows that aryl-HSL production is not unique to R. palustris, that the aromatic acid substrate for aryl-HSL synthesis does not have to be supplied exogenously, and that some acyl-HSL quorum-sensing systems may function at very low signal production and response levels.

  2. Aryl-homoserine lactone quorum sensing in stem-nodulating photosynthetic bradyrhizobia

    PubMed Central

    Ahlgren, Nathan A.; Harwood, Caroline S.; Schaefer, Amy L.; Giraud, Eric; Greenberg, E. Peter

    2011-01-01

    Many Proteobacteria possess LuxI-LuxR–type quorum-sensing systems that produce and detect fatty acyl-homoserine lactone (HSL) signals. The photoheterotroph Rhodopseudomonas palustris is unusual in that it produces and detects an aryl-HSL, p-coumaroyl-HSL, and signal production requires an exogenous source of p-coumarate. A photosynthetic stem-nodulating member of the genus Bradyrhizobium produces a small molecule signal that elicits an R. palustris quorum-sensing response. Here, we show that this signal is cinnamoyl-HSL and that cinnamoyl-HSL is produced by the LuxI homolog BraI and detected by BraR. Cinnamoyl-HSL reaches concentrations on the order of 50 nM in cultures of stem-nodulating bradyrhizobia grown in the presence or absence of cinnamate. Acyl-HSLs often reach concentrations of 0.1–30 μM in bacterial cultures, and generally, LuxR-type receptors respond to signals in a concentration range from 5 to a few hundred nanomolar. Our stem-nodulating Bradyrhizobium strain responds to picomolar concentrations of cinnamoyl-HSL and thus, produces cinnamoyl-HSL in excess of the levels required for a signal response without an exogenous source of cinnamate. The ability of Bradyrhizobium to produce and respond to cinnamoyl-HSL shows that aryl-HSL production is not unique to R. palustris, that the aromatic acid substrate for aryl-HSL synthesis does not have to be supplied exogenously, and that some acyl-HSL quorum-sensing systems may function at very low signal production and response levels. PMID:21471459

  3. Insights into the Quorum Sensing Regulon of the Acidophilic Acidithiobacillus ferrooxidans Revealed by Transcriptomic in the Presence of an Acyl Homoserine Lactone Superagonist Analog.

    PubMed

    Mamani, Sigde; Moinier, Danielle; Denis, Yann; Soulère, Laurent; Queneau, Yves; Talla, Emmanuel; Bonnefoy, Violaine; Guiliani, Nicolas

    2016-01-01

    While a functional quorum sensing system has been identified in the acidophilic chemolithoautotrophic Acidithiobacillus ferrooxidans ATCC 23270(T) and shown to modulate cell adhesion to solid substrates, nothing is known about the genes it regulates. To address the question of how quorum sensing controls biofilm formation in A. ferrooxidans (T), the transcriptome of this organism in conditions in which quorum sensing response is stimulated by a synthetic superagonist AHL (N-acyl homoserine lactones) analog has been studied. First, the effect on biofilm formation of a synthetic AHL tetrazolic analog, tetrazole 9c, known for its agonistic QS activity, was assessed by fluorescence and electron microscopy. A fast adherence of A. ferrooxidans (T) cells on sulfur coupons was observed. Then, tetrazole 9c was used in DNA microarray experiments that allowed the identification of genes regulated by quorum sensing signaling, and more particularly, those involved in early biofilm formation. Interestingly, afeI gene, encoding the AHL synthase, but not the A. ferrooxidans quorum sensing transcriptional regulator AfeR encoding gene, was shown to be regulated by quorum sensing. Data indicated that quorum sensing network represents at least 4.5% (141 genes) of the ATCC 23270(T) genome of which 42.5% (60 genes) are related to biofilm formation. Finally, AfeR was shown to bind specifically to the regulatory region of the afeI gene at the level of the palindromic sequence predicted to be the AfeR binding site. Our results give new insights on the response of A. ferrooxidans to quorum sensing and on biofilm biogenesis.

  4. Insights into the Quorum Sensing Regulon of the Acidophilic Acidithiobacillus ferrooxidans Revealed by Transcriptomic in the Presence of an Acyl Homoserine Lactone Superagonist Analog

    PubMed Central

    Mamani, Sigde; Moinier, Danielle; Denis, Yann; Soulère, Laurent; Queneau, Yves; Talla, Emmanuel; Bonnefoy, Violaine; Guiliani, Nicolas

    2016-01-01

    While a functional quorum sensing system has been identified in the acidophilic chemolithoautotrophic Acidithiobacillus ferrooxidans ATCC 23270T and shown to modulate cell adhesion to solid substrates, nothing is known about the genes it regulates. To address the question of how quorum sensing controls biofilm formation in A. ferrooxidansT, the transcriptome of this organism in conditions in which quorum sensing response is stimulated by a synthetic superagonist AHL (N-acyl homoserine lactones) analog has been studied. First, the effect on biofilm formation of a synthetic AHL tetrazolic analog, tetrazole 9c, known for its agonistic QS activity, was assessed by fluorescence and electron microscopy. A fast adherence of A. ferrooxidansT cells on sulfur coupons was observed. Then, tetrazole 9c was used in DNA microarray experiments that allowed the identification of genes regulated by quorum sensing signaling, and more particularly, those involved in early biofilm formation. Interestingly, afeI gene, encoding the AHL synthase, but not the A. ferrooxidans quorum sensing transcriptional regulator AfeR encoding gene, was shown to be regulated by quorum sensing. Data indicated that quorum sensing network represents at least 4.5% (141 genes) of the ATCC 23270T genome of which 42.5% (60 genes) are related to biofilm formation. Finally, AfeR was shown to bind specifically to the regulatory region of the afeI gene at the level of the palindromic sequence predicted to be the AfeR binding site. Our results give new insights on the response of A. ferrooxidans to quorum sensing and on biofilm biogenesis. PMID:27683573

  5. Triacetic acid lactone production from Saccharomyces cerevisiae

    USDA-ARS?s Scientific Manuscript database

    Triacetic acid lactone (TAL) is a potential platform chemical produced from acetyl-CoA and malonyl-CoA by the Gerbera hybrida 2-pyrone synthase (2PS) gene. Studies are ongoing to optimize production, purification, and chemical modification of TAL, which can be used to create the commercial chemicals...

  6. New Sesquiterpene Lactones from Illicium floridanum

    PubMed

    Schmidt; Schmidt; Müller; Peters; Fronczek; Truesdale; Fischer

    1998-02-27

    In continuation of our phytochemical investigation of Illicium floridanum Ellis (American star anise, star bush), three new sesquiterpene lactones possessing the anisatin-type carbon skeleton (8,9-seco-prezizaane skeleton), 14-acetoxy-3-oxofloridanolide (1), 13-acetoxy-14-(n-butyryloxy)floridanolide (2), and 3beta-acetoxy-14-n-butyryloxy-10-deoxyfloridanolide (3), were isolated from fruits of this plant. Their structures were elucidated by 1D and 2D NMR measurements. The molecular structure of 1 was obtained by single crystal X-ray diffraction. The 11,3-delta-lactone structure of the compound previously described as debenzoyldunnianin in our previous communication, on grounds of NMR spectral evidence and X-ray crystallographic analysis is revised to a delta-lactone closed between C-11 and C-7 (compound 4). The neurotoxic sesquiterpene lactone anisatin (5) and its isomer 2alpha-hydroxyneoanisatin (3-deoxy-2alpha-hydroxyanisatin, 6) were also isolated and identified by spectroscopic means. The presence of the neurotoxin 5 in relatively high amounts in the fruits and leaves confirms and explains early reports on the toxicity of this plant.

  7. Chicory cultivars differ in sesquiterpene lactone composition

    USDA-ARS?s Scientific Manuscript database

    Chicory (Cichorium intybus L.) is a valuable forage species for small ruminants because it is nutritious and contains sesquiterpene lactones (SLs) that have anthelmintic activity. Three SLs, lactucin (lac), 8-deoxylactucin (dol), and lactucopicrin (lpic), occur in chicory leaves. Comprehensive dat...

  8. Formation of lactones from sialylated MUC1 glycopeptides.

    PubMed

    Pudelko, Maciej; Lindgren, Anna; Tengel, Tobias; Reis, Celso A; Elofsson, Mikael; Kihlberg, Jan

    2006-02-21

    The tumor-associated carbohydrate antigens TN, T, sialyl TN and sialyl T are expressed on mucins in several epithelial cancers. This has stimulated studies directed towards development of glycopeptide-based anticancer vaccines. Formation of intramolecular lactones involving sialic acid residues and suitably positioned hydroxyl groups in neighboring saccharide moieties is known to occur for glycolipids such as gangliosides. It has been suggested that these lactones are more immunogenic and tumor-specific than their native counterparts and that they might find use as cancer vaccines. We have now investigated if lactonization also occurs for the sialyl TN and T antigens of mucins. It was found that the model compound sialyl T benzyl glycoside , and the glycopeptide Ala-Pro-Asp-Thr-Arg-Pro-Ala from the tandem repeat of the mucin MUC1, in which Thr stands for the 2,3-sialyl-T antigen, lactonized during treatment with glacial acetic acid. Compound gave the 1''--> 2' lactone as the major product and the corresponding 1''--> 4' lactone as the minor product. For glycopeptide the 1''--> 4' lactone constitued the major product, whereas the 1''--> 2' lactone was the minor one. When lactonized was dissolved in water the 1''--> 4' lactone underwent slow hydrolysis, whereas the 1''--> 2' remained stable even after a 30 days incubation. In contrast the corresponding 2,6-sialyl-TN glycopeptide did not lactonize in glacial acetic acid.

  9. Acyl homoserine lactone changes the abundance of proteins and the levels of organic acids associated with stationary phase in Salmonella Enteritidis.

    PubMed

    de Almeida, Felipe Alves; Pimentel-Filho, Natan de Jesus; Carrijo, Lanna Clícia; Bento, Cláudia Braga Pereira; Baracat-Pereira, Maria Cristina; Pinto, Uelinton Manoel; de Oliveira, Leandro Licursi; Vanetti, Maria Cristina Dantas

    2017-01-01

    Quorum sensing (QS) is cell-cell communication mechanism mediated by signaling molecules known as autoinducers (AIs) that lead to differential gene expression. Salmonella is unable to synthesize the AI-1 acyl homoserine lactone (AHL), but is able to recognize AHLs produced by other microorganisms through SdiA protein. Our study aimed to evaluate the influence of AI-1 on the abundance of proteins and the levels of organic acids of Salmonella Enteritidis. The presence of N-dodecyl-homoserine lactone (C12-HSL) did not interfere on the growth or the total amount of extracted proteins of Salmonella. However, the abundance of the proteins PheT, HtpG, PtsI, Adi, TalB, PmgI (or GpmI), Eno, and PykF enhanced while the abundance of the proteins RplB, RplE, RpsB, Tsf, OmpA, OmpC, OmpD, and GapA decreased when Salmonella Enteritidis was anaerobically cultivated in the presence of C12-HSL. Additionally, the bacterium produced less succinic, lactic, and acetic acids in the presence of C12-HSL. However, the concentration of extracellular formic acid reached 20.46 mM after 24 h and was not detected when the growth was in the absence of AI-1. Considering the cultivation period for protein extraction, their abundance, process and function, as well as the levels of organic acids, we observed in cells cultivated in presence of C12-HSL a correlation with what is described in the literature as entry into the stationary phase of growth, mainly related to nitrogen and amino acid starvation and acid stress. Further studies are needed in order to determine the specific role of the differentially abundant proteins and extracellular organic acids secreted by Salmonella in the presence of quorum sensing signaling molecules. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. The advertisement calls of Quasipaa shini (Ahl, 1930) (Anura: Dicroglossidae).

    PubMed

    Kong, Shen Shen; Zheng, Rong Quan; Zhang, Qi Peng

    2016-12-04

    The genus Quasipaa (Family Dicroglossidae) is currently composed of 11 species distributed in China and Southeast Asia: Quasipaa acanthophora (Dubois & Ohler 2009), Q. boulengeri (Günther 1889), Q. courtoisi (Angel 1922), Q. delacouri (Angel 1928), Q. exilispinosa (Liu & Hu, 1975), Q. fasciculispina (Inger 1970), Q. jiulongensis (Huang & Liu, 1985), Q. shini (Ahl 1930), Q. spinosa (David 1875), Q. verrucospinosa (Bourret 1937), Q. yei (Chen, Qu & Jiang 2002) (Frost 2016). These species are morphologically similar, and their taxonomy is subject to controversy (Che et al. 2009). Analyses of nuclear and mitochondrial genes suggest the genus likely encompass additional cryptic species (Ye et al. 2013). Bioacoustics has contributed to studies on the taxonomy of the genus (Ye et al. 2013; Shen et al. 2015), however, to date, only the advertisement calls of Q. spinosa are known (Yu & Zheng 2009; Chen et al. 2012; Shen et al. 2015). Here, we describe the advertisement calls of Q. shini, which inhabits streams in the southern part of central China(Guizhou, Hunan, Guangxi and Jiangxi) and is characterized by the presence of keratinized skin spines on the lateral surfaces of the body.

  11. A locus on distal chromosome 10 (ahl4) affecting age-related hearing loss in A/J mice.

    PubMed

    Zheng, Qing Yin; Ding, Dalian; Yu, Heping; Salvi, Richard J; Johnson, Kenneth R

    2009-10-01

    The ahl locus, shown to be a strain-specific Cdh23 dimorphism, contributes to age-related hearing loss in many inbred mouse strains. A/J mice begin to lose hearing by 4 weeks of age, much earlier than C57BL/6J (B6) mice, although both strains have the same Cdh23(ahl) variant. Here, we use recombinant inbred strains, chromosome substitution strains, and a linkage backcross to map a locus on distal Chromosome 10, designated ahl4, that contributes to the early-onset hearing loss of A/J mice. Cochleae of 9-week-old A/J mice exhibit inner and outer hair cell loss from the basal turn through the apical turn, with outer hair cell loss at the base being severest. To quantify the progression of hair cell loss, cytocochleograms were evaluated from 0 to 20 weeks of age. A/J mice showed evidence of hair cell loss in the base of the cochlea as early as 14 days of age and the magnitude and extent of loss increased rapidly during the following 2-5 months. Hair cell loss occurred earlier and was much more severe and widespread in A/J mice than in B6 mice during the first 5 months of age. Spiral ganglion neurons, cells of the stria vascularis, and vestibular hair cell densities, however, appeared normal in 20-week-old A/J mice.

  12. The AT-hook Motif-containing Protein AHL22 Regulates Flowering Initiation by Modifying FLOWERING LOCUS T Chromatin in Arabidopsis*

    PubMed Central

    Yun, Ju; Kim, Youn-Sung; Jung, Jae-Hoon; Seo, Pil Joon; Park, Chung-Mo

    2012-01-01

    Coordination of the onset of flowering with developmental status and seasonal cues is critical for reproductive success in plants. Molecular genetic studies on Arabidopsis mutants that have alterations in flowering time have identified a wide array of genes that belong to distinct genetic flowering pathways. The flowering time genes are regulated through versatile molecular and biochemical mechanisms, such as controlled RNA metabolism and chromatin modifications. Recent studies have shown that a group of AT-hook DNA-binding motif-containing proteins plays a role in plant developmental processes and stress responses. Here, we demonstrate that the AT-hook protein AHL22 (AT-hook motif nuclear localized 22) regulates flowering time by modifying FLOWERING LOCUS T (FT) chromatin in Arabidopsis. AHL22 binds to a stretch of the AT-rich sequence in the FT locus. It interacts with a subset of histone deacetylases. An Arabidopsis mutant overexpressing the AHL22 gene (OE-AHL22) exhibited delayed flowering, and FT transcription was significantly reduced in the mutant. Consistent with the delayed flowering and FT suppression in the OE-AHL22 mutant, histone 3 (H3) acetylation was reduced and H3 lysine 9 dimethylation was elevated in the FT chromatin. We propose that AHL22 acts as a chromatin remodeling factor that modifies the architecture of FT chromatin by modulating both H3 acetylation and methylation. PMID:22442143

  13. Thermodynamic properties of sesquiterpene lactone grossheimin

    NASA Astrophysics Data System (ADS)

    Kasenova, Sh. B.; Atazhanova, G. A.; Sagintaeva, Zh. I.; Kasenov, B. K.; Kishkentaeva, A. S.; Adekenov, S. M.

    2016-08-01

    The enthalpy of dissolution of sesquiterpene lactone grossheimin C15H18O4 is measured using a DAK-I-IA calorimeter at a lactone/ethanol (96%) molar ratios equal to 1 : 18000, 1 : 36000, and 1 : 72000. The standard enthalpy of dissolution of grossheimin in a 96% ethanol solution is calculated based on the resulting data. The temperature dependence of the heat capacity of grossheimin C p ° ˜ f ( T) is studied by means of dynamic calorimetry using a IT-C-400 device in the temperature range of 298.15-423 K. An equation describing this dependence is derived. The standard enthalpies of combustion, melting, and formation of grossheimin are calculated using approximate methods.

  14. Guaiane sesquiterpene lactones from Salvia nubicola (Lamiaceae).

    PubMed

    Ali, Muhammad S; Ibrahim, Syed A; Ahmed, Shakeel; Lobkovsky, Emil

    2007-01-01

    A new sesquiterpene lactone, nubiol (1), belonging to the guaiane class, along with a dimer, bisnubidiol (2), has been isolated from Salvia nubicola collected from Quetta, Pakistan. The structures of both metabolites were elucidated with the aid of spectroscopic techniques including 2D-NMR. Additionally, the structure of nubiol (1) was finally confirmed via the single crystal X-ray diffraction. Nubiol (1) was found moderately active against Pseudomonas aeruginosa.

  15. Novel secoiridoid lactones from Jasminum multiflorum.

    PubMed

    Shen, Y C; Chen, C H

    1989-01-01

    Four new secoiridoid lactones, jasmolactones A [1], B [2], C [3], and D [4], were isolated from the aerial part of Jasminum multiflorum. The structures of these compounds, which contain a novel bicyclic 2-oxo-oxepano[4,5-c]pyran ring system, were established by spectral analyses and chemical correlations. Pharmacological testing revealed that jasmolactones B and D possess coronary vasodilating and cardiotropic activities.

  16. Quorum sensing activity of Serratia fonticola strain RB-25 isolated from an ex-landfill site.

    PubMed

    Ee, Robson; Lim, Yan-Lue; Tee, Kok-Keng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-03-12

    Quorum sensing is a unique bacterial communication system which permits bacteria to synchronize their behaviour in accordance with the population density. The operation of this communication network involves the use of diffusible autoinducer molecules, termed N-acylhomoserine lactones (AHLs). Serratia spp. are well known for their use of quorum sensing to regulate the expression of various genes. In this study, we aimed to characterized the AHL production of a bacterium designated as strain RB-25 isolated from a former domestic waste landfill site. It was identified as Serratia fonticola using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis and this was confirmed by 16S ribosomal DNA sequencing. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of S. fonticola strain RB-25 spent culture supernatant indicated the existence of three AHLs namely: N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl) homoserine-lactone (3-oxo-C6 HSL). This is the first report of the production of these AHLs in S. fonticola.

  17. Activity of isosteviol lactone on mitochondrial metabolism.

    PubMed

    Braguini, Welligton L; Gomes, Maria A Biazon; de Oliveira, Brás H; Carnieri, Eva G S; Rocha, Maria Eliane M; de Oliveira, Maria Benigna M

    2003-06-05

    Isosteviol lactone (LAC), a lactone derivative of the diterpenic acid isosteviol (ISO) was evaluated for its effect on the oxidative metabolism of mitochondria isolated from rat liver. In this model, LAC (1 mM) depressed the phosphorylation efficiency, as shown by the decreased respiratory control coefficient (RCC) and ADP/O ratio. LAC (1 mM) inhibited NADH oxidase (45%), succinate oxidase (34%) and promoted low-level inhibitions on succinate dehydrogenase (13%), succinate-cytochrome c oxide-reductase (23%), cytochrome c oxidase (10%), and NADH dehydrogenase (13%). Glutamate dehydrogenase was also a target for LAC, as it was 85% inhibited by 1 mM LAC. Cyclic voltammetry data showed that LAC, as well as ISO, does not undergo redox reactions under current experimental conditions. LAC (0.05-0.75 mM) inhibited the swelling dependent on the glutamate oxidation, 50% of the effect occurring at 0.5 mM LAC. Swelling supported by KNO(3) and valinomycin was also inhibited over all concentrations used of LAC and ISO, the effect being of a lower intensity for LAC, suggesting that the modification of the structure of ISO by lactonization diminished its interaction with the membrane. This could contribute to attenuation of the toxic effects described for ISO on mitochondrial function, such as those on respiratory chain enzymatic complexes and phosphorylating activity.

  18. Reduction of sugar lactones to hemiacetals with lithium triethylborohydride.

    PubMed

    Gonzalez, Cesar; Kavoosi, Sam; Sanchez, Andersson; Wnuk, Stanislaw F

    2016-09-02

    Reduction of ribono-1,4-lactones and gulono-1,4-lactone as well as ribono-1,5-lactone and glucono-1,5-lactones with LTBH (1.2 equiv.) in CH2Cl2 at 0 °C for 30 min provided the corresponding pentose or hexose hemiacetals in high yields. Commonly used in carbohydrate chemistry protecting groups such as trityl, benzyl, silyl, acetals and to some extent acyls are compatible with this reduction. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Attenuation of quorum sensing in the pathogen Acinetobacter baumannii using non-native N-acyl homoserine lactones

    PubMed Central

    Stacy, Danielle M.; Welsh, Michael A.; Rather, Philip N.; Blackwell, Helen E.

    2012-01-01

    Many bacterial pathogens use quorum sensing (QS) to control virulence. As a result, the development of methods to intercept QS has attracted significant interest as a potential anti-infective therapy. Acinetobacter baumannii has emerged as a pan-drug resistant pathogen and displays a remarkable ability to persist in hospital settings despite desiccation and antimicrobial treatment. Recent studies have shown that A. baumannii QS mutants have limited motility and fail to form mature biofilms – these phenotypes are linked to its ability to persist on biotic and abiotic surfaces and increase its pathogenicity. A. baumannii uses N-(3-hydroxydodecanoyl)-l-homoserine lactone (OH-dDHL) and its putative cognate receptor, AbaR, for QS. We sought to identify non-native ligands capable of blocking or promoting AbaR activity in A. baumannii for use as chemical probes to modulate QS phenotypes in this pathogen. We screened a focused library of synthetic, non-native N-acyl homoserine lactones (AHLs) to identify such compounds, and several highly potent antagonists and agonists were uncovered, with IC50 and EC50 values in the low micromolar range, respectively. The strongest AbaR antagonists largely contained aromatic acyl groups, whereas the AbaR agonists closely resembled OH-dDHL. Notably, the 10 most potent AbaR antagonists also strongly inhibited A. baumannii motility, and five antagonists reduced biofilm formation in A. baumannii by up to 40%. The discovery of these compounds is significant, as they represent, to our knowledge, the first non-native modulators of QS in A. baumannii to be reported and could find utility as new tools to study the role and timing of QS phenotypes in A. baumannii infections. PMID:22853441

  20. Lactones 46. Synthesis, antifeedant and antibacterial activity of γ-lactones with a p-methoxyphenyl substituent.

    PubMed

    Mazur, Marcelina; Skrobiszewski, Andrzej; Gładkowski, Witold; Podkowik, Magdalena; Bania, Jacek; Nawrot, Jan; Klejdysz, Tomasz; Wawrzeńczyk, Czesław

    2016-03-01

    Lactones are well known for their biological activity. Grosheimin and repin are potent deterrents against storage pests. The unsaturated lactones have exhibited a wide spectrum of antibacterial activity. In our study we focused on the synthesis and evaluation of the biological activity of anisaldehyde derivatives containing lactone function. Four new lactones were synthesized in one-step reductive dehalogenation or dehydrohalogenation reactions. These compounds, together with halolactones synthesized earlier, were tested for their antifeedant activity towards Sitophilus granaries, Trogoderma granarium and Tribolium confusum. The results of the tests showed that the highest activity, comparable with that of azadirachtin, towards all tested pests (total coefficient of deterrence 143.3-183.9) was observed for lactone with a vinyl substituent. The antibacterial activity of these compounds was also evaluated. The most potent lactone was active towards gram-positive bacteria strains. The results of biological tests showed that halogen atom removal significantly increased the antifeedant properties of γ-lactones with a p-methoxyphenyl substituent. Unsaturated lactones are most promising in the context of their possible industrial application as crop protection agents. Further structural modifications of lactones with aromatic rings are needed to find important structural factors increasing the antibacterial activity. © 2015 Society of Chemical Industry.

  1. Characterization of a novel enzyme-Starmerella bombicola lactone esterase (SBLE)-responsible for sophorolipid lactonization.

    PubMed

    Ciesielska, Katarzyna; Roelants, Sophie L K W; Van Bogaert, Inge N A; De Waele, Stijn; Vandenberghe, Isabel; Groeneboer, Sara; Soetaert, Wim; Devreese, Bart

    2016-11-01

    We recently discovered a novel enzyme in the exoproteome of Starmerella bombicola, which is structurally related to Candida antarctica lipase A. A knockout strain for this enzyme does no longer produce lactonic sophorolipids, prompting us to believe that this protein is the missing S. bombicola lactone esterase (SBLE). SBLE catalyzes a rather unusual reaction, i.e., an intramolecular esterification (lactonization) of acidic sophorolipids in an aqueous environment, which raised questions about its activity and mode of action. Here, we report the heterologous production of this enzyme in Pichia pastoris and its purification in a two-step strategy. Purified recombinant SBLE (rSBLE) was used to perform HPLC and liquid chromatography mass spectrometry (LCMS)-based assays with different sophorolipid mixtures. We experimentally confirmed that SBLE is able to perform ring closure of acetylated acidic sophorolipids. This substrate was selected for rSBLE kinetic studies to estimate the apparent values of K m . We established that rSBLE displays optimal activity in the pH range of 3.5 to 6 and has an optimal temperature in the range of 20 to 50 °C. Additionally, we generated a rSBLE mutant through site-directed mutagenesis of Ser194 in the predicted active site pocket and show that this mutant is lacking the ability to lactonize sophorolipids. We therefore propose that SBLE operates via the common serine hydrolase mechanism in which the catalytic serine residue is assisted by a His/Asp pair.

  2. Lactones 42. Stereoselective enzymatic/microbial synthesis of optically active isomers of whisky lactone.

    PubMed

    Boratyński, Filip; Smuga, Małgorzata; Wawrzeńczyk, Czesław

    2013-11-01

    Two different methods, enzyme-mediated reactions and biotrasformations with microorganisms, were applied to obtain optically pure cis- and trans-isomers of whisky lactone 4a and 4b. In the first method, eight alcohol dehydrogenases were investigated as biocatalysts to enantioselective oxidation of racemic erythro- and threo-3-methyloctane-1,4-diols (1a and 1b). Oxidation processes with three of them, alcohol dehydrogenases isolated from horse liver (HLADH) as well as recombinant from Escherichia coli and primary alcohol dehydrogenase (PADH I), were characterized by the highest degree of conversion with moderate enantioselectivity (ee=27-82%) of the reaction. In all enzymatic reactions enantiomerically enriched not naturally occurring isomers of trans-(-)-(4R,5S)-4b or cis-(+)-(4R,5R)-4a were formed preferentially. In the second strategy, based on microbial lactonization of γ-oxoacids, naturally occurring opposite isomers of whisky lactones were obtained. Trans-(+)-(4S,5R)-isomer (ee=99%) of whisky lactone 4b was stereoselectively formed as the only product of biotransformations of 3-methyl-4-oxooctanoic acid (5) catalyzed by Didimospheria igniaria KCH6651, Laetiporus sulphurens AM525, Chaetomium sp.1 KCH6670 and Saccharomyces cerevisiae AM464. Biotransformation of γ-oxoacid 5, in the culture of Beauveria bassiana AM278 and Pycnidiella resinae KCH50 afforded a mixtures of trans-(+)-(4S,5R)-4b with enantiomeric excess ee=99% and cis-(-)-(4S,5S)-4a with enantiomeric excesses ee=77% and ee=45% respectively.

  3. Degradation of bacterial quorum sensing signaling molecules by the microscopic yeast Trichosporon loubieri isolated from tropical wetland waters.

    PubMed

    Wong, Cheng-Siang; Koh, Chong-Lek; Sam, Choon-Kook; Chen, Jian Woon; Chong, Yee Meng; Yin, Wai-Fong; Chan, Kok-Gan

    2013-09-25

    Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast.

  4. Degradation of Bacterial Quorum Sensing Signaling Molecules by the Microscopic Yeast Trichosporon loubieri Isolated from Tropical Wetland Waters

    PubMed Central

    Wong, Cheng-Siang; Koh, Chong-Lek; Sam, Choon-Kook; Chen, Jian Woon; Chong, Yee Meng; Yin, Wai-Fong; Chan, Kok-Gan

    2013-01-01

    Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast. PMID:24072030

  5. Quorum sensing activity of Citrobacter amalonaticus L8A, a bacterium isolated from dental plaque.

    PubMed

    Goh, Share-Yuan; Khan, Saad Ahmed; Tee, Kok Keng; Abu Kasim, Noor Hayaty; Yin, Wai-Fong; Chan, Kok-Gan

    2016-02-10

    Cell-cell communication is also known as quorum sensing (QS) that happens in the bacterial cells with the aim to regulate their genes expression in response to increased cell density. In this study, a bacterium (L8A) isolated from dental plaque biofilm was identified as Citrobacter amalonaticus by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). Its N-acylhomoserine-lactone (AHL) production was screened by using two types of AHL biosensors namely Chromobacterium violaceum CV026 and Escherichia coli [pSB401]. Citrobacter amalonaticus strain L8A was identified and confirmed producing numerous types of AHL namely N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL) and N-hexadecanoyl-L-homoserine lactone (C16-HSL). We performed the whole genome sequence analysis of this oral isolate where its genome sequence reveals the presence of QS signal synthase gene and our work will pave the ways to study the function of the related QS genes in this bacterium.

  6. Quorum sensing activity of Citrobacter amalonaticus L8A, a bacterium isolated from dental plaque

    PubMed Central

    Goh, Share-Yuan; Khan, Saad Ahmed; Tee, Kok Keng; Abu Kasim, Noor Hayaty; Yin, Wai-Fong; Chan, Kok-Gan

    2016-01-01

    Cell-cell communication is also known as quorum sensing (QS) that happens in the bacterial cells with the aim to regulate their genes expression in response to increased cell density. In this study, a bacterium (L8A) isolated from dental plaque biofilm was identified as Citrobacter amalonaticus by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). Its N-acylhomoserine-lactone (AHL) production was screened by using two types of AHL biosensors namely Chromobacterium violaceum CV026 and Escherichia coli [pSB401]. Citrobacter amalonaticus strain L8A was identified and confirmed producing numerous types of AHL namely N-butyryl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-L-homoserine lactone (C8-HSL) and N-hexadecanoyl-L-homoserine lactone (C16-HSL). We performed the whole genome sequence analysis of this oral isolate where its genome sequence reveals the presence of QS signal synthase gene and our work will pave the ways to study the function of the related QS genes in this bacterium. PMID:26860259

  7. Discovery of new lactones in sweet cream butter oil.

    PubMed

    Sarrazin, Elise; Frerot, Eric; Bagnoud, Alain; Aeberhardt, Kasia; Rubin, Mark

    2011-06-22

    Sweet cream butter oil was analyzed to identify new volatile compounds that may contribute to its flavor, with an emphasis on lactones. The volatile part of butter oil was obtained by using short-path distillation. As some previously unknown lactones were detected in this first extract, it was fractionated further. The fatty acids were removed, and the extract was fractionated by flash chromatography. Three lactonic fractions possessing a creamy, buttery, and fatty character were investigated in depth by gas chromatography (GC) and mass spectrometry (MS) (EI and CI) and high-resolution GC-time-of-flight MS. Many lactones were identified by their mass fragmentation and by comparison with reference materials synthesized during this work. Six γ-lactones, five δ-lactones, and one ε-lactone were identified for the first time in butter oil, seven of them for the first time in a natural product. The possible contribution of these new lactones to the aroma of butter oil is briefly discussed.

  8. Lactones 12. Enzymatic lactonization of gamma, delta-epoxy esters by the apple fruit and Jerusalem artichoke bulb.

    PubMed

    Olejniczak, Teresa; Mironowicz, Agnieszka; Wawrzeńczyk, Czesław

    2003-06-01

    The enzymatic lactonization of three acyclic gamma, delta-epoxy esters (ethyl 3,7-dimethyl-4,5-epoxyoctanoate, ethyl 3,7,7-trimethyl-4,5-epoxyoctanoate, and ethyl 3,3,7-trimethyl-4,5-epoxyoctanoate) by apple fruit (Malus silvestris) and Jerusalem artichoke bulb (Helianthus tuberosus L.) was investigated. The substrates were transformed into a mixture of isomeric delta-hydroxy-gamma-lactones and gamma-hydroxy-delta-lactones. The gamma-lactones (yields ranging from 45-70%) predominated over delta-lactones (yields ranging from 8-40%). The composition of the product mixture depended on the structure of substrate as well as the biocatalyst. The enzymatic system in these biocatalysts also exhibited diastereoselectivity and enantioselectivity.

  9. Isovaleryl-homoserine lactone, an unusual branched-chain quorum-sensing signal from the soybean symbiont Bradyrhizobium japonicum

    PubMed Central

    Lindemann, Andrea; Pessi, Gabriella; Schaefer, Amy L.; Mattmann, Margrith E.; Christensen, Quin H.; Kessler, Aline; Hennecke, Hauke; Blackwell, Helen E.; Greenberg, E. Peter; Harwood, Caroline S.

    2011-01-01

    Many species of Proteobacteria communicate by using LuxI-LuxR–type quorum-sensing systems that produce and detect acyl-homoserine lactone (acyl-HSL) signals. Most of the known signals are straight-chain fatty acyl-HSLs, and evidence indicates that LuxI homologs prefer fatty acid-acyl carrier protein (ACP) over fatty acyl-CoA as the acyl substrate for signal synthesis. Two related LuxI homologs, RpaI and BtaI from Rhodopseudomonas palustris and photosynthetic stem-nodulating bradyrhizobia, direct production of the aryl-HSLs p-coumaroyl-HSL and cinnamoyl-HSL, respectively. Here we report that BjaI from the soybean symbiont Bradyrhizobium japonicum USDA110 is closely related to RpaI and BtaI and catalyzes the synthesis of isovaleryl-HSL (IV-HSL), a branched-chain fatty acyl-HSL. We show that IV-HSL induces expression of bjaI, and in this way IV-HSL functions like many other acyl-HSL quorum-sensing signals. Purified histidine-tagged BjaI was an IV-HSL synthase, which was active with isovaleryl-CoA but not detectably so with isovaleryl-ACP. This suggests that the RpaI-BtaI-BjaI subfamily of acyl-HSL synthases may use CoA- rather than ACP-linked substrates for acyl-HSL synthesis. The bjaI-linked bjaR1 gene is involved in the response to IV-HSL, and BjaR1 is sensitive to IV-HSL at concentrations as low as 10 pM. Low but sufficient levels of IV-HSL (about 5 nM) accumulate in B. japonicum culture fluid. The low levels of IV-HSL synthesis have likely contributed to the fact that the quorum-sensing signal from this bacterium has not been described elsewhere. PMID:21949379

  10. Quorum quenching in cultivable bacteria from dense marine coastal microbial communities.

    PubMed

    Romero, Manuel; Martin-Cuadrado, Ana-Belen; Roca-Rivada, Arturo; Cabello, Ana María; Otero, Ana

    2011-02-01

    Acylhomoserine lactone (AHLs)-mediated quorum-sensing (QS) processes seem to be common in the marine environment and among marine pathogenic bacteria, but no data are available on the prevalence of bacteria capable of interfering with QS in the sea, a process that has been generally termed 'quorum quenching' (QQ). One hundred and sixty-six strains isolated from different marine dense microbial communities were screened for their ability to interfere with AHL activity. Twenty-four strains (14.4%) were able to eliminate or significantly reduce N-hexanoyl-l-homoserine lactone activity as detected by the biosensor strain Chromobacterium violaceum CV026, a much higher percentage than that reported for soil isolates, which reinforces the ecological role of QS and QQ in the marine environment. Among these, 15 strains were also able to inhibit N-decanoyl-l-homoserine lactone activity and all of them were confirmed to enzymatically inactivate the AHL signals by HPLC-MS. Active isolates belonged to nine different genera of prevalently or exclusively marine origin, including members of the Alpha- and Gammaproteobacteria (8), Actinobacteria (2), Firmicutes (4) and Bacteroidetes (1). Whether the high frequency and diversity of cultivable bacteria with QQ activity found in near-shore marine isolates reflects their prevalence among pelagic marine bacterial communities deserves further investigation in order to understand the ecological importance of AHL-mediated QS and QQ processes in the marine environment.

  11. Quorum sensing activity of a Kluyvera sp. isolated from a Malaysian waterfall.

    PubMed

    Yunos, Nina Yusrina Muhamad; Tan, Wen-Si; Mohamad, Nur Izzati; Tan, Pui-Wan; Adrian, Tan-Guan-Sheng; Yin, Wai-Fong; Chan, Kok-Gan

    2014-05-08

    In many species of bacteria, the quorum sensing mechanism is used as a unique communication system which allows them to regulate gene expression and behavior in accordance with their population density. N-Acylhomoserine lactones (AHLs) are known as diffusible autoinducer molecules involved in this communication network. This finding aimed to characterize the production of AHL of a bacterial strain ND04 isolated from a Malaysian waterfall. Strain ND04 was identified as Kluyvera sp. as confirmed by molecular analysis of its 16S ribosomal RNA gene sequence. Kluyvera sp. is closely related to the Enterobacteriaceae family. Chromobacterium violaceum CV026 was used as a biosensor to detect the production of AHL by strain ND04. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis of strain ND04 showed our isolate produced two AHLs which are N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6 HSL) and N-3-oxo-octanoyl-L-homoserine lactone (3-oxo-C8 HSL).

  12. Lactones 41. Synthesis and microbial hydroxylation of unsaturated terpenoid lactones with p-menthane ring systems.

    PubMed

    Grudniewska, Aleksandra; Wawrzeńczyk, Czesław

    2013-03-01

    Racemic [(±)-4-isopropyl-1-methyl-7-oxa-cis-bicyclo[4.3.0]non-4-en-8-one] and optically active δ,ε-unsaturated lactones [(-)-(1R,6R)-4-isopropyl-1-methyl-7-oxabicyclo[4.3.0]non-4-en-8-one and (+)-(1S,6S)-4-isopropyl-1-methyl-7-oxabicyclo[4.3.0] non-4-en-8-one)] with the p-menthane system were obtained and their odoriferous properties were evaluated. Biotransformations of the racemic lactone with three fungal strains: Absidia cylindrospora AM336, Absidia glauca AM177 and Syncephalastrum racemosum AM105, were carried out. Microbial transformations afforded hydroxylactones with the hydroxy group in the allylic position.

  13. Lactones. 21. Synthesis and odoriferous properties of lactones with the p-menthane system.

    PubMed

    Dams, Iwona; Bialoniska, Agata; Ciunik, Zbigniew; Wawrzenczyk, Czesław

    2004-03-24

    Starting from (R)-(+)- and (S)-(-)-pulegone, enantiomeric pairs of esters and lactones with the p-menthane system were obtained. The Claisen rearrangement of allylic alcohols and iodolactonization of gamma,delta-unsaturated acids were the key steps of syntheses presented. The structures of compounds were determined by both spectroscopic and crystallographic methods. Some of the synthesized compounds are characterized by interesting odoriferous properties.

  14. The new group of non-pathogenic plant-associated nitrogen-fixing Burkholderia spp. shares a conserved quorum-sensing system, which is tightly regulated by the RsaL repressor.

    PubMed

    Suárez-Moreno, Zulma Rocí; Caballero-Mellado, Jesús; Venturi, Vittorio

    2008-07-01

    A novel group of nitrogen-fixing plant-associated Burkholderia species has emerged in the last few years. The purpose of this investigation was to determine if these species possess an N-acylhomoserine lactone (AHL) quorum-sensing (QS) cell-cell signalling system, and whether it is important for nitrogen fixation and other phenotypic features in Burkholderia kururiensis. It was determined that B. kururiensis, and other members of this Burkholderia species cluster, contain at least one highly conserved system, designated BraI/R, which produces and responds to N-dodecanoyl-3-oxo-homoserine lactone (C12-3-oxo-AHL). The BraI/R AHL QS is not involved in the regulation of nitrogen fixation or in several other important phenotypes, indicating that it may not be a global regulatory system. The BraI/R system is similar to LasI/R of Pseudomonas aeruginosa and, as with lasI/R, there is a repressor gene, rsaL, between the braI/R genes. B. kururiensis normally synthesizes very low levels of C12-3-oxo-AHL, but the situation dramatically changes when RsaL is missing since an rsaL mutant displays a marked increase in AHL production. This unique stringent regulation indicates that RsaL could be an on/off switch for AHL QS in B. kururiensis and the ability to produce very high levels of AHL also questions the role of this molecule in the novel group of Burkholderia. The presence of a well-conserved and distinct AHL QS system among all the diazotrophic Burkholderia is a further indication that they are closely related, and that this system might play an important and conserved role in the lifestyle of this novel group of bacterial species.

  15. Chemotypes in Achillea collina based on sesquiterpene lactone profile.

    PubMed

    Todorova, Milka; Trendafilova, Antoaneta; Mikhova, Bozhanka; Vitkova, Antonina; Duddeck, Helmut

    2007-07-01

    The lactone profile of six origins of Achillea collina growing in Bulgaria was studied and significant variability was observed. The reasons for the differences in the lactone composition are discussed. Twenty-five components in total were isolated and identified, while the presence of ten lactones was proved by intensive TLC analysis in comparison with reference compounds. The structures of the components 17, 20, 25-30 were established by spectroscopic methods. The structure of 7, a cyclization product of 6, was also discussed. The anti-inflammatory activity of some extracts, fractions and individual compounds was tested in vitro by determining the inhibitory effects on induced human neutrophils.

  16. New sources and antifungal activity of sesquiterpene lactones.

    PubMed

    Barrero, A F; Oltra, J E; Alvarez, M; Raslan, D S; Saúde, D A; Akssira, M

    2000-02-01

    In the search for new sources of sesquiterpene lactones, six Centaurea species have been analyzed. The activity against the fungus Cunninghamella echinulata of (+)-cnicin (1) and (+)-salonitenolide (2), isolated from the Centaurea plants, as well as that of (+)-costunolide (3), (-)-dehydrocostuslactone (4), (-)-lychnopholide (5) and (-)-eremantholide C (6), has been evaluated. Compounds 3 and 4 showed noticeable EC50 values, whilst more polar lactones were inactive. These results suggest that a relatively low polarity is one of the molecular requirements for the antifungal activity of sesquiterpene lactones.

  17. Characteristic gamma-lactone odor production of the genus Pityrosporum.

    PubMed Central

    Labows, J N; McGinley, K J; Leyden, J J; Webster, G F

    1979-01-01

    Mass spectrometric-gas chromatographic analysis of culture headspaces revealed that members of the genous Pityrosporum produce volatile gamma-lactones during growth on lipid-containing media. Representative members of other yeast genera found on humans failed to produce these compounds. Addition of lecithin, oleic acids, triolein, or human sebum to the culture media stimulated gamma-lactone production by Pityrosporum species. All yeasts tested produced isopentanol and phenylethanol. Production of gamma-lactones may serve as a valuable characteristic in the identification of organisms of the genus Pityrosporum. PMID:533274

  18. New sesquiterpene lactones from Ambrosia cumanensis Kunth.

    PubMed

    Jimenez-Usuga, Nora Del Socorro; Malafronte, Nicola; Cotugno, Roberta; De Leo, Marinella; Osorio, Edison; De Tommasi, Nunziatina

    2016-09-01

    Eleven sesquiterpene lactones, including three new natural products (1-3), were isolated from the n-butanolic extract of Ambrosia cumanensis Kunth. aerial parts. The structure of all isolated compounds was elucidated by 1D- and 2D-NMR, and MS analyses. All compounds were tested for their antiproliferative activity on HeLa, Jurkat, and U937 cell lines. Compound 3, 2,3-dehydropsilostachyn C, showed cytotoxic activity with different potency in all cell lines. By means of flow cytometric studies, compound 3 was demonstrated to induce in Jurkat cells a G2/M cell cycle block, while in U937 elicited both cytostatic and cytotoxic responses. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Novel anticancer alkene lactone from Persea americana.

    PubMed

    Falodun, Abiodun; Engel, Nadja; Kragl, Udo; Nebe, Barbara; Langer, Peter

    2013-06-01

    Persea americana Mill (Lauraceae) root bark is used in ethnomedicine for a variety of diseases including cancer. To isolate and characterize the chemical constituent in P. americana, and also to determine the anticancer property of a new alkene lactone from the root bark of P. americana. The MCF-7 cells were treated with different concentrations of the pure compound for 48 h. The percentage of cells in the various phases, online monitoring of metabolic changes and integrin receptor expression determined by flow cytometry. One novel alkene lactone (4-hydroxy-5-methylene-3-undecyclidenedihydrofuran-2 (3H)-one) (1) was isolated and characterized using 1D-NMR, 2D-NMR, infrared, UV and MS. At a concentration of 10 µg/mL, significant reduction of proliferation of MCF-7 was induced while MCF-12 A cell was significantly stimulated by 10 µg/mL. The IC50 value for MCF-7 cells is 20.48 µg/mL. Lower concentration of 1 harbor no significant effect on either MCF-7 or MCF-12A. The apoptotic rates of MCF-7 cells were increased significantly. At the final concentration 10 µg/mL, up to 80% of all breast cancer cells were dead. On the non-tumorigenic cell line MCF-12A, the same concentrations (1 and 10 µg/mL) of compound 1 caused significant enhanced apoptotic rates. A total of 1 µg/mL of 1 caused a decrease of α4-, α6-, β1- and β3-integrin expression. The compound caused a stimulatory effect on non-tumorigenic MCF-12A cells with respect to cell adhesion while tumorigenic MCF-7 cells detached continuously. This is the first report on the anticancer effects of this class of compound.

  20. In Vitro Characterization of a Recombinant AHL-Lactonase from Bacillus cereus Isolated from a Striped Catfish (Pangasianodon hypophthalmus) Pond.

    PubMed

    Tinh, Nguyen Thi Ngoc; Dung, Nguyen Viet; Trung, Cao Thanh; Thuy, Van Thi

    2013-12-01

    aiiA gene encoding AHL-lactonase was isolated from Bacillus cereus strain N26.2, originating from a striped catfish (Pangasianodon hypophthalmus) pond in Vietnam. This gene, abbreviated as aiiA(N26.2), was cloned and expressed in a competent Escherichia coli strain BL21(DE3)pLysS. The resulting protein, abbreviated as AiiAN26.2, was highly active in the pH range of 6-8 and could retain 80 % of the maximum activity under storage for 5 days at 4 °C or for 3 days at 20 °C. These properties of AiiAN26.2 protein confers its future application via feed supplementation, with the purpose of controlling aquaculture pathogens which regulate the virulence via a quorum sensing system.

  1. Effect of α-tocopherol on lactone formation in marbled beef and changes in lactone volatility during storage.

    PubMed

    Watanabe, Akira; Imanari, Mai; Yonai, Miharu; Shiba, Nobuya

    2012-06-01

    Dynamic-headspace sampling with a standard-addition method was employed to quantitatively analyze aliphatic lactones in rendered fat from marbled beef and to evaluate the effect of the matrix on volatility. Further, the effects of different levels of the antioxidant α-tocopherol on lactone formation were examined. The slopes of the linear regression curves from the standard-addition method were significantly changed (P < 0.05 or 0.01) for all lactones after storage, with the exception of γ-octalactone, indicating the volatility of the longer-chain lactones were increased after storage. The concentrations of γ-lactones were increased after 7 d of storage at 2 °C (P < 0.01), and the α-tocopherol content in the meat affected the formation of γ-octalactone (P < 0.05) and γ-nonalactone (P < 0.01). The greatest increase was observed for γ-nonalactone in the lowest α-tocopherol (2.9 ppm) group: the concentration of 51.4 ppb was 11.7-fold higher than that before storage. Meanwhile, δ-tetradecalactone in the highest α-tocopherol (28.8 ppm) group showed the highest concentration for the lactones at 415.8 ppb, which was 2.6-fold higher than the concentration before storage. The effect of α-tocopherol was unclear for the δ-lactones. The results indicate that most of the γ-lactones are produced by oxidation during storage but that the other lactones are also generated by other processes as well.

  2. Mechanisms of lactone hydrolysis in neutral and alkaline conditions.

    PubMed

    Gómez-Bombarelli, Rafael; Calle, Emilio; Casado, Julio

    2013-07-19

    The neutral and base-catalyzed hydrolysis of nine carboxylic acid esters was studied using a hybrid supermolecule-PCM approach including six explicit water molecules. The molecules studied included two linear esters, four β-lactones, two γ-lactones, and one δ-lactone: ethyl acetate and methyl formate, β-propiolactone, β-butyrolactone, β-isovalerolactone, diketene (4-methyleneoxetan-2-one), γ-butyrolactone, 2(5H)-furanone, and δ-valerolactone. DFT and ab initio methods were used to analyze the features of the various possible hydrolysis mechanisms. For all compounds, reasonable to very good qualitative and quantitative agreement with experimental work was found, and evidence is provided to support long-standing hypotheses regarding the role of solvent molecule as a base catalyst. In addition, novel evidence is presented for the existence of an elimination-addition mechanism in the basic hydrolysis of diketene. A parallel work addresses the acid-catalyzed hydrolysis of lactones.

  3. Rh-Catalyzed Conjugate Addition of Aryl and Alkenyl Boronic Acids to α-Methylene-β-lactones: Stereoselective Synthesis of trans-3,4-Disubstituted β-Lactones.

    PubMed

    Malapit, Christian A; Luvaga, Irungu K; Caldwell, Donald R; Schipper, Nicholas K; Howell, Amy R

    2017-09-01

    A one-step preparation of 3,4-disubstituted β-lactones through Rh-catalyzed conjugate addition of aryl or alkenyl boronic acids to α-methylene-β-lactones is described. The operationally simple, stereoselective transformation provides a broad range of β-lactones from individual α-methylene-β-lactone templates. This methodology allowed for a direct, final-step C-3 diversification of nocardiolactone, an antimicrobial natural product.

  4. Sesquiterpene lactones from Achillea collina J. Becker ex Reichenb.

    PubMed

    Trendafilova, Antoaneta; Todorova, Milka; Mikhova, Bozhanka; Vitkova, Antonina; Duddeck, Helmut

    2006-04-01

    The flower heads of Achillea collina afforded 31 individual sesquiterpene lactones, among which nine guaianolides (1, 16, 20, 21, 23, 27-30), a germacranolide (18) and a dimeric guaianolide (31) were found to be new natural products. The lactones 2-4, 12, 14, 15, 17, 19 and 25 were isolated for the first time from the investigated species. Their structures were established by spectral methods.

  5. Diterpene lactones with labdane, halimane and clerodane frameworks.

    PubMed

    Silva, Lúcia; Gomes, Arlindo C; Rodilla, Jesus M L

    2011-04-01

    The labdane, halimane and clerodane type diterpenoids are compounds that have been isolated in plants of several families. These molecules and their derivatives with a lactone group on the side chain or on the decaline system, have a great interest because of their biological properties as insect antifeedant, antiviral, cytotoxic and trypanocidal. The scope of this review is lactones diterpenoids with labdane, halimane and clerodane frameworks.

  6. Kava lactones and the kava-kava controversy.

    PubMed

    Whitton, Peter A; Lau, Andrew; Salisbury, Alicia; Whitehouse, Julie; Evans, Christine S

    2003-10-01

    Kava-kava is a traditional beverage of the South Pacific islanders and has had centuries of use without major side effects. Standardised extracts of kava-kava produced in Europe have led to many serious health problems and even to death. The extraction process (aqueous vs. acetone in the two types of preparations) is responsible for the difference in toxicity as extraction of glutathione in addition to the kava lactones is important to provide protection against hepatotoxicity. The Michael reaction between glutathione and kava lactones, resulting in opening of the lactone ring, reduces the side effects of the kava kava extracts. This protective activity was demonstrated using Acanthamoebae castellanii in which 100% cell death occurred with 100 mg ml(-1) kava lactones alone, and 40% cell death with a mixture of 100 mg ml (-1)glutathione and 100 mg ml (-1) kava lactones. A comparison of kava lactone toxicity with other pharmaceutical products is discussed and recommendations made for safe usage of kava-kava products

  7. Treatment of MDR1 Mutant Dogs with Macrocyclic Lactones

    PubMed Central

    Geyer, Joachim; Janko, Christina

    2012-01-01

    P-glycoprotein, encoded by the multidrug resistance gene MDR1, is an ATP-driven drug efflux pump which is highly expressed at the blood-brain barrier of vertebrates. Drug efflux of macrocyclic lactones by P-glycoprotein is highly relevant for the therapeutic safety of macrocyclic lactones, as thereby GABA-gated chloride channels, which are confined to the central nervous system in vertebrates, are protected from high drug concentrations that otherwise would induce neurological toxicity. A 4-bp deletion mutation exists in the MDR1 gene of many dog breeds such as the Collie and the Australian Shepherd, which results in the expression of a non-functional P-glycoprotein and is associated with multiple drug sensitivity. Accordingly, dogs with homozygous MDR1 mutation are in general prone to neurotoxicity by macrocyclic lactones due to their increased brain penetration. Nevertheless, treatment of these dogs with macrocyclic lactones does not inevitably result in neurological symptoms, since, the safety of treatment highly depends on the treatment indication, dosage, route of application, and the individual compound used as outlined in this review. Whereas all available macrocyclic lactones can safely be administered to MDR1 mutant dogs at doses usually used for heartworm prevention, these dogs will experience neurological toxicity following a high dose regimen which is common for mange treatment in dogs. Here, we review and discuss the neurotoxicological potential of different macrocyclic lactones as well as their treatment options in MDR1 mutant dogs. PMID:22039792

  8. Prevalence of LuxR- and LuxI-type quorum sensing circuits in members of the Populus deltoides microbiome

    SciTech Connect

    Schaefer, Amy L; Lappala, Colin; Morlen, Ryan; Pelletier, Dale A; Lu, Tse-Yuan; Lankford, Patricia K; Harwood, Caroline S; Greenberg, E. Peter

    2013-01-01

    We are interested in the root microbiome of the fast-growing Eastern cottonwood tree, Populus 25 deltoides. There is a large bank of bacterial isolates from P. deltoides and there are 44 draft 26 genomes of bacterial endophyte and rhizosphere isolates. As a first step in efforts to understand 27 the roles of bacterial communication and plant-bacterial signaling in P. deltoides we focused on 28 the prevalence of acyl-homoserine lactone (AHL) quorum sensing signal production and 29 reception in members of the P. deltoides microbiome. We screened 129 bacterial isolates for 30 AHL production using a broad-spectrum bioassay that responds to many but not all AHLs, and 31 we queried the available genome sequences of microbiome isolates for homologs of AHL 32 synthase and receptor genes. AHL signal production was detected in 40% of 129 strains tested. 33 Positive isolates included -, - and -Proteobacteria. Members of the luxI family of AHL 34 synthases were identified in 18 of 39 Proteobacteria genomes including genomes of some 35 isolates that tested negative in the bioassay. Members of the luxR family of transcription factors, 36 that include AHL-responsive factors, were more abundant than luxI homologs. There were 72 in 37 the 39 Proteobacteria genomes. Some of the luxR homologs appear to be members of a 38 subfamily of LuxRs that respond to as yet unknown plant signals rather than bacterial AHLs. 39 Apparently, there is a substantial capacity for AHL cell-to-cell communication in Proteobacteria 40 of the P. deltoides microbiota and there are also Proteobacteria with LuxR homologs of the type 41 hypothesized to respond to plant signals or cues.

  9. LuxR- and LuxI-Type Quorum-Sensing Circuits Are Prevalent in Members of the Populus deltoides Microbiome

    PubMed Central

    Schaefer, Amy L.; Lappala, Colin R.; Morlen, Ryan P.; Pelletier, Dale A.; Lu, Tse-Yuan S.; Lankford, Patricia K.; Harwood, Caroline S.

    2013-01-01

    We are interested in the root microbiome of the fast-growing Eastern cottonwood tree, Populus deltoides. There is a large bank of bacterial isolates from P. deltoides, and there are 44 draft genomes of bacterial endophyte and rhizosphere isolates. As a first step in efforts to understand the roles of bacterial communication and plant-bacterial signaling in P. deltoides, we focused on the prevalence of acyl-homoserine lactone (AHL) quorum-sensing-signal production and reception in members of the P. deltoides microbiome. We screened 129 bacterial isolates for AHL production using a broad-spectrum bioassay that responds to many but not all AHLs, and we queried the available genome sequences of microbiome isolates for homologs of AHL synthase and receptor genes. AHL signal production was detected in 40% of 129 strains tested. Positive isolates included members of the Alpha-, Beta-, and Gammaproteobacteria. Members of the luxI family of AHL synthases were identified in 18 of 39 proteobacterial genomes, including genomes of some isolates that tested negative in the bioassay. Members of the luxR family of transcription factors, which includes AHL-responsive factors, were more abundant than luxI homologs. There were 72 in the 39 proteobacterial genomes. Some of the luxR homologs appear to be members of a subfamily of LuxRs that respond to as-yet-unknown plant signals rather than bacterial AHLs. Apparently, there is a substantial capacity for AHL cell-to-cell communication in proteobacteria of the P. deltoides microbiota, and there are also Proteobacteria with LuxR homologs of the type hypothesized to respond to plant signals or cues. PMID:23851092

  10. High yield expression of an AHL-lactonase from Bacillus sp. B546 in Pichia pastoris and its application to reduce Aeromonas hydrophila mortality in aquaculture

    PubMed Central

    2010-01-01

    Background Aeromonas hydrophila is a serious pathogen and can cause hemorrhagic septicemia in fish. To control this disease, antibiotics and chemicals are widely used which can consequently result in "superbugs" and chemical accumulation in the food chain. Though vaccine against A. hydrophila is available, its use is limited due to multiple serotypes of this pathogen and problems of safety and efficacy. Another problem with vaccination is the ability to apply it to small fish especially in high numbers. In this study, we tried a new way to attenuate the A. hydrophila infection by using a quorum quenching strategy with a recombinant AHL-lactonase expressed in Pichia pastoris. Results The AHL-lactonase (AiiAB546) from Bacillus sp. B546 was produced extracellularly in P. pastoris with a yield of 3,558.4 ± 81.3 U/mL in a 3.7-L fermenter when using 3-oxo-C8-HSL as the substrate. After purification with a HiTrap Q Sepharose column, the recombinant homogenous protein showed a band of 33.6 kDa on SDS-PAGE, higher than the calculated molecular mass (28.14 kDa). Deglycosylation of AiiAB546 with Endo H confirmed the occurrence of N-glycosylation. The purified recombinant AiiAB546 showed optimal activity at pH 8.0 and 20°C, exhibited excellent stability at pH 8.0-12.0 and thermal stability at 70°C, was firstly confirmed to be significantly protease-resistant, and had wide substrate specificity. In application test, when co-injected with A. hydrophila in common carp, recombinant AiiAB546 decreased the mortality rate and delayed the mortality time of fish. Conclusions Our results not only indicate the possibility of mass-production of AHL-lactonase at low cost, but also open up a promising foreground of application of AHL-lactonase in fish to control A. hydrophila disease by regulating its virulence. To our knowledge, this is the first report on heterologous expression of AHL-lactonase in P. pastoris and attenuating A. hydrophila virulence by co-injection with AHL

  11. Effects of dietary Lactobacillus plantarum and AHL lactonase on the control of Aeromonas hydrophila infection in tilapia.

    PubMed

    Liu, Wenshu; Ran, Chao; Liu, Zhi; Gao, Qian; Xu, Shude; Ringø, Einar; Myklebust, Reidar; Gu, Zemao; Zhou, Zhigang

    2016-08-01

    This study addressed the effects of dietary Lactobacillus plantarum or/and N-acylated homoserine lactonase (AHL lactonase) on controlling Aeromonas  hydrophila infection in juvenile hybrid tilapia (Oreochromis niloticus♀ × O. aureus ♂). Fish were fed Lb. plantarum subsp. plantarum strain JCM1149 (10(8)  CFU/g feed) or/and AHL lactonase AIO6 (4 U/g) and were exposed to a chronic challenge of A. hydrophila NJ-1 (10(5)  cells/mL) for 14 days. Intestinal (foregut) alkaline phosphatase (IAP) activities were evaluated 1 day post challenge to reflect the resistance of fish against A. hydrophila infection. Parallel groups of fish with the same dietary assignments while unchallenged were also included to investigate the effect of dietary Lb. plantarum or/and AIO6 supplementation on gut health of tilapia. The results showed that IAP activity was significantly lower in fish fed with diets supplemented with Lb. plantarum JCM1149 or the combination of Lb. plantarum JCM1149 and AIO6, indicating enhanced resistance against A. hydrophila. Light microscopy and transmission electron microscopy images of foregut revealed damage caused by A. hydrophila NJ-1, but dietary Lb. plantarumJCM1149 or/and AIO6 significantly alleviated the damages. Compared to the fish immersed in A. hydrophila NJ-1, dietary Lb. plantarum JCM1149 or AIO6 could maintain the microvilli length in the foregut of tilapia. However, among the unchallenged groups of fish, the microvilli length in the foregut of tilapia fed AIO6 (singly or combination) and the microvilli density of tilapia fed AIO6 (singly) were significantly lower than those of the control, though the microvilli density in the combination treatment was significantly improved. Additionally, the dietary Lb. plantarum JCM1149 could down-regulate the expression of stress-related gene in the gut after the acute phase. In conclusion, the dietary Lb. plantarum JCM1149 is recommended to control the A. hydrophila infection in

  12. Application of molecular docking and ONIOM methods for the description of interactions between anti-quorum sensing active (AHL) analogues and the Pseudomonas aeruginosa LasR binding site.

    PubMed

    Ahumedo, Maicol; Drosos, Juan Carlos; Vivas-Reyes, Ricardo

    2014-05-01

    Molecular docking methods were applied to simulate the coupling of a set of nineteen acyl homoserine lactone analogs into the binding site of the transcriptional receptor LasR. The best pose of each ligand was explored and a qualitative analysis of the possible interactions present in the complex was performed. From the results of the protein-ligand complex analysis, it was found that residues Tyr-64 and Tyr-47 are involved in important interactions, which mainly determine the antagonistic activity of the AHL analogues considered for this study. The effect of different substituents on the aromatic ring, the common structure to all ligands, was also evaluated focusing on how the interaction with the two previously mentioned tyrosine residues was affected. Electrostatic potential map calculations based on the electron density and the van der Waals radii were performed on all ligands to graphically aid in the explanation of the variation of charge density on their structures when the substituent on the aromatic ring is changed through the elements of the halogen group series. A quantitative approach was also considered and for that purpose the ONIOM method was performed to estimate the energy change in the different ligand-receptor complex regions. Those energy values were tested for their relationship with the corresponding IC50 in order to establish if there is any correlation between energy changes in the selected regions and the biological activity. The results obtained using the two approaches may contribute to the field of quorum sensing active molecules; the docking analysis revealed the role of some binding site residues involved in the formation of a halogen bridge with ligands. These interactions have been demonstrated to be responsible for the interruption of the signal propagation needed for the quorum sensing circuit. Using the other approach, the structure-activity relationship (SAR) analysis, it was possible to establish which structural characteristics

  13. Stabilization of the Karenitecin® lactone by alpha-1 acid glycoprotein.

    PubMed

    Yao, Shijie; Petluru, Pavankumar; Parker, Aulma; Ding, Daoyuan; Chen, Xinghai; Huang, Qiuli; Kochat, Harry; Hausheer, Frederick

    2015-04-01

    Camptothecins contain a lactone ring that is necessary for antitumor activity, and hydrolysis of the lactone ring yields an inactive carboxylate species. Human serum albumin (HSA) and alpha-1 acid glycoprotein (AGP) are clinically significant plasma proteins thought to have important roles in camptothecin lactone stability. Herein, we examined the effect(s) of HSA and AGP on the lactone stability of Karenitecin, a novel, highly lipophilic camptothecin analog, currently at the phase 3 clinical testing stage. An AGP-immobilized protein column was used to develop HPLC methods to evaluate the effect(s) of physiologically relevant HSA and AGP concentrations on the lactone/carboxylate ratio and hydrolysis kinetics of Karenitecin, camptothecin (CPT), and topotecan (TPT). Physiologically relevant concentrations of HSA and AGP substantially slowed Karenitecin lactone hydrolysis. AGP was notably more effective at protecting the Karenitecin lactone from hydrolysis than HSA was in promoting hydrolysis. Additionally, AGP reversed the hydrolysis of partially hydrolyzed Karenitecin lactone. In contrast, HSA and AGP had minimal effects on hydrolysis of the TPT lactone, while the AGP/HSA solutions dramatically accelerated hydrolysis of the CPT lactone. AGP strongly enhances the lactone stability of Karenitecin. Since Karenitecin is highly protein-bound in human plasma and exhibits greater lactone stability, relative to other camptothecins, in patient plasma samples, this newly identified role of AGP in promoting lactone stability may have important implications for the design of more effective anticancer agents within the Karentecin™ and camptothecin classes.

  14. Switch of SpnR function from activating to inhibiting quorum sensing by its exogenous addition

    SciTech Connect

    Takayama, Yuriko; Kato, Norihiro

    2016-09-02

    The opportunistic human pathogen Serratia marcescens AS-1 produces the N-hexanoylhomoserine lactone (C6HSL) receptor SpnR, a homologue of LuxR from Vibrio fischeri, which activates pig clusters to produce the antibacterial prodigiosin. In this study, we attempted to artificially regulate quorum sensing (QS) by changing the role of SpnR in N-acylhomoserine lactone (AHL)-mediated QS. SpnR was obtained as a fusion protein tagged with maltose-binding protein (MBP) from overexpression in Escherichia coli, and its specific affinity to C6HSL was demonstrated by quartz crystal microbalance analysis and AHL-bioassay with Chromobacterium violaceum CV026. Prodigiosin production was effectively inhibited by externally added MBP-SpnR in both wild-type AS-1 and the AHL synthase-defective mutant AS-1(ΔspnI). For the mutant, the induced amount of prodigiosin was drastically reduced to approximately 4% with the addition of 18 μM MBP-SpnR to the liquid medium, indicating 81% trapping of C6HSL. A system for inhibiting QS can be constructed by adding exogenous AHL receptor to the culture broth to keep the concentration of free AHL low, whereas intracellular SpnR naturally functions as the activator in response to QS. - Highlights: • Quorum sensing (QS) regulates the expression of some bacterial genes. • We added an AHL receptor to culture media to inhibit QS in Serratia marcescens AS-1. • The exogenous receptor effectively bound C6HSL and inhibited QS. • This approach can be used to artificially regulate AHL-mediated QS.

  15. Biosynthesis of Sesquiterpene Lactones in Pyrethrum (Tanacetum cinerariifolium)

    PubMed Central

    Ramirez, Aldana M.; Saillard, Nils; Yang, Ting; Franssen, Maurice C. R.; Bouwmeester, Harro J.; Jongsma, Maarten A.

    2013-01-01

    The daisy-like flowers of pyrethrum (Tanacetum cinerariifolium) are used to extract pyrethrins, a botanical insecticide with a long history of safe and effective use. Pyrethrum flowers also contain other potential defense compounds, particularly sesquiterpene lactones (STLs), which represent problematic allergenic residues in the extracts that are removed by the pyrethrum industry. The STLs are stored in glandular trichomes present on the pyrethrum achenes, and have been shown to be active against herbivores, micro-organisms and in the below-ground competition with other plants. Despite these reported bioactivities and industrial significance, the biosynthetic origin of pyrethrum sesquiterpene lactones remains unknown. In the present study, we show that germacratrien-12-oic acid is most likely the central precursor for all sesquiterpene lactones present in pyrethrum. The formation of the lactone ring depends on the regio- (C6 or C8) and stereo-selective (α or β) hydroxylation of germacratrien-12-oic acid. Candidate genes implicated in three committed steps leading from farnesyl diphosphate to STL and other oxygenated derivatives of germacratrien-12-oic acid were retrieved from a pyrethrum trichome EST library, cloned, and characterized in yeast and in planta. The diversity and distribution of sesquiterpene lactones in different tissues and the correlation with the expression of these genes are shown and discussed. PMID:23741445

  16. Quorum sensing of bacteria and trans-kingdom interactions of N-acyl homoserine lactones with eukaryotes.

    PubMed

    Hartmann, Anton; Schikora, Adam

    2012-06-01

    Many environmental and interactive important traits of bacteria, such as antibiotic, siderophore or exoenzyme (like cellulose, pectinase) production, virulence factors of pathogens, as well as symbiotic interactions, are regulated in a population density-dependent manner by using small signaling molecules. This phenomenon, called quorum sensing (QS), is widespread among bacteria. Many different bacterial species are communicating or "speaking" through diffusible small molecules. The production often is sophisticatedly regulated via an autoinducing mechanism. A good example is the production of N-acyl homoserine lactones (AHL), which occur in many variations of molecular structure in a wide variety of Gram-negative bacteria. In Gram-positive bacteria, other compounds, such as peptides, regulate cellular activity and behavior by sensing the cell density. The degradation of the signaling molecule--called quorum quenching--is probably another important integral part in the complex quorum sensing circuit. Most interestingly, bacterial quorum sensing molecules also are recognized by eukaryotes that are colonized by QS-active bacteria. In this case, the cross-kingdom interaction can lead to specific adjustment and physiological adaptations in the colonized eukaryote. The responses are manifold, such as modifications of the defense system, modulation of the immune response, or changes in the hormonal status and growth responses. Thus, the interaction with the quorum sensing signaling molecules of bacteria can profoundly change the physiology of higher organisms too. Higher organisms are obligatorily associated with microbial communities, and these truly multi-organismic consortia, which are also called holobionts, can actually be steered via multiple interlinked signaling substances that originate not only from the host but also from the associated bacteria.

  17. Seasonal variation in sesquiterpene lactone concentration and composition of forage chicory (Cichorium intybus L.) cultivars

    USDA-ARS?s Scientific Manuscript database

    Chicory (Cichorium intybus L.) herbage contains sesquiterpene lactones that are believed to help control gastrointestinal nematodes in small ruminants. Because the anthelmintic effect could be related to both total sesquiterpene lactone concentration and the proportions of the principal constituent...

  18. C-Ring Cannabinoid Lactones: A Novel Cannabinergic Chemotype

    PubMed Central

    2014-01-01

    As a part of our controlled-deactivation ligand development project, we recently disclosed a series of (−)-Δ8-tetrahydrocannabinols (THCs) with a metabolically labile ester group at the 2′-position of the side chain. Now, we have replaced the C-ring in the classical THC structure with a hydrolyzable seven-membered lactone. One of the synthesized analogues binds with high affinity to the CB1 receptor (Ki = 4.6 nM) and exhibits much lower affinities for the mCB2 and the hCB2. Also, in vitro functional characterization found the compound to be an agonist at rCB1. Consistent with our rational design, the lead cannabinergic lactone identified here is susceptible to metabolic inactivation by plasma esterases, while the respective acid metabolite is inactive at CB receptors. These results are highlighted with molecular modeling of the two regiosomeric lactones. PMID:24900848

  19. Relationship between Menthiafolic Acid and Wine Lactone in Wine.

    PubMed

    Giaccio, Joanne; Curtin, Chris D; Sefton, Mark A; Taylor, Dennis K

    2015-09-23

    Menthiafolic acid (6-hydroxy-2,6-dimethylocta-2,7-dienoic acid, 2a) was quantified by GC-MS in 28 white wines, 4 Shiraz wines, and for the first time in 6 white grape juice samples. Menthiafolic acid was detected in all but one of the wine samples at concentrations ranging from 26 to 342 μg/L and in the juice samples from 16 to 236 μg/L. Various model fermentation experiments showed that some menthiafolic acid in wine could be generated from the grape-derived menthiafolic acid glucose ester (2b) during alcoholic and malolactic fermentation. Samples containing high concentrations of menthiafolic acid were also analyzed by enantioselective GC-MS and were shown to contain this compound in predominantly the (S)-configuration. Enantioselective analysis of wine lactone (1) in one of these samples, a four-year-old Chardonnay wine showed, for the first time, the presence of the 3R,3aR,7aS isomer of wine lactone (1b), which is the enantiomer of the form previously reported as the sole isomer present in young wine samples. The weakly odorous 3R,3aR,7aS 1b form comprised 69% of the total wine lactone in the sample. On the basis of the enantioselectivity of the hydrolytic conversion of menthiafolic acid to wine lactone at pH 3.0 determined previously and the relative proportions of (R)- and (S)-menthiafolic acid in the Chardonnay wine, the predicted ratio of wine lactone enantiomers that would be formed from hydrolysis at ambient temperature of the menthiafolic acid present in this wine was close to the ratio measured, which was consistent with menthiafolic acid being the major or sole precursor to wine lactone in this sample.

  20. Synthesis of γ- and δ-lactone natural products by employing a trans-cis isomerization/lactonization strategy.

    PubMed

    Ono, Machiko; Kato, Keisuke; Akita, Hiroyuki

    2013-01-01

    Alkaline hydrolysis of 4-hydroxy- or/and 5-hydroxy-(2E)-alkenoate followed by acid treatment gave the corresponding (2E)-alkenoic acids which were subjected to lactone formation reaction without further purification. The crude acids were treated with 2,4,6-trichlorobenzoyl chloride in pyridine to afford γ-lactone or δ-lactone, respectively, accompanied by trans-cis isomerization. By this procedure, (±)-(4,5)-trans-5-benzyloxy-2-hexen-4-olide (90% overall yield), (S)-5-hydroxy-2-penten-4-olide (86% overall yield), (4S,5R)-5-hydroxy-2-hexen-4-olide (86% overall yield), (4R,5S)-5-hydroxy-2-hexen-4-olide (82% overall yield), (S)-parasorbic acid (58% overall yield) and natural product, (5R,7S)-7-hydroxy-2-octen-5-olide (euscapholide: 20% overall yield) were synthesized.

  1. N,N'-alkylated Imidazolium-derivatives act as quorum-sensing inhibitors targeting the Pectobacterium atrosepticum-induced symptoms on potato tubers.

    PubMed

    des Essarts, Yannick Raoul; Sabbah, Mohamad; Comte, Arnaud; Soulère, Laurent; Queneau, Yves; Dessaux, Yves; Hélias, Valérie; Faure, Denis

    2013-10-08

    Bacteria belonging to the Pectobacterium genus are the causative agents of the blackleg and soft-rot diseases that affect potato plants and tubers worldwide. In Pectobacterium, the expression of the virulence genes is controlled by quorum-sensing (QS) and N-acylhomoserine lactones (AHLs). In this work, we screened a chemical library of QS-inhibitors (QSIs) and AHL-analogs to find novel QSIs targeting the virulence of Pectobacterium. Four N,N'-bisalkylated imidazolium salts were identified as QSIs; they were active at the µM range. In potato tuber assays, two of them were able to decrease the severity of the symptoms provoked by P. atrosepticum. This work extends the range of the QSIs acting on the Pectobacterium-induced soft-rot disease.

  2. Efficient Biostimulation of Native and Introduced Quorum-Quenching Rhodococcus erythropolis Populations Is Revealed by a Combination of Analytical Chemistry, Microbiology, and Pyrosequencing

    PubMed Central

    Cirou, Amélie; Mondy, Samuel; An, Shu; Charrier, Amélie; Sarrazin, Amélie; Thoison, Odile; DuBow, Michael

    2012-01-01

    Degradation of the quorum-sensing (QS) signals known as N-acylhomoserine lactones (AHL) by soil bacteria may be useful as a beneficial trait for protecting crops, such as potato plants, against the worldwide pathogen Pectobacterium. In this work, analytical chemistry and microbial and molecular approaches were combined to explore and compare biostimulation of native and introduced AHL-degrading Rhodococcus erythropolis populations in the rhizosphere of potato plants cultivated in farm greenhouses under hydroponic conditions. We first identified gamma-heptalactone (GHL) as a novel biostimulating agent that efficiently promotes plant root colonization by AHL-degrading R. erythropolis population. We also characterized an AHL-degrading biocontrol R. erythropolis isolate, R138, which was introduced in the potato rhizosphere. Moreover, root colonization by AHL-degrading bacteria receiving different combinations of GHL and R138 treatments was compared by using a cultivation-based approach (percentage of AHL-degrading bacteria), pyrosequencing of PCR-amplified rrs loci (total bacterial community), and quantitative PCR (qPCR) of the qsdA gene, which encodes an AHL lactonase in R. erythropolis. Higher densities of the AHL-degrading R. erythropolis population in the rhizosphere were observed when GHL treatment was associated with biocontrol strain R138. Under this condition, the introduced R. erythropolis population displaced the native R. erythropolis population. Finally, chemical analyses revealed that GHL, gamma-caprolactone (GCL), and their by-products, gamma-hydroxyheptanoic acid and gamma-hydroxycaproic acid, rapidly disappeared from the rhizosphere and did not accumulate in plant tissues. This integrative study highlights biostimulation as a potential innovative approach for improving root colonization by beneficial bacteria. PMID:22081576

  3. Altering plant-microbe interaction through artificially manipulating bacterial quorum sensing.

    PubMed

    Fray, Rupert G

    2002-03-01

    Many bacteria regulate diverse physiological processes in concert with their population size. Bacterial cell-to-cell communication utilizes small diffusible signal molecules, which the bacteria both produce and perceive. The bacteria couple gene expression to cell density by eliciting a response only when the signalling molecules reach a critical threshold (a point at which the population is said to be 'quorate'). The population as a whole is thus able to modify its behaviour as a single unit. Amongst Gram-negative bacteria, the quorum sensing signals most commonly used are N-acylhomoserine lactones (AHLs). It is now apparent that AHLs are used for regulating diverse behaviours in epiphytic, rhizosphere-inhabiting and plant pathogenic bacteria and that plants may produce their own metabolites that interfere with this signalling. Transgenic plants that produce high levels of AHLs or which can degrade bacterial-produced AHLs have been made. These plants have dramatically altered susceptibilities to infection by pathogenic Erwinia species. In addition, such plants will prove useful tools in determining the roles of AHL-regulated density-dependent behaviour in growth promoting, biological control and pathogenic plant-associated bacterial species.

  4. Structure of the Pseudomonas aeruginosa acyl-homoserinelactone synthase LasI.

    PubMed

    Gould, Ty A; Schweizer, Herbert P; Churchill, Mair E A

    2004-08-01

    The LasI/LasR quorum-sensing system plays a pivotal role in virulence gene regulation of the opportunistic human pathogen, Pseudomonas aeruginosa. Here we report the crystal structure of the acyl-homoserine lactone (AHL) synthase LasI that produces 3-oxo-C12-AHL from the substrates 3-oxo-C12-acyl-carrier protein (acyl-ACP) and S-adenosyl-L-methionine. The LasI six-stranded beta sheet platform, buttressed by three alpha helices, forms a V-shaped substrate-binding cleft that leads to a tunnel passing through the enzyme that can accommodate the acyl-chain of acyl-ACP. This tunnel places no apparent restriction on acyl-chain length, in contrast to a restrictive hydrophobic pocket seen in the AHL-synthase EsaI. Interactions of essential conserved N-terminal residues, Arg23, Phe27 and Trp33, suggest that the N-terminus forms an enclosed substrate-binding pocket for S-adenosyl-L-methionine. Analysis of AHL-synthase surface residues identified a binding site for acyl-ACP, a role that was supported by in vivo reporter assay analysis of the mutated residues, including Arg154 and Lys150. This structure and the novel explanation of AHL-synthase acyl-chain-length selectivity promise to guide the design of Pseudomonas aeruginosa-specific quorum-sensing inhibitors as antibacterial agents.

  5. Production of the antifungal compound pyrrolnitrin is quorum sensing-regulated in members of the Burkholderia cepacia complex.

    PubMed

    Schmidt, Silvia; Blom, Judith F; Pernthaler, Jakob; Berg, Gabriele; Baldwin, Adam; Mahenthiralingam, Eshwar; Eberl, Leo

    2009-06-01

    Members of the genus Burkholderia are known for their ability to suppress soil-borne fungal pathogens by the production of various antibiotic compounds. In this study we investigated the role of N-acylhomoserine lactone (AHL)-dependent quorum sensing (QS) in the expression of antifungal traits. Using a quorum quenching approach, that is, by heterologous expression of the Bacillus sp. AiiA lactonase, we show that expression of antifungal activities is AHL-dependent in the large majority of the investigated strains belonging to various Burkholderia species. We demonstrate that in certain strains of Burkholderia ambifaria, Burkholderia pyrrocinia and Burkholderia lata, one of the QS-regulated antifungal agents is pyrrolnitrin (prn), a common broad-spectrum antibiotic that is also produced by some Pseudomonas and Serratia species. To investigate the underlying molecular mechanisms of AHL-dependent prn production in better detail, we inactivated the AHL synthase cepI as well as cepR, which encodes the cognate AHL receptor protein, in B. lata 383. Both QS mutants no longer produced prn as assessed by gas chromatography-mass spectrometry analysis and as a consequence were unable to inhibit growth of Rhizoctonia solani. Using fusions of the lacZ gene to the promoter of the prnABCD operon, which directs the synthesis of prn, we demonstrate that expression of prn is positively regulated by CepR at the level of transcription.

  6. Detection, purification and characterisation of quorum-sensing signal molecules in plant-associated bacteria.

    PubMed

    Brelles-Mariño, G; Bedmar, E J

    2001-10-04

    Quorum sensing (also called autoinduction) is a term that describes an environmental sensing system that allows bacteria to monitor their own population density. Autoinduction relies upon the interaction of a small diffusible signal molecule (the autoinducer) with a transcriptional activator protein to couple gene expression with cell population density. These signal molecules diffuse from bacterial cells and accumulate in the environment as a function of cell growth. Once a threshold concentration is reached, these signals serve as co-inducers to regulate the transcription of (a) set(s) of target genes. In Gram-negative bacteria, most autoinducers belong to the family of N-acylhomoserine lactones (AHLs). The detection of AHLs (or AHL-like activities) has been greatly facilitated by the development of sensitive bioassays that allow fast screening of microorganisms for diffusible signal molecules. AHL or diketopiperazine-mediated cell-cell signalling play roles in regulating different bacterial functions, such as antibiotic biosynthesis, production of virulence factors, exopolysaccharide biosynthesis, bacterial swarming, plasmid conjugal transfer and transition into the stationary phase. Several bacterial species that interact with plants produce AHL-like compounds. In this review, we will summarise the current knowledge about the detection, characterisation and purification of quorum-sensing molecules from plant-associated bacteria. We will also discuss some of the future prospects and biotechnological applications of autoinducers.

  7. An evolving perspective on the Pseudomonas aeruginosa orphan quorum sensing regulator QscR

    PubMed Central

    Chugani, Sudha; Greenberg, Everett P.

    2014-01-01

    Many Proteobacteria govern responses to changes in cell density by using acyl-homoserine lactone (AHL) quorum-sensing (QS) signaling. Similar to the LuxI-LuxR system described in Vibrio fischeri, a minimal AHL QS circuit comprises a pair of genes, a luxI-type synthase gene encoding an enzyme that synthesizes an AHL and a luxR-type AHL-responsive transcription regulator gene. In most bacteria that utilize AHL QS, cognate luxI and luxR homologs are found in proximity to each other on the chromosome. However, a number of recent reports have identified luxR homologs that are not linked to luxI homologs; in some cases luxR homologs have been identified in bacteria that have no luxI homologs. A luxR homolog without a linked luxI homologs is termed an orphan or solo. One of the first reports of an orphan was on QscR in Pseudomonas aeruginosa. The qscR gene was revealed by whole genome sequencing and has been studied in some detail. P. aeruginosa encodes two AHL synthases and three AHL responsive receptors, LasI-LasR form a cognate synthase-receptor pair as do RhlI-RhlR. QscR lacks a linked synthase and responds to the LasI-generated AHL. QS regulation of gene expression in P. aeruginosa employs multiple signals and occurs in the context of other interconnected regulatory circuits that control diverse physiological functions. QscR affects virulence of P. aeruginosa, and although it shows sensitivity to the LasI-generated AHL, 3-oxo-dodecanoylhomoserine lactone, it's specificity is relaxed compared to LasR and can respond equally well to several AHLs. QscR controls a set of genes that overlaps the set regulated by LasR. QscR is comparatively easy to purify and study in vitro, and has become a model for understanding the biochemistry of LuxR homologs. In fact there is a crystal structure of QscR bound to the LasI-generated AHL. Here, we review the current state of research concerning QscR and highlight recent advances in our understanding of its structure and biochemistry

  8. LuxR- and Acyl-Homoserine-Lactone-Controlled Non-lux Genes Define a Quorum-Sensing Regulon in Vibrio fischeri

    PubMed Central

    Callahan, Sean M.; Dunlap, Paul V.

    2000-01-01

    The luminescence (lux) operon (luxICDABEG) of the symbiotic bacterium Vibrio fischeri is regulated by the transcriptional activator LuxR and two acyl-homoserine lactone (acyl-HSL) autoinducers (the luxI-dependent 3-oxo-hexanoyl-HSL [3-oxo-C6-HSL] and the ainS-dependent octanoyl-HSL [C8-HSL]) in a population density-responsive manner called quorum sensing. To identify quorum-sensing-regulated (QSR) proteins different from those encoded by lux genes, we examined the protein patterns of V. fischeri quorum-sensing mutants defective in luxI, ainS, and luxR by two-dimensional polyacrylamide gel electrophoresis. Five non-Lux QSR proteins, QsrP, RibB, AcfA, QsrV, and QSR 7, were identified; their production occurred preferentially at high population density, required both LuxR and 3-oxo-C6-HSL, and was inhibited by C8-HSL at low population density. The genes encoding two of the QSR proteins were characterized: qsrP directs cells to synthesize an apparently novel periplasmic protein, and ribB is a homolog of the Escherichia coli gene for 3,4-dihydroxy-2-butanone 4-phosphate synthase, a key enzyme for riboflavin synthesis. The qsrP and ribB promoter regions each contained a sequence similar to the lux operon lux box, a 20-bp region of dyad symmetry necessary for LuxR/3-oxo-C6-HSL-dependent activation of lux operon transcription. V. fischeri qsrP and ribB mutants exhibited no distinct phenotype in culture. However, a qsrP mutant, in competition with its parent strain, was less successful in colonizing Euprymna scolopes, the symbiotic host of V. fischeri. The newly identified QSR genes, together with the lux operon, define a LuxR/acyl-HSL-responsive quorum-sensing regulon in V. fischeri. PMID:10781550

  9. LuxR- and acyl-homoserine-lactone-controlled non-lux genes define a quorum-sensing regulon in Vibrio fischeri.

    PubMed

    Callahan, S M; Dunlap, P V

    2000-05-01

    The luminescence (lux) operon (luxICDABEG) of the symbiotic bacterium Vibrio fischeri is regulated by the transcriptional activator LuxR and two acyl-homoserine lactone (acyl-HSL) autoinducers (the luxI-dependent 3-oxo-hexanoyl-HSL [3-oxo-C6-HSL] and the ainS-dependent octanoyl-HSL [C8-HSL]) in a population density-responsive manner called quorum sensing. To identify quorum-sensing-regulated (QSR) proteins different from those encoded by lux genes, we examined the protein patterns of V. fischeri quorum-sensing mutants defective in luxI, ainS, and luxR by two-dimensional polyacrylamide gel electrophoresis. Five non-Lux QSR proteins, QsrP, RibB, AcfA, QsrV, and QSR 7, were identified; their production occurred preferentially at high population density, required both LuxR and 3-oxo-C6-HSL, and was inhibited by C8-HSL at low population density. The genes encoding two of the QSR proteins were characterized: qsrP directs cells to synthesize an apparently novel periplasmic protein, and ribB is a homolog of the Escherichia coli gene for 3,4-dihydroxy-2-butanone 4-phosphate synthase, a key enzyme for riboflavin synthesis. The qsrP and ribB promoter regions each contained a sequence similar to the lux operon lux box, a 20-bp region of dyad symmetry necessary for LuxR/3-oxo-C6-HSL-dependent activation of lux operon transcription. V. fischeri qsrP and ribB mutants exhibited no distinct phenotype in culture. However, a qsrP mutant, in competition with its parent strain, was less successful in colonizing Euprymna scolopes, the symbiotic host of V. fischeri. The newly identified QSR genes, together with the lux operon, define a LuxR/acyl-HSL-responsive quorum-sensing regulon in V. fischeri.

  10. Thermochemistry and kinetics of angelica and cognate lactones.

    PubMed

    Wurmel, Judith; Simmie, John M

    2014-06-12

    The enthalpies of formation, bond dissociation energies, ionization potentials, and kinetics of reaction with hydrogen atoms and methyl radicals have been systematically calculated for angelica lactone and a number of related furanones. The objective was to provide comprehensive thermodynamic and kinetic data of compounds that are projected to play a role as intermediates in the production of platform chemicals and biofuels.

  11. Asymmetric gold-catalyzed lactonizations in water at room temperature.

    PubMed

    Handa, Sachin; Lippincott, Daniel J; Aue, Donald H; Lipshutz, Bruce H

    2014-09-26

    Asymmetric gold-catalyzed hydrocarboxylations are reported that show broad substrate scope. The hydrophobic effect associated with in situ-formed aqueous nanomicelles gives good to excellent ee's of product lactones. In-flask product isolation, along with the recycling of the catalyst and the reaction medium, are combined to arrive at an especially environmentally friendly process.

  12. Triacetic acid lactone production in industrial Saccharomyces yeast strains

    USDA-ARS?s Scientific Manuscript database

    Triacetic acid lactone (TAL) is a potential platform chemical that can be produced in yeast. To evaluate the potential for industrial yeast strains to produce TAL, the g2ps1 gene encoding 2-pyrone synthase was transformed into thirteen industrial yeast strains of varied genetic background. TAL produ...

  13. Natural Sesquiterpene Lactones Induce Oxidative Stress in Leishmania mexicana

    PubMed Central

    Barrera, Patricia; Sülsen, Valeria P.; Lozano, Esteban; Rivera, Mónica; Beer, María Florencia; Tonn, Carlos; Martino, Virginia S.; Sosa, Miguel A.

    2013-01-01

    Leishmaniasis is a worldwide parasitic disease, caused by monoflagellate parasites of the genus Leishmania. In the search for more effective agents against these parasites, the identification of molecular targets has been attempted to ensure the efficiency of drugs and to avoid collateral damages on the host's cells. In this work, we have investigated some of the mechanisms of action of a group of natural sesquiterpene lactones that are effective against Leishmania mexicana mexicana promastigotes. We first observed that the antiproliferative effect of mexicanin I (Mxc), dehydroleucodine (DhL), psilostachyin (Psi), and, at lesser extent, psilostachyin C (Psi C) is blocked by 1.5 mM reduced glutathione. The reducing agent was also able to reverse the early effect of the compounds, suggesting that lactones may react with intracellular sulfhydryl groups. Moreover, we have shown that all the sesquiterpene lactones, except Psi C, significantly decreased the endogenous concentration of glutathione within the parasite. Consistent with these findings, the active sesquiterpene lactones increased between 2.7 and 5.4 times the generation of ROS by parasites. These results indicate that the induction of oxidative stress is at least one of the mechanisms of action of DhL, Mxc, and Psi on parasites while Psi C would act by another mechanism. PMID:23861697

  14. Substituted Lactam and Cyclic Azahemiacetals Modulate Pseudomonas aeruginosa Quorum Sensing

    PubMed Central

    Malladi, Venkata L. A.; Sobczak, Adam J.; Maricic, Natalie; Murugapiran, Senthil Kumar; Schneper, Lisa; Makemson, John; Mathee, Kalai; Wnuk, Stanislaw F.

    2011-01-01

    Quorum sensing (QS) is a population-dependent signaling process bacteria use to control multiple processes including virulence that is critical for establishing infection. The most common QS signaling molecule used by Gram-negative bacteria are acylhomoserine lactones. The development of non-native acylhomoserine lactone (AHL) ligands has emerged as a promising new strategy to inhibit QS in Gram-negative bacteria. In this work, we have synthesized a set of optically pure γ-lactams and their reduced cyclic azahemiacetal analogues, bearing the additional alkylthiomethyl substituent, and evaluated their effect on the AHL-dependent Pseudomonas aeruginosa las and rhl QS pathways. The concentration of these ligands and the simple structural modification such as the length of the alkylthio substituent has notable effect on activity. The γ-lactam derivatives with nonylthio or dodecylthio chains acted as inhibitors of las signaling with moderate potency. The cyclic azahemiacetal with shorter propylthio or hexylthio substituent was found to strongly inhibit both las and rhl signaling at higher concentrations while the propylthio analogue strongly stimulated the las QS system at lower concentrations. PMID:21855349

  15. Lactones in 193 nm resists: What do they do?

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Truong, Hoa D.; Brock, Phil J.

    2008-03-01

    Lactones are almost ubiquitously employed in 193 nm resists to increase the polarity of hydrophobic alicyclic polymers. What else do lactones do in 193 nm resists? We studied the behavior of methacrylate (MA) resists consisting of different protecting groups, hexafluoroalcohols, and norbornane lactone methacrylate (NLM, 2-oxo-3-oxatricyclo[4.2.1.04,8]nonan-5-yl methacrylate). When the protecting group is large [ethylcyclooctyl (ECO) and methyladamantyl (MAd)], thinning of the resist film that occurs in highly exposed areas upon postexposure bake (PEB) is significantly smaller than what is expected from the polymer composition. When the concentration of isopropylhexafluoroalcohol methacrylate (iPrHFAMA) is increased in the ECOMA-NLM polymer, the thinning increases and reaches 100% of theory and the ECOMA-norbornenehexafluoroalcohol methacrylate (NBHFAMA) resist loses quantitative thickness in highly-exposed areas upon PEB at 90 °C. This indicates that small lactones which are more basic than esters can trap deprotection fragments especially when the protecting group is large. Such entrapment was detected by IR spectroscopy and also observed at temperatures as high as 200 °C in thermogravimetric analysis (TGA). Incorporation of lactone appears to decrease the bake temperature sensitivity and the sensitivity of the resist perhaps due to trapping of photochemically generated acids by basic lactone. The lactone ring can be hydrolyzed during aqueous base development but does not seem to affect the dissolution rate, indicating that hydrolysis occurs in aqueous base solution after dissolution. Poly(methacrylic acid-NLM) dissolves as fast as poly(methacrylic acid) in 0.26 N tetramethylammonium hydroxide (TMAH) aqueous solution. While exposed P(ECOMA 47-NLM 53) resist dissolves in 0.26 N developer at about the same rate as authentically prepared poly(methacrylic acid 47-NLM 53), the dissolution rate of highly-exposed P(MAdMA 44-NLM 56) resist is much slower, indicating

  16. Chemoenzymatic synthesis and properties of novel lactone-type anionic surfactants.

    PubMed

    Mori, Keisuke; Matsumura, Shuichi

    2012-01-01

    Two series of lactone-type surfactants with and without a hexyl side chain were prepared by the cyclocondensation of dimethyl alkanedioates with unsaturated diols, such as cis-2-butene-1,4-diol and ricinoleyl alcohol, using a lipase, followed by the addition of hydrophilic 3-mercaptopropionic acid in the presence of triethylamine. The lactone-type surfactants showed clear cmc values and surface tension lowering in aqueous solution irrespective of the hexyl side chain. It was found that the cmc values of lactone-type surfactants were lower than that of typical anionics, e.g., sodium laurate, and the cmc value became lower with increasing size of the lactone ring. The adsorption area at the surface of the aqueous lactone-type surfactant solution was larger when compared to the corresponding non-lactone-type surfactants. Lactone-type surfactants without the hexyl side chain aggregated quickly, forming 3-10 nm micelles; on the other hand, lactone-type surfactants with the hexyl side chain formed significantly larger micelles. This is due to the steric hindrance of the hexyl group on the lactone ring. The solubilization ability of the lactone-type surfactants with a hexyl side chain was superior to those without a hexyl side chain. The lactone-type surfactants showed a high foaming power and low foaming stability. They were also biodegraded by activated sludge.

  17. A Novel Metagenomic Short-Chain Dehydrogenase/Reductase Attenuates Pseudomonas aeruginosa Biofilm Formation and Virulence on Caenorhabditis elegans

    PubMed Central

    Bijtenhoorn, Patrick; Mayerhofer, Hubert; Müller-Dieckmann, Jochen; Utpatel, Christian; Schipper, Christina; Hornung, Claudia; Szesny, Matthias; Grond, Stephanie; Thürmer, Andrea; Brzuszkiewicz, Elzbieta; Daniel, Rolf; Dierking, Katja; Schulenburg, Hinrich; Streit, Wolfgang R.

    2011-01-01

    In Pseudomonas aeruginosa, the expression of a number of virulence factors, as well as biofilm formation, are controlled by quorum sensing (QS). N-Acylhomoserine lactones (AHLs) are an important class of signaling molecules involved in bacterial QS and in many pathogenic bacteria infection and host colonization are AHL-dependent. The AHL signaling molecules are subject to inactivation mainly by hydrolases (Enzyme Commission class number EC 3) (i.e. N-acyl-homoserine lactonases and N-acyl-homoserine-lactone acylases). Only little is known on quorum quenching mechanisms of oxidoreductases (EC 1). Here we report on the identification and structural characterization of the first NADP-dependent short-chain dehydrogenase/reductase (SDR) involved in inactivation of N-(3-oxo-dodecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) and derived from a metagenome library. The corresponding gene was isolated from a soil metagenome and designated bpiB09. Heterologous expression and crystallographic studies established BpiB09 as an NADP-dependent reductase. Although AHLs are probably not the native substrate of this metagenome-derived enzyme, its expression in P. aeruginosa PAO1 resulted in significantly reduced pyocyanin production, decreased motility, poor biofilm formation and absent paralysis of Caenorhabditis elegans. Furthermore, a genome-wide transcriptome study suggested that the level of lasI and rhlI transcription together with 36 well known QS regulated genes was significantly (≥10-fold) affected in P. aeruginosa strains expressing the bpiB09 gene in pBBR1MCS-5. Thus AHL oxidoreductases could be considered as potent tools for the development of quorum quenching strategies. PMID:22046268

  18. Perceiving the chemical language of Gram-negative bacteria: listening by high-resolution mass spectrometry.

    PubMed

    Cataldi, Tommaso R I; Bianco, Giuliana; Fonseca, Juliano; Schmitt-Kopplin, Philippe

    2013-01-01

    Gram-negative bacteria use N-acylhomoserine lactones (AHLs) as their command language to coordinate population behavior during invasion and colonization of higher organisms. Although many different bacterial bioreporters are available for AHLs monitoring, in which a phenotypic response, e.g. bioluminescence, violacin production, and β-galactosidase activity, is exploited, mass spectrometry (MS) is the most versatile detector for rapid analysis of AHLs in complex microbial samples, with or without prior separation steps. In this paper we critically review recent advances in the application of high-resolution MS to analysis of the quorum sensing (QS) signaling molecules used by Gram-negative bacteria, with much emphasis on AHLs. A critical review of the use of bioreporters in the study of AHLs is followed by a short methodological survey of the capabilities of high-resolution mass spectrometry (HRMS), including Fourier-transform ion cyclotron resonance (FTICR) MS and quadrupole time-of-flight (qTOF) MS. Use of infusion electrospray ultrahigh-resolution FTICR MS (12 Tesla) enables accurate mass measurements for determination of the elemental formulas of AHLs in Acidovorax sp. N35 and Burkholderia ubonensis AB030584. Results obtained by coupling liquid chromatography with a hybrid quadrupole linear ion trap-FTICR mass spectrometer (LC-LTQ-FTICRMS, 7-T) for characterization of acylated homoserine lactones in the human pathogen Pseudomonas aeruginosa are presented. UPLC-ESI-qTOF MS has also proved to be suitable for identification of 3O-C(10)HSL in Pseudomonas putida IsoF cell culture supernatant. Aspects of sample preparation and the avoidance of analytical pitfalls are also emphasized.

  19. Effects of natural and chemically synthesized furanones on quorum sensing in Chromobacterium violaceum

    PubMed Central

    Martinelli, Daniel; Grossmann, Gilles; Séquin, Urs; Brandl, Helmut; Bachofen, Reinhard

    2004-01-01

    Background Cell to cell signaling systems in Gram-negative bacteria rely on small diffusible molecules such as the N-acylhomoserine lactones (AHL). These compounds are involved in the production of antibiotics, exoenzymes, virulence factors and biofilm formation. They belong to the class of furanone derivatives which are frequently found in nature as pheromones, flavor compounds or secondary metabolites. To obtain more information on the relation between molecular structure and quorum sensing, we tested a variety of natural and chemically synthesized furanones for their ability to interfere with the quorum sensing mechanism using a quantitative bioassay with Chromobacterium violaceum CV026 for antagonistic and agonistic action. We were looking at the following questions: 1. Do these compounds affect growth? 2) Do these compounds activate the quorum sensing system of C. violaceum CV026? 3) Do these compounds inhibit violacein formation induced by the addition of the natural inducer N-hexanoylhomoserine lactone (HHL)? 4) Do these compounds enhance violacein formation in presence of HHL? Results The naturally produced N-acylhomoserine lactones showed a strong non-linear concentration dependent influence on violacein production in C. violaceum with a maximum at 3.7*10-8 M with HHL. Apart from the N-acylhomoserine lactones only one furanone (emoxyfurane) was found to simulate N-acylhomoserine lactone activity and induce violacein formation. The most effective substances acting negatively both on growth and quorum sensing were analogs and intermediates in synthesis of the butenolides from Streptomyces antibioticus. Conclusion As the regulation of many bacterial processes is governed by quorum sensing systems, the finding of natural and synthetic furanones acting as agonists or antagonists suggests an interesting tool to control and handle detrimental AHL induced effects. Some effects are due to general toxicity; others are explained by a competitive interaction for Lux

  20. LuxR solos in Photorhabdus species.

    PubMed

    Brameyer, Sophie; Kresovic, Darko; Bode, Helge B; Heermann, Ralf

    2014-01-01

    Bacteria communicate via small diffusible molecules to mediate group-coordinated behavior, a process designated as quorum sensing. The basic molecular quorum sensing system of Gram-negative bacteria consists of a LuxI-type autoinducer synthase producing acyl-homoserine lactones (AHLs) as signaling molecules, and a LuxR-type receptor detecting the AHLs to control expression of specific genes. However, many proteobacteria possess one or more unpaired LuxR-type receptors that lack a cognate LuxI-like synthase, referred to as LuxR solos. The enteric and insect pathogenic bacteria of the genus Photorhabdus harbor an extraordinarily high number of LuxR solos, more than any other known bacteria, and all lack a LuxI-like synthase. Here, we focus on the presence and the different types of LuxR solos in the three known Photorhabdus species using bioinformatics analyses. Generally, the N-terminal signal-binding domain (SBD) of LuxR-type receptors sensing AHLs have a motif of six conserved amino acids that is important for binding and specificity of the signaling molecule. However, this motif is altered in the majority of the Photorhabdus-specific LuxR solos, suggesting the use of other signaling molecules than AHLs. Furthermore, all Photorhabdus species contain at least one LuxR solo with an intact AHL-binding motif, which might allow the ability to sense AHLs of other bacteria. Moreover, all three species have high AHL-degrading activity caused by the presence of different AHL-lactonases and AHL-acylases, revealing a high quorum quenching activity against other bacteria. However, the majority of the other LuxR solos in Photorhabdus have a N-terminal so-called PAS4-domain instead of an AHL-binding domain, containing different amino acid motifs than the AHL-sensors, which potentially allows the recognition of a highly variable range of signaling molecules that can be sensed apart from AHLs. These PAS4-LuxR solos are proposed to be involved in host sensing, and therefore in

  1. LuxR solos in Photorhabdus species

    PubMed Central

    Brameyer, Sophie; Kresovic, Darko; Bode, Helge B.; Heermann, Ralf

    2014-01-01

    Bacteria communicate via small diffusible molecules to mediate group-coordinated behavior, a process designated as quorum sensing. The basic molecular quorum sensing system of Gram-negative bacteria consists of a LuxI-type autoinducer synthase producing acyl-homoserine lactones (AHLs) as signaling molecules, and a LuxR-type receptor detecting the AHLs to control expression of specific genes. However, many proteobacteria possess one or more unpaired LuxR-type receptors that lack a cognate LuxI-like synthase, referred to as LuxR solos. The enteric and insect pathogenic bacteria of the genus Photorhabdus harbor an extraordinarily high number of LuxR solos, more than any other known bacteria, and all lack a LuxI-like synthase. Here, we focus on the presence and the different types of LuxR solos in the three known Photorhabdus species using bioinformatics analyses. Generally, the N-terminal signal-binding domain (SBD) of LuxR-type receptors sensing AHLs have a motif of six conserved amino acids that is important for binding and specificity of the signaling molecule. However, this motif is altered in the majority of the Photorhabdus-specific LuxR solos, suggesting the use of other signaling molecules than AHLs. Furthermore, all Photorhabdus species contain at least one LuxR solo with an intact AHL-binding motif, which might allow the ability to sense AHLs of other bacteria. Moreover, all three species have high AHL-degrading activity caused by the presence of different AHL-lactonases and AHL-acylases, revealing a high quorum quenching activity against other bacteria. However, the majority of the other LuxR solos in Photorhabdus have a N-terminal so-called PAS4-domain instead of an AHL-binding domain, containing different amino acid motifs than the AHL-sensors, which potentially allows the recognition of a highly variable range of signaling molecules that can be sensed apart from AHLs. These PAS4-LuxR solos are proposed to be involved in host sensing, and therefore in

  2. Biosynthesis of resorcylic acid lactone lasiodiplodin in Lasiodiplodia theobromae.

    PubMed

    Kashima, Takasumi; Takahashi, Kosaku; Matsuura, Hideyuki; Nabeta, Kensuke

    2009-05-01

    The biosynthesis of lasiodiplodin (1) and its (5S)-5-hydroxylated derivative (2) were investigated by the administration of (13)C-labeled acetates to Lasiodiplodia theobromae. The labeling patterns of biosynthetically (13)C-labeled 1 and 2 were determined by (13)C-NMR and INADEQUATE spectra, demonstrating the octaketide origins of 1 and 2. Taking into account the biosynthetic study of resorcylic acid lactones, the involvement of highly reduced acyl intermediates in the biosynthesis of lasiodiplodins was presumed; thus, we synthesized (2)H-labeled hypothetical acyl intermediates of 1, 9-hydroxydecanoic acid (4) and its N-acetylcysteamine thioester (SNAC, 5). When L. theobromae was incubated with 5 mM of a (2)H-labeled intermediate, the (2)H-label from the intermediate was incorporated at the expected position of 1. These incorporation studies revealed that 1 was produced via a pathway which closely resembles that of resorcylic acid lactone biosynthesis.

  3. Lactonic Sophorolipids Increase Tumor Burden in Apcmin+/- Mice

    PubMed Central

    Callaghan, Breedge; Lydon, Helen; Roelants, Sophie L. K. W.; Van Bogaert, Inge N. A.; Marchant, Roger; Banat, Ibrahim M.; Mitchell, Christopher A.

    2016-01-01

    Sophorolipids (SL) are amphiphilic biosurfactant molecules consisting of a disaccharide sophorose with one fatty acid at the C1 position and optional acetylation at the C6’and C6” positions. They exist in a closed ring lactonic (LSL) or open acidic (ASL) structure Sophorolipids are produced in crude mixtures in economically viable amounts by the yeast Starmerella bombicola and used in a variety of consumer products. Varying levels of anti- proliferative and anti-cancer activity of crude sophorolipid mixtures are described in a number of tumor cell lines in vitro. However, significant inter-study variation exists in the composition of sophorolipid species as well as other biologically active compounds in these mixtures, which makes interpretation of in vitro and in vivo studies difficult. We produced a 96% pure C18:1 lactonic sophorolipid that dose-dependently reduces the viability of colorectal cancer, as well as normal human colonic and lung cell lines in vitro. Oral administration of vehicle-only; or lactonic sophorolipids (50 mg/kg for 70 days), to Apcmin+/- mice resulted in an increase in the number (55.5 ± 3.3 vs 70.50 ± 7.8: p < 0.05) and size (modal size 2mm vs 4mm) of intestinal polyps. Lactonic administration resulted in a systematic effect via reduced hematocrit (49.5 ± 1.0 vs 28.2 ± 2.0 vs: p<0.03) and splenomegaly (0.56 ± 0.03g vs 0.71 ± 0.04g; p<0.01) confirming exacerbation of disease progression in this model. PMID:27271048

  4. A kinetic approach to the alkylating potential of carcinogenic lactones.

    PubMed

    Manso, José A; Pérez-Prior, M Teresa; García-Santos, M del Pilar; Calle, Emilio; Casado, Julio

    2005-07-01

    The alkylating potential of beta-propiolactone (BPL), beta-butyrolactone (BBL), gamma-butyrolactone, and delta-valerolactone, which can be formed by the in vivo nitrosation of primary amino acids, was investigated kinetically. The nucleophile NBP, 4-(p-nitrobenzyl)pyridine, a trap for alkylating agents, was used as an alkylation substrate. The alkylation reactions were performed under mimicked cellular conditions at neutral pH in water/dioxane solvent mixtures. To gain insight into the effect of the hydrolysis of lactones on their alkylating efficiency, alkylation and competing hydrolysis were studied in parallel. Conclusions were drawn as follows: (i) gamma-Butyrolactone and delta-valerolactone afford neither appreciable NBP alkylation nor hydrolysis reactions; (ii) the alkylating potential of BPL is 10-fold higher than that of BBL, the reactivity of both being essentially enthalpy-controlled; (iii) a correlation was found between the alkylating potential of lactones and their carcinogenicity; (iv) the hydrolysis of lactones is not sufficiently effective to prevent alkylation; (v) the efficiency of alkylation, expressed as the alkylation rate/hydrolysis rate ratio, decreases strongly with increasing amounts of dioxane in the reaction media; (vi) the absorption coefficients of the NBP-lactone adducts are as follows: epsilon(NBP-BPL) = 5101 +/- 111 M(-1) cm(-1) (lambda = 584 nm) and epsilon(NBP-BBL) = 462 +/- 19 M(-1) cm(-1) (lambda = 586 nm), the pronounced difference between these values being rationalized in terms of the adducts' structure; and (vii) linear correlations exist between the adducts' absorption coefficients and the water/dioxane ratio in the reaction media.

  5. Molluscicidal sesquiterpene lactones from species of the tribe Vernonieae (Compositae).

    PubMed

    Borkosky, Susana; Ponce de León, Susana; Juárez, Gabriela; Sierra, Manuel González; Bardón, Alicia

    2009-04-01

    Schistosomiasis is caused by parasitic flatworms of the genus Schistosoma, and some snails, particularly of the genus Biomphalaria (Planorbidae), are directly implicated in the transmission of the disease. Continuing with our investigations of bioactive plant constituents, we evaluated and report in the present article, the molluscicidal effects of 16 sesquiterpene lactones, as well as the commercial reagents tetrahydrofuran, furfural, and furfuryl alcohol, on an adult population of B. peregrina. The natural sesquiterpene lactones tested are characteristic constituents of species of the tribe Vernonieae, family Asteraceae. Compounds 1-3 and 7 came from a Bolivian collection of Vernonanthura pinguis, compounds 4 and 5 from an Argentine collection of Cyrtocymura cincta var. cincta, 6 was obtained from a Bolivian collection of Eirmocephala megaphylla, 8-14 from an Argentine collection of Centratherum punctatum ssp. punctatum, and compounds 15 and 16 were obtained by chemical derivatization from 5 and 14, respectively. Ten of the sesquiterpene lactones displayed moderate molluscicidal activity (LD50<100 microg/ml). Commercial reagents were inactive.

  6. Paper strip whole cell biosensors: a portable test for the semiquantitative detection of bacterial quorum signaling molecules.

    PubMed

    Struss, Anjali; Pasini, Patrizia; Ensor, C Mark; Raut, Nilesh; Daunert, Sylvia

    2010-06-01

    Herein, we report the development of a novel, inexpensive, and portable filter-paper-based strip biosensor for the detection of bacterial quorum sensing signaling molecules, N-acylhomoserine lactones (AHLs). AHLs are generally employed by Gram-negative bacteria for their cell-cell communication to control expression of specialized genes, such as those involved in biofilm formation and production of virulence factors, in a population-density-dependent manner. First, a bacterial cell-based sensing system employing components of AHL-mediated QS regulatory system as recognition elements and beta-galactosidase as the reporter protein was designed and developed. The bacterial-sensing cells were then liquid-dried on strips of filter paper. beta-Galactosidase as the reporter allows for the visual monitoring of the analyte-induced signal when a colorimetric method of detection is applied. The paper strip biosensor was able to detect low AHL concentrations down to 1 x 10(-8) M. Furthermore, it was successfully applied to the detection of AHLs in physiological samples, such as saliva. The filter-paper-based sensing strips could provide reproducible results upon storage at 4 degrees C for at least 3 months. In conclusion, a filter-paper-based strip biosensor was developed that allows for visual, fast, and convenient detection of AHLs in a dose-dependent manner in a test sample. In addition, it does not require expensive equipment or trained personnel and allows ease of transportation and storage. Therefore, we envision that this biosensor will serve as a simple and economical portable field kit for on-site monitoring of AHL in a variety of clinical and environmental samples.

  7. A complex LuxR-LuxI type quorum sensing network in a roseobacterial marine sponge symbiont activates flagellar motility and inhibits biofilm formation.

    PubMed

    Zan, Jindong; Cicirelli, Elisha M; Mohamed, Naglaa M; Sibhatu, Hiruy; Kroll, Stephanie; Choi, Okhee; Choi, Ohkee; Uhlson, Charis L; Wysoczynski, Christina L; Wysoczinski, Christina L; Murphy, Robert C; Churchill, Mair E A; Hill, Russell T; Fuqua, Clay

    2012-09-01

    Bacteria isolated from marine sponges, including the Silicibacter-Ruegeria (SR) subgroup of the Roseobacter clade, produce N-acylhomoserine lactone (AHL) quorum sensing signal molecules. This study is the first detailed analysis of AHL quorum sensing in sponge-associated bacteria, specifically Ruegeria sp. KLH11, from the sponge Mycale laxissima. Two pairs of luxR and luxI homologues and one solo luxI homologue were identified and designated ssaRI, ssbRI and sscI (sponge-associated symbiont locus A, B and C, luxR or luxI homologue). SsaI produced predominantly long-chain 3-oxo-AHLs and both SsbI and SscI specified 3-OH-AHLs. Addition of exogenous AHLs to KLH11 increased the expression of ssaI but not ssaR, ssbI or ssbR, and genetic analyses revealed a complex interconnected arrangement between SsaRI and SsbRI systems. Interestingly, flagellar motility was abolished in the ssaI and ssaR mutants, with the flagellar biosynthesis genes under strict SsaRI control, and active motility only at high culture density. Conversely, ssaI and ssaR mutants formed more robust biofilms than wild-type KLH11. AHLs and the ssaI transcript were detected in M. laxissima extracts, suggesting that AHL signalling contributes to the decision between motility and sessility and that it may also facilitate acclimation to different environments that include the sponge host. © 2012 Blackwell Publishing Ltd.

  8. A Complex LuxR-LuxI Type Quorum Sensing Network in a Roseobacterial Marine Sponge Symbiont Activates Flagellar Motility and Inhibits Biofilm Formation

    PubMed Central

    Zan, Jindong; Cicirelli, Elisha M.; Mohamed, Naglaa M.; Sibhatu, Hiruy; Kroll, Stephanie; Choi, Ohkee; Uhlson, Charis L.; Wysoczinski, Christina L.; Murphy, Robert C.; Churchill, Mair E.A.; Hill, Russell T.; Fuqua, Clay

    2012-01-01

    Summary Bacteria isolated from marine sponges, including the Silicibacter-Ruegeria (SR) subgroup of the Roseobacter clade, produce N-acylhomoserine lactone (AHL) quorum sensing signal molecules. This study is the first detailed analysis of AHL quorum sensing in sponge-associated bacteria, specifically Ruegeria sp. KLH11, from the sponge Mycale laxissima. Two pairs of luxR and luxI homologues and one solo luxI homologue were identified and designated ssaRI, ssbRI, and sscI (sponge-associated symbiont locus A, B, and C, luxRI or luxI homologue). SsaI produced predominantly long-chain 3-oxo-AHLs and both SsbI and SscI specified 3-OH-AHLs. Addition of exogenous AHLs to KLH11 increased the expression of ssaI but not ssaR, ssbI or ssbR, and genetic analyses revealed a complex interconnected arrangement between SsaRI and SsbRI systems. Interestingly, flagellar motility was abolished in the ssaI and ssaR mutants, with the flagellar biosynthesis genes under strict SsaRI control, and active motility only at high culture density. Conversely, ssaI and ssaR mutants formed more robust biofilms than wild type KLH11. AHLs and transcript of the ssaI gene were detected in M. laxissima extracts suggesting that AHL signaling contributes to the decision between motility and sessility and that it also may facilitate acclimation to different environments including the sponge host. PMID:22742196

  9. Human serum paraoxonase (PON1) isozymes Q and R hydrolyze lactones and cyclic carbonate esters.

    PubMed

    Billecke, S; Draganov, D; Counsell, R; Stetson, P; Watson, C; Hsu, C; La Du, B N

    2000-11-01

    It is well established that human serum paraoxonase (PON1) catalyzes the hydrolysis of organophosphate insecticides and nerve agents, as well as that of a number of aromatic carboxylic acid esters. Our laboratory has recently found a new class of PON1 substrates that includes at least 30 lactones and cyclic carbonate esters. The lactone substrates vary in their ring size from 4 to 7 atoms. Substituents on the ring carbons may enhance or reduce the rate of lactone hydrolysis. An appreciable degree of stereospecificity exists with some activities differing up to 9-fold between enantiomers (i.e., S-alpha-hydroxy-gamma-butyrolactone is hydrolyzed 5 to 9 times faster than the R form). Thiolactones are hydrolyzed less efficiently, and some lactams are potent inhibitors. Four lactone-containing drugs-spironolactone, mevastatin, simvastatin, and lovastatin-have been identified as substrates for PON1. All lactone substrates are hydrolyzed by both the Q and R isozymes of human serum PON1. However, some lactone substrates are hydrolyzed faster by the Q than R isozyme, whereas others show a reverse preference. Moreover, these new substrates include homogentisic acid lactone, mevalonic acid lactone, homocysteine thiolactone, and gamma-hydroxybutyric acid lactone-all lactone forms of endogenous compounds. It is reasonable to expect that further investigations may uncover PON1 lactone substrates that are, themselves, endogenous compounds. In this article we characterize the basic enzymatic properties of PON1's newly identified hydrolytic activities with lactone and cyclic carbonate ester substrates and compare these properties with those of representative arylesters and organophosphates.

  10. Kinetics of lactone hydrolysis in antitumor drugs of camptothecin series as studied by fluorescence spectroscopy.

    PubMed

    Chourpa, I; Millot, J M; Sockalingum, G D; Riou, J F; Manfait, M

    1998-03-02

    Potent antitumor activity exhibited by 20-S-camptothecin (CPT) and numerous derivatives is known to be lost upon opening of the alpha-hydroxy-lactone ring of these drugs, hydrolyzable at neutral and basic pH. To quantify in 'real time' the lactone hydrolysis reaction in CPTs under physiological conditions, we have applied a non-perturbing approach by fluorescence spectroscopy. CPT and a set of its derivatives (21-lactam-S-CPT, 10,11-(methylenedioxy)-CPT, CPT-11, SN-38, topotecan, tricyclic ketone-CPT) with antitumor activity varying from negligible to 10 times that of CPT have been studied. Prior to the kinetic measurements, the effects of substitutions, pH, polarity of molecular environment, lactone ring opening (lactone-carboxylate transition) have been investigated in terms of the UV-visible absorption and fluorescence emission spectra of CPTs. Then the determined parameters of the fluorescence emission spectra corresponding to the respective lactone and carboxylate forms have been used to estimate the residual lactone percentage as a function of time. The reproducibility of the obtained data demonstrates that the spectroscopic approach provides a satisfactory precision for this kind of measurements. For CPT at pH 7.3, the lactone half-life was 29.4 +/- 1.7 min and the lactone percentage at equilibrium was 20.9 +/- 0.3%. Within a series of derivatives with substitutions at quinoline rings, the lactone half-life varied from 29 to 32 min and the equilibrium lactone content varied from 15% to 23%. For each compound, even slight increase of pH from 7.1 to 7.3 or from 7.3 to 7.6 logically leads to a remarkable decrease of both lactone half-life and equilibrium lactone percentage.

  11. The fumigant and repellent activity of aliphatic lactones against Pediculus humanus capitis (Anoplura: Pediculidae).

    PubMed

    Toloza, Ariel Ceferino; Zygadlo, Julio; Mougabure-Cueto, Gastón; Zerba, Eduardo; Faillaci, Silvina; Picollo, María Inés

    2006-02-01

    New alternative insecticides are necessary for the chemical control of head lice. In this study the fumigant knockdown time 50% (KT50) and repellency index (RI) of three aliphatic lactones was compared with two essential oils and DDVP, against permethrin-resistance Pediculus humanus capitis from Argentina. In the fumigant assay, none of the lactones were effective compared to the highest activity of eucalyptus (KT50 15.53 m). In the repellency test, the three lactones were equally or more effective (RI ranging from 60.50 to 76.68) than the positive control (piperonal). These lactones are promising as head lice repellents.

  12. [Feverfew lactone induces autophagic death of hepatocellular carcinoma SMMC 7721 cells].

    PubMed

    Liu, Zhan-Pei; Li, Yan-Yan; Gao, Bo; Li, Jun; Gao, Jun-Ping; Lin, Ping

    2014-07-01

    To explore the effect and mechanism of feverfew lactone on inducing autophagic death of hepatocellular carcinoma. The proliferation of hepatocellular carcinoma SMMC 7721 cells treated with feverfew lactone was measured by MTT assay. The autophagy of SMMC 7721 induced with feverfew lactone was assessed by acridine orange staining, autophagic marker LC3 and p62 detecting and autophagic flows analyzing. In addition, a role of ROS in this process was stated by treatment with antioxidant agent N-acetyl-L-cysteine (NAC). The proliferation of SMMC 7721 cells were inhibited by feverfew lactone in a concentration dependence manner. The expression of LC3 and autophagic flows of SMMC 7721 cells were increased by feverfew lactone, while p62 was decreased, which implied that feverfew lactone could induce the autophagy of SMMC 7721 cells. Further more, the autophagy effect induced by feverfew lactone was declined obviously when treated with NAC suggested that ROS played an important role in this effect. Feverfew lactone induces autophagic death of SMMC 7721 cells by stimulating cells to produce ROS. The study will be helpful for the treatment of hepatocellular carcinoma and to provide theoretical basis for the clinical application of feverfew lactone.

  13. Metabolism of 4-Hydroxy-7-oxo-5-heptenoic Acid (HOHA) Lactone by Retinal Pigmented Epithelial Cells.

    PubMed

    Wang, Hua; Linetsky, Mikhail; Guo, Junhong; Yu, Annabelle O; Salomon, Robert G

    2016-07-18

    4-Hydroxy-7-oxo-5-heptenic acid (HOHA)-lactone is a biologically active oxidative truncation product released (t1/2 = 30 min at 37 °C) by nonenzymatic transesterification/deacylation from docosahexaenoate lipids. We now report that HOHA-lactone readily diffuses into retinal pigmented epithelial (RPE) cells where it is metabolized. A reduced glutathione (GSH) Michael adduct of HOHA-lactone is the most prominent metabolite detected by LC-MS in both the extracellular medium and cell lysates. This molecule appeared inside of ARPE-19 cells within seconds after exposure to HOHA-lactone. The intracellular level reached a maximum concentration at 30 min and then decreased with concomitant increases in its level in the extracellular medium, thus revealing a unidirectional export of the reduced GSH-HOHA-lactone adduct from the cytosol to extracellular medium. This metabolism is likely to modulate the involvement of HOHA-lactone in the pathogenesis of human diseases. HOHA-lactone is biologically active, e.g., low concentrations (0.1-1 μM) induce secretion of vascular endothelial growth factor (VEGF) from ARPE-19 cells. HOHA-lactone is also a precursor of 2-(ω-carboxyethyl)pyrrole (CEP) derivatives of primary amino groups in proteins and ethanolamine phospholipids that have significant pathological and physiological relevance to age-related macular degeneration (AMD), cancer, and wound healing. Both HOHA-lactone and the derived CEP can contribute to the angiogenesis that defines the neovascular "wet" form of AMD and that promotes the growth of tumors. While GSH depletion can increase the lethality of radiotherapy, because it will impair the metabolism of HOHA-lactone, the present study suggests that GSH depletion will also increase levels of HOHA-lactone and CEP that may promote recurrence of tumor growth.

  14. Deducing receptor signaling parameters from in vivo analysis: LuxN/AI-1 quorum sensing in Vibrio harveyi

    PubMed Central

    Swem, Lee R.; Swem, Danielle L.; Wingreen, Ned S.; Bassler, Bonnie L.

    2008-01-01

    Summary Quorum sensing, a process of bacterial cell-cell communication, relies on production, detection, and response to autoinducer signaling molecules. Here we focus on LuxN, a nine transmembrane domain protein from Vibrio harveyi, and the founding example of membrane-bound receptors for acyl-homoserine lactone (AHL) autoinducers. Previously, nothing was known about signal recognition by membrane-bound AHL receptors. We used mutagenesis and suppressor analyses to identify the AHL-binding domain of LuxN, and discovered LuxN mutants that confer decreased and increased AHL sensitivity. Our analysis of dose-response curves of multiple LuxN mutants pins these inverse phenotypes on quantifiable opposing shifts in the free-energy bias of LuxN for its kinase and phosphatase states. To extract signaling parameters, we exploited a strong LuxN antagonist, one of fifteen small-molecule antagonists we identified. We find that quorum-sensing-mediated communication can be manipulated positively and negatively to control bacterial behavior, and that signaling parameters can be deduced from in vivo data. PMID:18692469

  15. Antibiotic resistome promotion in drinking water during biological activated carbon treatment: Is it influenced by quorum sensing?

    PubMed

    Zheng, Ji; Chen, Tao; Chen, Hong

    2017-08-24

    The contamination of antibiotic resistance genes (ARGs) in drinking water may pose a direct threat to human health. This study applied high-throughput qPCR and sequencing to investigate the dynamics of ARGs and bacterial communities during the advanced treatment of drinking water using biological activated carbon. The promotion of ARGs was observed, and the normalized copy number of ARGs increased significantly after BAC treatment, raising the number of detected ARGs from 84 to 159. Twenty-nine ARGs were identified as biofilm-influencing sources in the BAC, and they persisted after chlorination. The shift of bacterial communities primarily had effects on the changes in resistome. Firmicutes, Cyanobacteria were related to persistent ARGs mostly in the BAC biofilm. Meanwhile, the Acyl-Homoserine Lactones (AHLs), quorum sensing molecules, and bacteria that produced AHLs were identified to understand the promotion of ARGs. The isolated AHL-producing bacteria belonged to the Proteobacteria, Firmicutes and Bacteroidetes phyla. Six detectable AHLs had an influence on plasmid-based horizontal gene transfer in the intragenus mating systems, indicating that the dynamics of ARGs were strongly affected by quorum sensing between specific bacteria in the biofilm. These results provide new insight into the mechanism of antibiotic resistome promotion in BAC biofilms. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Cranberry-derived proanthocyanidins impair virulence and inhibit quorum sensing of Pseudomonas aeruginosa

    PubMed Central

    Maisuria, Vimal B.; Los Santos, Yossef Lopez-de; Tufenkji, Nathalie; Déziel, Eric

    2016-01-01

    Bacteria have evolved multiple strategies for causing infections that include producing virulence factors, undertaking motility, developing biofilms, and invading host cells. N-acylhomoserine lactone (AHL)-mediated quorum sensing (QS) tightly regulates the expression of multiple virulence factors in the opportunistic pathogenic bacterium Pseudomonas aeruginosa. Thus, inhibiting QS could lead to health benefits. In this study, we demonstrate an anti-virulence activity of a cranberry extract rich in proanthocyanidins (cerPAC) against P. aeruginosa in the model host Drosophila melanogaster and show this is mediated by QS interference. cerPAC reduced the production of QS-regulated virulence determinants and protected D. melanogaster from fatal infection by P. aeruginosa PA14. Quantification of AHL production using liquid chromatography-mass spectrometry confirmed that cerPAC effectively reduced the level of AHLs produced by the bacteria. Furthermore, monitoring QS signaling gene expression revealed that AHL synthases LasI/RhlI and QS transcriptional regulators LasR/RhlR genes were inhibited and antagonized, respectively, by cerPAC. Molecular docking studies suggest that cranberry-derived proanthocyanidin binds to QS transcriptional regulators, mainly interacting with their ligand binding sites. These findings provide insights into the underlying mechanisms of action of a cerPAC to restrict the virulence of P. aeruginosa and can have implications in the development of alternative approaches to control infections. PMID:27503003

  17. Cloning and expression of quorum sensing N-acyl-homoserine synthase (LuxI) gene detected in Acinetobacter baumannii

    PubMed Central

    Modarresi, Farzan; Azizi, Omid; Shakibaie, Mohammad Reza; Motamedifar, Mohammad; Mansouri, Shahla

    2016-01-01

    Background and Objectives: In present study we aimed to clone the luxI gene encoding N-acyl-homoserine synthase detected in clinical isolates of Acinetobacter baumannii and study its expression in Escherichia coli transformants. Materials and Methods: Four A. baumannii hospital strains which demonstrated strong biofilm activity were selected in this investigation. The presence of luxI gene was detected using PCR technique. Purified PCR product DNA was initially cloned into pTG19 and transformed to E. coli DH5α. The gene was then recovered from agarose gel and ligated by T4 DNA ligase into pET28a expression vector using NdeI and XhoI enzymes. pET28a + luxI was transformed into E. coli BL21 (DE3). The luxI putative gene was further detected in the transformants by colony PCR. Expression of the luxI gene in the recombinant E. coli BL21 cells was studied by quantitative real time PCR (qRT-PCR) and the presence of N-acylhomoserine lactone (AHL) was checked by colorimetric assay and Fourier Transform Infra-Red (FT-IR) spectroscopy. Results: We successfully cloned AHL gene from A. baumannii strain 23 to pET28a expression vector. There was four fold increases in expression of luxI in the transformants (P ≤ 0.05). It was found that, strain 23 and the transformants showed highest amount of AHL activity (OD = 1.524). The FT-IR analysis indicated stretching C=O bond of the lactone ring and primary amides (N=H) at 1764.69 cm−1 and 1659.23 cm−1 respectively. Conclusion: From above results we concluded that, luxI in A. baumannii is indeed responsible for AHL production and not regulation and pET28a vector allows efficient AHL expression in E. coli BL21 transformants. PMID:27307980

  18. Macrocyclic lactone anthelmintics: spectrum of activity and mechanism of action.

    PubMed

    Geary, Timothy G; Moreno, Yovany

    2012-05-01

    Macrocyclic lactones (MLs), exemplified by the prototype of the class, ivermectin (IVM), are mainstays of programs for the control of nematode and arthropod parasites and pests. Since their introduction 30 years ago, research has revealed that they act on a family of ligand-gated chloride channels gated by glutamate, which is largely restricted to animals in the phyla Nematoda and Arthropoda. Studies on IVM in model organisms have contributed greatly to our understanding of ML pharmacology, but our understanding of the basis for differences among species and among MLs in potency and spectrum remains far from complete.

  19. Two new sesquiterpene lactones from Montanoa tomentosa ssp. microcephala.

    PubMed

    Braca, A; Cioffi, G; Morelli, I; Venturella, F; Pizza, C; De Tommasi, N

    2001-11-01

    Two new sesquiterpene lactones: 8alpha-(4'-acetoxymethacryloyloxy)-3alpha,9beta-dihydroxy-1(10)E,4Z,11(13)-germacratrien-12,6alpha-olide (1) and 8alpha-(2'E)-(2'-acetoxymethyl-2'-butenoyloxy)-3alpha,9beta-dihydroxy-1(10)E,4Z,11(13)-germacratrien-12,6alphaolide (2), together with the known zoapatanolide A were isolated from the aerial parts of Montanoa tomentosa Cerv. in La Llave et Lex ssp. microcephala (Sch. Bip. In K. Koch) V.A. Funk (Asteraceae). The structures of all compounds were established on the basis of 1D, 2D NMR, and EIMS analysis.

  20. Sesquiterpene lactone composition of wild and cultivated sunflowers and biological activity against an insect pest

    USDA-ARS?s Scientific Manuscript database

    Sesquiterpene lactones in sunflowers, Helianthus spp., are important to interactions with pathogens, weeds and insects. Across a broad range of H. annuus, differences in composition of sesquiterpene lactones extracted from florets were found between wild and cultivated sunflowers, but also between d...

  1. A new sesquiterpene lactone with sulfonic acid group from Saussurea lappa.

    PubMed

    Yin, Hong-Quan; Hua, Hui-Ming; Fu, Hong-Wei; Qi, Xiu-Lan; Li, Wen; Sha, Yi; Pei, Yue-Hu

    2007-01-01

    A new sesquiterpene lactone with an unusual sulfonic acid group, 13-sulfo-dihydrodehydrocostus lactone (1), was isolated from the roots of Saussurea lappa C. (Compositae), together with a known lignan (2). The structure of 1 was characterized on the basis of spectral evidence including 2DNMR studies. Compound 2 was obtained from this plant for the first time.

  2. Identifying lactone hydrolysis in pharmaceuticals. A tool for metabolite structural characterization.

    PubMed

    Yi, Lin; Bandu, Mary L; Desaire, Heather

    2005-10-15

    Methods to characterize metabolic transformations in a rapid and reliable fashion are required for facilitating the development of all new pharmaceuticals. One metabolic transformation, which is the focus of this study, is lactone hydrolysis. For pharmaceuticals containing lactones, hydrolysis occurs readily due to both enzymatic and nonenzymatic processes. Hydrolysis affects both the bioavailability and the efficacy of lactone-containing drugs and pro-drugs. To facilitate the characterization of lactones and their corresponding hydrolysis products, we have developed a mass spectrometric method that can readily discriminate between a lactone and its corresponding carboxylic acid, even when these changes are accompanied by other modifications that occur during metabolism. This method uses characteristic product ions in MS/MS experiments, and the trends described herein can be applied broadly to several types of lactones. To demonstrate the efficacy of this approach, two different lactones that had undergone multiple modifications were characterized, and in both cases, lactone hydrolysis was readily discernible, based on the MS/MS data.

  3. Piperitone-derived saturated lactones: synthesis and aphid behavior-modifying activity.

    PubMed

    Grudniewska, Aleksandra; Dancewicz, Katarzyna; Białońska, Agata; Wawrzeńczyk, Czesław; Gabryś, Beata

    2013-04-10

    Two racemic and two enantiomeric pairs of new saturated lactones with the p-menthane system were obtained. The lactones were synthesized from racemic and enantiomerically enriched cis- and trans-piperitols, which were obtained from piperitone. The structures of the compounds were confirmed by spectroscopic data. The antifeedant activity of piperitone to Myzus persicae was studied, and the biological consequences of structural modifications of piperitone, that is, lactonization and chiral center configuration, were examined as well. The behavioral responses of M. persicae to piperitone and piperitone-derived saturated lactones were investigated to reveal the biological background of their deterrent activity. Piperitone appeared rather neutral or weakly deterrent to aphids. The introduction of a lactone moiety into a piperitone molecule dramatically changed its biological activity. All piperitone-derived lactones evoked negative aphid responses. However, the deterrent activity of individual compounds varied in potency, the time of expression, and the duration of the effect, depending on the spatial structure of the lactone. Lactones (1R,3S,6R)-3-isopropyl-6-methyl-9-oxabicyclo[4.3.0]nonan-8-one and trans-3-isopropyl-6-methyl-9-oxabicyclo[4.3.0]nonan-8-one showed the broadest ranges and the highest potencies and durabilities of deterrent activity to M. persicae: they acted immediately after application, caused a cessation of probing before aphids reached phloem elements, and decreased the quality of phloem sap.

  4. Non-native acylated homoserine lactones reveal that LuxIR quorum sensing promotes symbiont stability.

    PubMed

    Studer, Sarah V; Schwartzman, Julia A; Ho, Jessica S; Geske, Grant D; Blackwell, Helen E; Ruby, Edward G

    2014-08-01

    Quorum sensing, a group behaviour coordinated by a diffusible pheromone signal and a cognate receptor, is typical of bacteria that form symbioses with plants and animals. LuxIR-type N-acyl L-homoserine (AHL) quorum sensing is common in Gram-negative Proteobacteria, and many members of this group have additional quorum-sensing networks. The bioluminescent symbiont Vibrio fischeri encodes two AHL signal synthases: AinS and LuxI. AinS-dependent quorum sensing converges with LuxI-dependent quorum sensing at the LuxR regulatory element. Both AinS- and LuxI-mediated signalling are required for efficient and persistent colonization of the squid host, Euprymna scolopes. The basis of the mutualism is symbiont bioluminescence, which is regulated by both LuxI- and AinS-dependent quorum sensing, and is essential for maintaining a colonization of the host. Here, we used chemical and genetic approaches to probe the dynamics of LuxI- and AinS-mediated regulation of bioluminescence during symbiosis. We demonstrate that both native AHLs and non-native AHL analogues can be used to non-invasively and specifically modulate induction of symbiotic bioluminescence via LuxI-dependent quorum sensing. Our data suggest that the first day of colonization, during which symbiont bioluminescence is induced by LuxIR, is a critical period that determines the stability of the V. fischeri population once symbiosis is established.

  5. Membrane-Surface Anchoring of Charged Diacylglycerol-Lactones Correlates with Biological Activities | Center for Cancer Research

    Cancer.gov

    The inside cover picture shows the molecular structure of a DAG lactone derivative on top of the inner leaflet of a DMPC bilayer. The confocal microscopy image illustrates DAG-lactone-stimulated membrane localization of PKCδ-ECFP in living cells, while the space-filling model shows the surface of the C1B domain of PKCδ, the target of the lactone.

  6. Radical photocyclization route for macrocyclic lactone ring expansion and conversion to macrocyclic lactams and ketones.

    PubMed

    Nishikawa, Keisuke; Yoshimi, Yasuharu; Maeda, Kousuke; Morita, Toshio; Takahashi, Ichiro; Itou, Tatsuya; Inagaki, Sho; Hatanaka, Minoru

    2013-01-18

    A new method for the synthesis of macrocyclic lactones, lactams, and ketones, which utilizes photoinduced intramolecular radical cyclization reactions of substrates containing tethered carboxylic acids and α,β-unsaturated carbonyl moieties, has been uncovered. Photocyclization of the carboxylic acids tethered acrylate ester, which were prepared starting from the macrocyclic lactones, gave the two-carbon elongated macrocyclic lactones via decarboxylation. Similar photoreactions of carboxylic acid tethered acryl amide or α,β-unsaturated ketone moieties, which were also prepared starting from the macrocyclic lactones, produced macrocyclic lactams or ketones, respectively. The simple approach can be readily applied to the preparation of a variety of macrocyclic lactones, lactams, and ketones with tunable ring sizes.

  7. 4-Hydroxy-7-oxo-5-heptenoic Acid Lactone Induces Angiogenesis through Several Different Molecular Pathways.

    PubMed

    Guo, Junhong; Linetsky, Mikhail; Yu, Annabelle O; Zhang, Liang; Howell, Scott J; Folkwein, Heather J; Wang, Hua; Salomon, Robert G

    2016-12-19

    Oxidative stress and angiogenesis have been implicated not only in normal phenomena such as tissue healing and remodeling but also in many pathological processes. However, the relationships between oxidative stress and angiogenesis still remain unclear, although oxidative stress has been convincingly demonstrated to influence the progression of angiogenesis under physiological and pathological conditions. The retina is particularly susceptible to oxidative stress because of its intensive oxygenation and high abundance of polyunsaturated fatty acyls. In particular, it has high levels of docosahexanoates, whose oxidative fragmentation produces 4-hydroxy-7-oxo-5-heptenoic acid lactone (HOHA-lactone). Previously, we found that HOHA-lactone is a major precursor of 2-(ω-carboxyethyl)pyrrole (CEP) derivatives, which are tightly linked to age-related macular degeneration (AMD). CEPs promote the pathological angiogenesis of late-stage AMD. We now report additional mechanisms by which HOHA-lactone promotes angiogenesis. Using cultured ARPE-19 cells, we observed that HOHA-lactone induces secretion of vascular endothelial growth factor (VEGF), which is correlated to increases in reactive oxygen species and decreases in intracellular glutathione (GSH). Wound healing and tube formation assays provided, for the first time, in vitro evidence that HOHA-lactone induces the release of VEGF from ARPE-19 cells, which promotes angiogenesis by human umbilical vein endothelial cells (HUVEC) in culture. Thus, HOHA-lactone can stimulate vascular growth through a VEGF-dependent pathway. In addition, results from MTT and wound healing assays as well as tube formation experiments showed that GSH-conjugated metabolites of HOHA-lactone stimulate HUVEC proliferation and promote angiogenesis in vitro. Previous studies demonstrated that HOHA-lactone, through its CEP derivatives, promotes angiogenesis in a novel Toll-like receptor 2-dependent manner that is independent of the VEGF receptor or VEGF

  8. The thermodynamic properties of alkylated γ-lactones

    NASA Astrophysics Data System (ADS)

    Emel'Yanenko, V. N.; Verevkin, S. P.; Burakova, E. N.; Roganov, G. N.; Georgieva, M. K.

    2009-04-01

    The enthalpies of formation of γ-pentanolactone ( I), γ-hexanolactone ( II), and γ-nonanolactone ( III) were determined by combustion calorimetry. The enthalpies of vaporization of these lactones were measured by the transfer method. Conformational analysis was performed and equilibrium structures, sets of fundamental vibrations, moments of inertia, and total energies of the stablest conformers of I, II, and III were calculated by the B3LYP/6-311G( d, p), G3MP2, and CBS-QB3 methods. The experimental IR spectra and calculated vibrational frequencies were used to obtain sets of fundamental vibrations of the stablest conformations. The thermodynamic properties of I- III in the ideal gas state were determined over the temperature range 0-1500 K. Additive and quantum-chemical methods were applied to estimate the Δf H o(g) values of a number of γ-lactones. Composite quantum-chemical methods were used to obtain the energies of monomethyl γ-butyrolactones and estimate their relative stability depending on the position of the methyl substituent in the ring.

  9. Copolymerization of carbon dioxide and butadiene via a lactone intermediate.

    PubMed

    Nakano, Ryo; Ito, Shingo; Nozaki, Kyoko

    2014-04-01

    Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide.

  10. Copolymerization of carbon dioxide and butadiene via a lactone intermediate

    NASA Astrophysics Data System (ADS)

    Nakano, Ryo; Ito, Shingo; Nozaki, Kyoko

    2014-04-01

    Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its use as a monomer in copolymerization with olefins has long been an elusive endeavour. A major obstacle for this process is that the propagation step involving carbon dioxide is endothermic; typically, attempted reactions between carbon dioxide and an olefin preferentially yield olefin homopolymerization. Here we report a strategy to circumvent the thermodynamic and kinetic barriers for copolymerizations of carbon dioxide and olefins by using a metastable lactone intermediate, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one, which is formed by the palladium-catalysed condensation of carbon dioxide and 1,3-butadiene. Subsequent free-radical polymerization of the lactone intermediate afforded polymers of high molecular weight with a carbon dioxide content of 33 mol% (29 wt%). Furthermore, the protocol was applied successfully to a one-pot copolymerization of carbon dioxide and 1,3-butadiene, and one-pot terpolymerizations of carbon dioxide, butadiene and another 1,3-diene. This copolymerization technique provides access to a new class of polymeric materials made from carbon dioxide.

  11. Cytotoxic sesquiterpene lactones from the root of Saussurea lappa.

    PubMed

    Sun, Chang-Ming; Syu, Wan-Jr; Don, Ming-Jaw; Lu, Jang-Jih; Lee, Gum-Hee

    2003-09-01

    Bioassay-directed fractionation of Saussurea lappa led to the isolation of a novel lappadilactone (1) and seven sesquiterpene lactones (2-8) as cytotoxic principles against selected human cancer cell lines. Lappadilactone (1), dehydrocostuslactone (2), and costunolide (5) exhibited the most potent cytotoxicity with CD50 values in the range 1.6-3.5 microg/mL in dose- and time-dependent manners. The cytotoxicities were not specific and showed similar activities against HepG2, OVCAR-3 and HeLa cell lines. The structure-activity relationship showed that the alpha-methylene-gamma-lactone moiety is necessary for cytotoxicity, and activity is reduced with the presence of a hydroxyl group. In addition, seven noncytotoxic compounds (9-15) were also isolated, including two novel sesquiterpenes, a guaianolide-type with a C17 skeleton, lappalone (13), and 1beta,6alpha-dihydroxycostic acid ethyl ester (14). The structures of the new compounds were elucidated from spectroscopic and/or X-ray data interpretations. Some representative compounds were also tested for antibacterial activity; however, only marginal activities were observed. Therefore, compounds 1-8 are potential cytotoxic agents but without significant antibacterial effect.

  12. Hologram QSAR studies of antiprotozoal activities of sesquiterpene lactones.

    PubMed

    Trossini, Gustavo H G; Maltarollo, Vinícius G; Schmidt, Thomas J

    2014-07-18

    Infectious diseases such as trypanosomiasis and leishmaniasis are considered neglected tropical diseases due the lack for many years of research and development into new drug treatments besides the high incidence of mortality and the lack of current safe and effective drug therapies. Natural products such as sesquiterpene lactones have shown activity against T. brucei and L. donovani, the parasites responsible for these neglected diseases. To evaluate structure activity relationships, HQSAR models were constructed to relate a series of 40 sesquiterpene lactones (STLs) with activity against T. brucei, T. cruzi, L. donovani and P. falciparum and also with their cytotoxicity. All constructed models showed good internal (leave-one-out q2 values ranging from 0.637 to 0.775) and external validation coefficients (r2test values ranging from 0.653 to 0.944). From HQSAR contribution maps, several differences between the most and least potent compounds were found. The fragment contribution of PLS-generated models confirmed the results of previous QSAR studies that the presence of α,β-unsatured carbonyl groups is fundamental to biological activity. QSAR models for the activity of these compounds against T. cruzi, L. donovani and P. falciparum are reported here for the first time. The constructed HQSAR models are suitable to predict the activity of untested STLs.

  13. Potent Cytotoxic Arylnaphthalene Lignan Lactones from Phyllanthus poilanei

    PubMed Central

    2015-01-01

    Two new (1 and 2) and four known arylnaphthalene lignan lactones (3–6) were isolated from different plant parts of Phyllanthus poilanei collected in Vietnam, with two further known analogues (7 and 8) being prepared from phyllanthusmin C (4). The structures of the new compounds were determined by interpretation of their spectroscopic data and by chemical methods, and the structure of phyllanthusmin D (1) was confirmed by single-crystal X-ray diffraction analysis. Several of these arylnaphthalene lignan lactones were cytotoxic toward HT-29 human colon cancer cells, with compounds 1 and 7-O-[(2,3,4-tri-O-acetyl)-α-l-arabinopyranosyl)]diphyllin (7) found to be the most potent, exhibiting IC50 values of 170 and 110 nM, respectively. Compound 1 showed activity when tested in an in vivo hollow fiber assay using HT-29 cells implanted in immunodeficient NCr nu/nu mice. Mechanistic studies showed that this compound mediated its cytotoxic effects by inducing tumor cell apoptosis through activation of caspase-3, but it did not inhibit DNA topoisomerase IIα activity. PMID:24937209

  14. N-3-Oxo-Decanoyl-l-Homoserine-Lactone Activates Auxin-Induced Adventitious Root Formation via Hydrogen Peroxide- and Nitric Oxide-Dependent Cyclic GMP Signaling in Mung Bean1[C][W][OA

    PubMed Central

    Bai, Xuegui; Todd, Christopher D.; Desikan, Radhika; Yang, Yongping; Hu, Xiangyang

    2012-01-01

    N-Acyl-homoserine-lactones (AHLs) are bacterial quorum-sensing signaling molecules that regulate population density. Recent evidence demonstrates their roles in plant defense responses and root development. Hydrogen peroxide (H2O2), nitric oxide (NO), and cyclic GMP (cGMP) are essential messengers that participate in various plant physiological processes, but how these messengers modulate the plant response to N-acyl-homoserine-lactone signals remains poorly understood. Here, we show that the N-3-oxo-decanoyl-homoserine-lactone (3-O-C10-HL), in contrast to its analog with an unsubstituted branch chain at the C3 position, efficiently stimulated the formation of adventitious roots and the expression of auxin-response genes in explants of mung bean (Vigna radiata) seedlings. This response was mimicked by the exogenous application of auxin, H2O2, NO, or cGMP homologs but suppressed by treatment with scavengers or inhibitors of H2O2, NO, or cGMP metabolism. The 3-O-C10-HL treatment enhanced auxin basipetal transport; this effect could be reversed by treatment with H2O2 or NO scavengers but not by inhibitors of cGMP synthesis. Inhibiting 3-O-C10-HL-induced H2O2 or NO accumulation impaired auxin- or 3-O-C10-HL-induced cGMP synthesis; however, blocking cGMP synthesis did not affect auxin- or 3-O-C10-HL-induced H2O2 or NO generation. Additionally, cGMP partially rescued the inhibitory effect of H2O2 or NO scavengers on 3-O-C10-HL-induced adventitious root development and auxin-response gene expression. These results suggest that 3-O-C10-HL, unlike its analog with an unmodified branch chain at the C3 position, can accelerate auxin-dependent adventitious root formation, possibly via H2O2- and NO-dependent cGMP signaling in mung bean seedlings. PMID:22138973

  15. Membrane anchoring of diacylglycerol lactones substituted with rigid hydrophobic acyl domains correlates with biological activities.

    PubMed

    Raifman, Or; Kolusheva, Sofiya; Comin, Maria J; Kedei, Noemi; Lewin, Nancy E; Blumberg, Peter M; Marquez, Victor E; Jelinek, Raz

    2010-01-01

    Synthetic diacylglycerol lactones (DAG lactones) are effective modulators of critical cellular signaling pathways downstream of the lipophilic second messenger diacylglycerol that activate a host of protein kinase C (PKC) isozymes as well as other non-kinase proteins that share with PKC similar C1 membrane-targeting domains. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study characterizes the membrane interactions and bilayer anchoring of a series of DAG lactones in which the hydrophobic moiety is a 'molecular rod', namely a rigid 4-[2-(R-phenyl)ethynyl]benzoate moiety in the acyl position. Use of assays employing chromatic biomimetic vesicles and biophysical techniques revealed that the mode of membrane anchoring of the DAG lactone derivatives was markedly affected by the presence of the hydrophobic diphenyl rod and by the size of the functional unit at the terminus of the rod. Two primary mechanisms of interaction were observed: surface binding of the DAG lactones at the lipid/water interface and deep insertion of the ligands into the alkyl core of the lipid bilayer. These membrane-insertion properties could explain the different patterns of the PKC translocation from the cytosol to membranes that is induced by the molecular-rod DAG lactones. This investigation emphasizes that the side residues of DAG lactones, rather than simply conferring hydrophobicity, profoundly influence membrane interactions, and thus may further contribute to the diversity of biological actions of these synthetic biomimetic ligands.

  16. Towards the industrialization of new biosurfactants: Biotechnological opportunities for the lactone esterase gene from Starmerella bombicola.

    PubMed

    Roelants, Sophie L K W; Ciesielska, Katarzyna; De Maeseneire, Sofie L; Moens, Helena; Everaert, Bernd; Verweire, Stijn; Denon, Quenten; Vanlerberghe, Brecht; Van Bogaert, Inge N A; Van der Meeren, Paul; Devreese, Bart; Soetaert, Wim

    2016-03-01

    Although sophorolipids (SLs) produced by S. bombicola are a real showcase for the industrialization of microbial biosurfactants, some important drawbacks are associated with this efficient biological process, e.g., the simultaneous production of acidic and lactonic SLs. Depending on the application, there is a requirement for the naturally produced mixture to be manipulated to give defined ratios of the components. Recently, the enzyme responsible for the lactonization of SLs was discovered. The discovery of the gene encoding this lactone esterase (sble) enabled the development of promising S. bombicola strains producing either solely lactonic (using a sble overexpression strain described in this paper: oe sble) or solely acidic SLs (using a sble deletion strain, which was recently described, but not characterized yet: Δsble). The new S. bombicola strains were used to investigate the production processes (fermentation and purification) of either lactonic or acidic SLs. The strains maintain the high inherent productivities of the wild-type or even perform slightly better and thus represent a realistic industrial opportunity. 100% acidic SLs with a mixed acetylation pattern were obtained for the Δsble strain, while the inherent capacity to selectively produce lactonic SLs was significantly increased (+42%) for the oe sble strain (99% lactonic SLs). Moreover, the regulatory effect of citrate on lactone SL formation for the wild-type was absent in this new strain, which indicates that it is more robust and better suited for the industrial production of lactonic SLs. Basic parameters were determined for the purified SLs, which confirm that the two new strains produce molecules with distinctive properties of which the application potential can now easily be investigated independently.

  17. Conformationally Constrained Analogues of Diacylglycerol (DAG). 31. Modulation of the Biological Properties of Diacylgycerol Lactones (DAG-lactones) Containing Rigid-Rod Acyl Groups Separated from the Core Lactone by Spacer Units of Different Lengths

    PubMed Central

    2009-01-01

    Diacylglycerol lactones built with a rigid 4-[(methylphenyl)ethynyl]phenyl rod that is separated from the exocyclic acylcarbonyl of the DAG-lactone core by a spacer unit of variable length were synthesized and studied. Binding affinities for a panel of classical and novel PKC isozymes in two different phospholipid environments, one corresponding to the plasma membrane of cells, were determined. The kinetics and site of translocation for the PKC isozymes α and δ upon treatment with the compounds were also studied as well as the early response of ERK phosphorylation and the late response of induction of apoptosis in the human prostatic carcinoma cell line LNCaP. Finally, the compounds were evaluated in terms of their interaction with biomimetic lipid/polydiacetylene membranes by the associated chromatic response. The different spatial disposition of the rigid structural motif on the DAG-lactones contributes to differential activity. PMID:19379015

  18. Synthesis, characterization and antiproliferative activity of β-aryl-δ-iodo-γ-lactones

    NASA Astrophysics Data System (ADS)

    Wzorek, Alicja; Gawdzik, Barbara; Gładkowski, Witold; Urbaniak, Mariusz; Barańska, Anita; Malińska, Maura; Woźniak, Krzysztof; Kempińska, Katarzyna; Wietrzyk, Joanna

    2013-09-01

    A convenient pathway for the synthesis of new of β-aryl-δ-iodo-γ-lactones is described. The synthetic route led to both cis and trans isomers which were separated by column chromatography or crystallization. The structures of synthesized compounds were confirmed by spectroscopic methods: IR, NMR and HR-MS. For lactones with naphthyl ring (6e and 7e) the crystal structures were also obtained. The lactones were screened for biological evaluation against cancer line HL-60 (human promyelocytic leukemia). The tests showed that the presence of substituent at the benzene ring does not significantly affect the antiproliferative activity of the compound.

  19. Remodeling Natural Products: Chemistry and Serine Hydrolase Activity of a Rocaglate-Derived β-Lactone

    PubMed Central

    2015-01-01

    Flavaglines are a class of natural products with potent insecticidal and anticancer activities. β-Lactones are a privileged structural motif found in both therapeutic agents and chemical probes. Herein, we report the synthesis, unexpected light-driven di-epimerization, and activity-based protein profiling of a novel rocaglate-derived β-lactone. In addition to in vitro inhibition of the serine hydrolases ABHD10 and ACOT1/2, the most potent β-lactone enantiomer was also found to inhibit these enzymes, as well as the serine peptidases CTSA and SCPEP1, in PC3 cells. PMID:24447064

  20. 180 degree unidirectional bond rotation in a biaryl lactone artificial molecular motor prototype.

    PubMed

    Dahl, Bart J; Branchaud, Bruce P

    2006-12-07

    A bifunctional biaryl lactone has been synthesized that should be capable of iterative unidirectional aryl-aryl bond rotation via: (1) a diastereoselective lactone ring opening, (S)-1 to (P,S)-2 or (M,S)-2; (2) a chemoselective lactonization, (P,S)-2 or (M,S)-2 to (S)-3; and (3) a chemoselective hydrolysis, (S)-3 to (S)-1. Preliminary results of a racemic sample have indicated unidirectional 180 degrees rotation with very high directional selectivity per individual artificial molecular motor molecule through the first two steps of this sequence. [reaction: see text

  1. How do the macrocyclic lactones kill filarial nematode larvae?

    PubMed Central

    Wolstenholme, Adrian J.; Maclean, Mary J.; Coates, Ruby; McCoy, Ciaran J.; Reaves, Barbara J.

    2017-01-01

    The macrocyclic lactones (MLs) are one of the few classes of drug used in the control of the human filarial infections, onchocerciasis and lymphatic filariasis, and the only one used to prevent heartworm disease in dogs and cats. Despite their importance in preventing filarial diseases, the way in which the MLs work against these parasites is unclear. In vitro measurements of nematode motility have revealed a large discrepancy between the maximum plasma concentrations achieved after drug administration and the amounts required to paralyze worms. Recent evidence has shed new light on the likely functions of the ML target, glutamate-gated chloride channels, in filarial nematodes and supports the hypothesis that the rapid clearance of microfilariae that follows treatment involves the host immune system. PMID:27279086

  2. Five new lactone derivatives from the stems of Dendrobium nobile.

    PubMed

    Zhou, Xue-Ming; Zheng, Cai-Juan; Wu, Jia-Ting; Chen, Guang-Ying; Chen, Jun; Sun, Chong-Ge

    2016-12-01

    Five new lactone derivatives decumbic acids A and B (1 and 2), (-)-decumbic acid (3a), (-)- and (+)-dendrolactone (4a and 4b) together with four known compounds (3b and 5-7) were isolated from the stems of Dendrobium nobile. Their structures were elucidated using comprehensive spectroscopic methods. Compounds 3a and 3b, 4a and 4b were isolated as two pair of enantiomers by chiral HPLC. The absolute configurations of 1, 2, 3a, 4a and 4b were determined by optical rotation and X-ray crystallographic analysis. The inhibitory activities of all compounds against nine phytopathogenic fungi and three cancer cell lines were evaluated. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. How do the macrocyclic lactones kill filarial nematode larvae?

    PubMed

    Wolstenholme, Adrian J; Maclean, Mary J; Coates, Ruby; McCoy, Ciaran J; Reaves, Barbara J

    2016-09-01

    The macrocyclic lactones (MLs) are one of the few classes of drug used in the control of the human filarial infections, onchocerciasis and lymphatic filariasis, and the only one used to prevent heartworm disease in dogs and cats. Despite their importance in preventing filarial diseases, the way in which the MLs work against these parasites is unclear. In vitro measurements of nematode motility have revealed a large discrepancy between the maximum plasma concentrations achieved after drug administration and the amounts required to paralyze worms. Recent evidence has shed new light on the likely functions of the ML target, glutamate-gated chloride channels, in filarial nematodes and supports the hypothesis that the rapid clearance of microfilariae that follows treatment involves the host immune system.

  4. Polypropionate lactones of deoxysugars glycosides from slime mold Lycogala epidendrum.

    PubMed

    Rezanka, Tomás; Dvoráková, Radmila

    2003-08-01

    Two novel polypropionate lactone glycosides (1 and 2, i.e. lycogalinosides A and B) were isolated from the slime mold Lycogala epidendrum. Their structures, including the absolute configurations of the hydroxyl and methyls groups, were determined by means of extensive spectroscopic data such as mass, IR, UV, and 1D and 2D NMR spectra and chemical degradation followed by spectroscopic and chromatographic analysis. Compounds 1 and 2 are unique in structure containing a 2-deoxy-alpha-L-fucopyranosyl-(1-4)-6-deoxy-beta-D-gulopyranosyl unit and a beta-D-olivopyranosyl-(1-4)-beta-D-fucopyranosyl unit, respectively, and showed growth inhibitory activities against Gram-positive bacteria.

  5. Oxyuris equi: lack of efficacy in treatment with macrocyclic lactones.

    PubMed

    Wolf, Denis; Hermosilla, Carlos; Taubert, Anja

    2014-03-17

    Whilst anthelminthic resistance of small strongyles is well documented, anthelmintic failures against infections with Oxyuris equi have scarcely been published so far. We describe two cases of equine oxyurosis and the anthelminthic failure of macrocyclic lactones (moxidectin, ivermectin) resulting in persistent O. equi infections with continuous egg shedding. The horses were kept in two different herds in the federal state of Hessia, Germany. Herd A kept two geldings: an 8-year-old Welsh-Cob-Mix and a 7-year-old Haflinger. Herd B was composed of four animals: 2 Connemara-mares, 31 and 19 years old, one 18-year-old Connemara-gelding and a 27-year-old Norwegian Fjord mare. All animals had a case history of various anthelmintic treatments with macrocyclic lactones (moxidectin and ivermectin alternating irregulary) in 2010 and 2011, nonetheless, they continued to shed O. equi nematodes and eggs. Animals were treated anew with moxidectin by members of the institute and were continuously monitored on a daily base by adhesive tape samples. Follow-up examinations for the reappearance of eggs were performed for 30 days in Herd A and 57 days in Herd B. In total, recurrence of O. equi egg shedding was detected in three out of six horses within 1-4 weeks after treatment. In both herds accompanying horses sharing the same stable and paddock remained negative for detection of O. equi-eggs or worms throughout the whole observation period. This is the first report in Europe showing inefficacy of commercial ivermectin compounds and furthermore the first report at all documenting ineffectiveness of moxidectin compounds in the treatment of O. equi-infections in horses indicating a possible development of resistance or confirming an existing incomplete oxyuricidal efficacy. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Sesquiterpene Lactone Composition of Wild and Cultivated Sunflowers and Biological Activity against an Insect Pest.

    PubMed

    Prasifka, Jarrad R; Spring, Otmar; Conrad, Jürgen; Cook, Leonard W; Palmquist, Debra E; Foley, Michael E

    2015-04-29

    Sesquiterpene lactones in sunflowers, Helianthus spp., are important to interactions with pathogens, weeds, and insects. Across a broad range of Helianthus annuus, differences in composition of sesquiterpene lactones extracted from disc florets were found between wild and cultivated sunflowers and also between distinct groups of inbreds used to produce sunflower hybrids. Discriminant function analysis showed the presence and relative abundance of argophyllone B, niveusin B, and 15-hydroxy-3-dehydrodesoxyfruticin were usually (75%) effective at classifying wild sunflowers, cultivated inbreds, and hybrids. Argophyllone B reduced the larval mass of the sunflower moth, Homeosoma electellum, by >30%, but only at a dose greater than that found in florets. Low doses of mixed extracts from cultivated florets produced a similar (≈40%) reduction in larval mass, suggesting combinations of sesquiterpene lactones act additively. Although the results support a role for sesquiterpene lactones in herbivore defense of cultivated sunflowers, additional information is needed to use these compounds purposefully in breeding.

  7. Variecolactol: A New Sesterterpene Lactone from the Sclerotia of Aspergillus auricomus (Guegen) Saito

    USDA-ARS?s Scientific Manuscript database

    Variecolactol (1), a new sesterterpene lactone related to variecolin (2), has been isolated from the organic extracts of Aspergillus auricomus. Structure determination of this compound was achieved primarily through HMQC, HMBC, and NOESY experiments. The known compounds dihydropenicillic acid (3) ...

  8. Dehydrocostus lactone prevents mitochondrial dysfunction in osteoblastic MC3T3-E1 cells.

    PubMed

    Choi, Eun Mi

    2011-08-16

    The dried root of Saussurea lappa Clarke (Compositae) has been used as a traditional medicine. Dehydrocostus lactone is one of the main bioactive constituents of this medicinal plant. In the present study, the protective effect of dehydrocostus lactone against antimycin A (an inhibitor of mitochondrial complex III)-induced cytotoxicity was investigated in osteoblastic MC3T3-E1 cells. Pre-treatment with dehydrocostus lactone prior to antimycin A exposure significantly prevented mitochondrial membrane potential dissipation, complex IV inactivation, ATP loss, cytochrome c release, intracellular calcium elevation and potassium loss, and reactive oxygen species production induced by antimycin A. These results suggest that dehydrocostus lactone protects osteoblastic MC3T3-E1 cells from antimycin A-induced cell damage through the improved mitochondrial function.

  9. Synthesis and biological evaluation of α,β-unsaturated lactones as potent immunosuppressive agents.

    PubMed

    Lee, Sun-Mi; Lee, Won-Gil; Kim, Young-Chul; Kim, Yong-Chul; Ko, Hyojin

    2011-10-01

    Compounds having α,β-unsaturated lactones display a variety of biological activities. Many research groups have tested both natural and unnatural α,β-unsaturated lactones for as-yet undiscovered biological properties. We synthesized α,β-unsaturated lactones with various substituents at the δ-position and studied their immunosuppressive effects, that is, the inhibition of Interleukin-2 (IL-2) production. Among the compounds synthesized, the benzofuran-substituted α,β-unsaturated lactone 4h showed the best inhibitory activity toward IL-2 production in Jurkat e6-1 T lymphocytes (IC(50)=66.9 nM) without cytotoxicity at 10 μM. The results indicated that 4h may be useful as a potent immunosuppressive agent, as well as in IL-2-related studies. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. β-Lactone formation during product release from a nonribosomal peptide synthetase.

    PubMed

    Schaffer, Jason E; Reck, Margaret R; Prasad, Neha K; Wencewicz, Timothy A

    2017-07-01

    Nonribosomal peptide synthetases (NRPSs) are multidomain modular biosynthetic assembly lines that polymerize amino acids into a myriad of biologically active nonribosomal peptides (NRPs). NRPS thioesterase (TE) domains employ diverse release strategies for off-loading thioester-tethered polymeric peptides from termination modules typically via hydrolysis, aminolysis, or cyclization to provide mature antibiotics as carboxylic acids/esters, amides, and lactams/lactones, respectively. Here we report the enzyme-catalyzed formation of a highly strained β-lactone ring during TE-mediated cyclization of a β-hydroxythioester to release the antibiotic obafluorin (Obi) from an NRPS assembly line. The Obi NRPS (ObiF) contains a type I TE domain with a rare catalytic cysteine residue that plays a direct role in β-lactone ring formation. We present a detailed genetic and biochemical characterization of the entire Obi biosynthetic gene cluster in plant-associated Pseudomonas fluorescens ATCC 39502 that establishes a general strategy for β-lactone biogenesis.

  11. [Kinetics of the lactone-carboxylate transition of hybrid camptothecin-netropsin molecules].

    PubMed

    Oleĭnikov, V A; Ustinova, O A; Mochalov, K E; Ermishov, M A; Grokhovskiĭ, S L; Zhuze, A L; Sukhanova, A V; Nabiev, I R

    2003-01-01

    The kinetics of the hydrolysis of the lactone ring of a hybrid molecule containing the molecules of the antitumor drug camptothecin and a derivative of the antibiotic netropsines, which is highly affine and specific to the DNA A-T sequences was investigated. It was shown that intramolecular interaction significantly slows down the rate of hydrolysis but does not change the equilibrium ratio of concentrations of the lactone and carboxylate forms of the camptothecin fragment of the hybrid molecule, which corresponds to the pH value. The use of intramolecular interaction for controlling the kinetics of the lactone/carboxylate transition makes it possible to create the drugs of the camptothecin family, which preserve the biologically active lactone form under the physiological conditions for a longer time and, therefore, are more effective as anticancer agents.

  12. Sesquiterpene lactones derived from Saussurea lappa induce apoptosis and inhibit invasion and migration in neuroblastoma cells.

    PubMed

    Tabata, Keiichi; Nishimura, Yuki; Takeda, Taiji; Kurita, Masahiro; Uchiyama, Taketo; Suzuki, Takashi

    2015-04-01

    Neuroblastoma is among the most fatal of solid tumors in the pediatric age group, even when treated aggressively. Therefore, a new effective therapeutic drug(s) for neuroblastoma is urgently needed. To clarify the anticancer effects of the sesquiterpene lactones dehydrocostus lactone and costunolide, derived from Saussurea lappa, we examined the cytotoxic and migration/invasion-inhibitory effects of these compounds against neuroblastoma cell lines. Both the compounds exerted significant cytotoxicity against the neuroblastoma cell lines IMR-32, NB-39, SK-N-SH, and LA-N-1. Evidence of cellular apoptosis, such as nuclear condensation and membrane inversion, were observed after treatment with these compounds. Both compounds induced caspase-7 activation and PARP cleavage as confirmed by Western blotting. Furthermore, the sesquiterpene lactones also suppressed invasion and migration of the neuroblastoma cells. These results suggest that dehydrocostus lactone and costunolide are promising candidates for being developed into novel anticancer drugs effective against neuroblastoma.

  13. Statin induced myotoxicity: the lactone forms are more potent than the acid forms in human skeletal muscle cells in vitro.

    PubMed

    Skottheim, Ine Blankenberg; Gedde-Dahl, Ane; Hejazifar, Solmaz; Hoel, Kjersti; Asberg, Anders

    2008-04-23

    Statins exist in both acid and lactone forms in vivo. High plasma levels of the lactone forms have been observed in patients with statin induced myopathy. In the present study, the hypothesis that lactone forms have a higher potency of inducing myotoxicity as compared to acid forms was investigated. Primary human skeletal muscle cells were incubated with increasing concentrations of lactone and acid forms of atorvastatin, fluvastatin, pravastatin and simvastatin. Following incubation, living myotubes were quantified by fluorescence staining. Atorvastatin lactone showed a 14-fold, fluvastatin lactone a 26-fold, pravastatin lactone a 23-fold, and simvastatin lactone a 37-fold higher potency to induce myotoxicity compared to their corresponding acid forms. Thus, for the four different statins the present study shows a significantly higher potency of the lactone forms, than the respective acid forms, to induce myotoxicity in human skeletal muscle cells in vitro. These results clearly indicate the need to differentiate between acid and lactone forms in future investigation of statin myotoxicity.

  14. Xanthates as synthetic equivalents of oxyacyl radicals: access to lactones under tin-free conditions.

    PubMed

    Davy, Jason A; Mason, Jeremy W; Moreau, Benoît; Wulff, Jeremy E

    2012-07-20

    In addition to their utility in Barton-McCombie deoxygenations, xanthates can engage in 5-exo-trig radical cyclizations to afford lactones after oxidative workup. In this paper, we describe a tin-free protocol that provides direct access to lactones via hydrolysis of labile thioketal intermediates. Analysis of several systems of varying complexity reveals that the reaction is most applicable for constrained systems in which the reacting center is prepositioned near the radical-accepting alkene.

  15. Enantiodifferentiation of whisky and cognac lactones using gas chromatography with different cyclodextrin chiral stationary phases.

    PubMed

    Schmarr, Hans-Georg; Mathes, Maximilian; Wall, Kristina; Metzner, Frank; Fraefel, Marius

    2017-09-22

    The chiral lactone 5-butyl-4-methyloxolan-2-one or 5-butyl-4-methyldihydro-2(3H)-furanone, often named whisky lactone, is found in oak wood, then contributing to the appreciated flavor of beverages stored in such wooden barrels. Its next higher homologue is named cognac lactone (5-pentyl-4-methyloxolan-2-one or 5-pentyl-4-methyldihydro-2(3H)-furanone), however is much less known, probably due to its minor concentration level. In order to study the direct enantioseparation of both lactones by gas chromatography on chiral stationary phases, individual enantiomers, particularly for cognac lactone were made available. This was achieved by baker's yeast reduction of synthesized ethyl 3-methyl-4-oxononanoate or, after hydrolysis, of the corresponding 4-ketoacid, that gave access to individual enantiomers of cognac lactone. Good enantioseparation was achieved for both whisky and cognac lactone with high values for the chiral resolution with 6-O-tert. butyl dimethylsilyl-2,3-dialkylated or 6-O-tert. butyl dimethylsilyl-2,3-diacylated cyclodextrin derivatives as chiral selectors. The influence of the nature and position of derivatization of the cyclodextrin moiety revealed a strong impact on the chiral recognition mechanism, as the investigated alkylated derivatives heptakis-(2,6-di-O-iso-pentyl-3-O-allyl)-β-cyclodextrin and octakis-(2,3-di-O-pentyl-6-O-methyl)-γ-cyclodextrin did not provide any or only minor chiral selectivity for the two lactones. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Lactone pathway to statins utilizing the Wittig reaction. The synthesis of rosuvastatin.

    PubMed

    Casar, Zdenko; Steinbücher, Miha; Kosmrlj, Janez

    2010-10-01

    The first entry to statins via lactonized side chain is reported, exemplified by the synthesis of rosuvastatin. The key step is Wittig coupling of (2S,4R)-4-(tert-butyldimethylsilyloxy)-6-oxotetrahydro-2H-pyran-2-carbaldehyde and phosphonium salt of an appropriately functionalized pyrimidine heterocycle. One-pot deprotection and hydrolysis of the resulting 4-O-TBS rosuvastatin lactone provided rosuvastatin in high yield.

  17. Sesquiterpene lactone stereochemistry influences herbivore resistance and plant fitness in the field

    PubMed Central

    Ahern, Jeffrey R.; Whitney, Kenneth D.

    2014-01-01

    Background and Aims Stereochemical variation is widely known to influence the bioactivity of compounds in the context of pharmacology and pesticide science, but our understanding of its importance in mediating plant–herbivore interactions is limited, particularly in field settings. Similarly, sesquiterpene lactones are a broadly distributed class of putative defensive compounds, but little is known about their activities in the field. Methods Natural variation in sesquiterpene lactones of the common cocklebur, Xanthium strumarium (Asteraceae), was used in conjunction with a series of common garden experiments to examine relationships between stereochemical variation, herbivore damage and plant fitness. Key Results The stereochemistry of sesquiterpene lactone ring junctions helped to explain variation in plant herbivore resistance. Plants producing cis-fused sesquiterpene lactones experienced significantly higher damage than plants producing trans-fused sesquiterpene lactones. Experiments manipulating herbivore damage above and below ambient levels found that herbivore damage was negatively correlated with plant fitness. This pattern translated into significant fitness differences between chemotypes under ambient levels of herbivore attack, but not when attack was experimentally reduced via pesticide. Conclusions To our knowledge, this work represents only the second study to examine sesquiterpene lactones as defensive compounds in the field, the first to document herbivore-mediated natural selection on sesquiterpene lactone variation and the first to investigate the ecological significance of the stereochemistry of the lactone ring junction. The results indicate that subtle differences in stereochemistry may be a major determinant of the protective role of secondary metabolites and thus of plant fitness. As stereochemical variation is widespread in many groups of secondary metabolites, these findings suggest the possibility of dynamic evolutionary histories

  18. Influence of cultivation site on sesquiterpene lactone composition of forage chicory (Cichorium intybus L.).

    PubMed

    Foster, Joyce G; Clapham, William M; Belesky, David P; Labreveux, Maria; Hall, Marvin H; Sanderson, Matt A

    2006-03-08

    The forage potential of chicory (Cichorium intybus L.) has not been realized in southern West Virginia (WV) because ruminants are reluctant to consume the herbage. Chicory contains bitter sesquiterpene lactones that can adversely impact palatability. This study was undertaken to determine whether sesquiterpene lactone concentrations in chicory grown in southern WV differ from those in chicory grown in central Pennsylvania (PA) where chicory is grazed readily. Herbage was collected in 1997 and 1998 from cultivars Grasslands Puna (Puna), INIA le Lacerta (Lacerta), and Forage Feast established at research sites near State College, PA, and Beckley, WV. The total concentration of sesquiterpene lactones in WV-grown cultivars was 0.58% (dry matter basis) in Puna, 0.59% in Lacerta, and 0.79% in Forage Feast in 1997 and ranged from 1.03 (Lacerta) to 1.52% (Forage Feast) in 1998. In PA-grown cultivars, sesquiterpene lactones represented 0.16 (Puna), 0.18 (Lacerta), and 0.27% (Forage Feast) of the forage dry matter in 1997 and ranged from 0.32 (Lacerta) to 0.55% (Forage Feast) in 1998. Concentrations of lactucin, lactucopicrin, and total sesquiterpene lactones in Forage Feast exceeded those in the other cultivars grown at the same site. The lowest concentrations of lactucopicrin and total sesquiterpene lactones observed among WV-grown cultivars were higher (2-fold or more) than the highest concentrations present in cultivars grown the same year in PA. Mineral analyses of soils from the two cultivation sites indicate that P availability may influence sesquiterpene lactone composition of chicory herbage. Results provide a foundation for future studies of environmental effects on sesquiterpene lactone composition and palatability of chicory herbage.

  19. Chirality of the gamma-lactones formed by Fusarium poae INRA 45.

    PubMed

    Latrasse, A; Guichard, E; Piffaut, C; Fournier, N; Dufosse, L

    1993-01-01

    A filamentous fungus, Fusarium poae INRA 45, was grown in two liquid Czapek-type media (a Czapek medium, and a yeast extract plus casaminoacids-enriched Czapek medium). Eight gamma-lactones, i.e., gamma-penta-, gamma-octa-, gamma-nona-, gamma-deca-, and gamma-dodecalactone, (6Z)-gamma- and (6E)-gamma-dodecenolactones, and a di-unsaturated gamma-dodecalactone, were tentatively, or conclusively, identified by capillary gas chromatography (GC) and coupled GC-MS, in the volatile fractions of the cultures. Kinetics of the formation of gamma-dodecalactone, (6Z)-gamma- and (6E)-gamma-dodecenolactones, (three major lactones), and gamma-dodecalactone (a minor lactone) were quantitatively studied by computerized GC integration. Variations of the (R/S) ratios of the lactone enantiomers were quantitatively studied by computerized multidimensional gas chromatography (MDGC) integration. The levels of the lactones were superior in the enriched Czapek-type medium to those of the Czapek medium, but the compositions of these media did not influence significantly the (R/S) ratios of these lactones. Formation of the enantiomers is discussed in terms of metabolism of potential precursors.

  20. Two new aliphatic lactones from the fruits of Coriandrum sativum L.

    PubMed Central

    2012-01-01

    Background The present paper describes the isolation and characterization of two new aliphatic δ-lactones along with three glycerides and n-nonadecanyl cetoleate from the fruits of Coriandrum sativum L. (Apiaceae). The structures of all the isolated phytoconstituents have been established on the basis of spectral data analysis and chemical reactions. Results Phytochemical investigation of the methanolic extract of C. sativum L. (Apiaceae) fruits resulted in the isolation of two new aliphatic δ-lactones characterized as 2α-n-heptatriacont-(Z)-3-en-1,5-olide (1) (coriander lactone) and 2α-n-tetracont-(Z,Z)-3,26-dien-18α-ol-1,5-olide (2) (hydroxy coriander lactone) together with glyceryl-1,2-dioctadec-9,12-dienoate-3-octadec-9-enoate (3); glyceryl-1,2,3-trioctadecanoate (4); n-nonadecanyl-n-docos-11-enoate (5) and oleiyl glucoside (6). Conclusions Phytochemical investigation of the methanolic extract of C. sativum gave coriander lactone and hydroxy coriander lactone as the new phytoconstituents. PMID:22800677

  1. Modified hydrolysis kinetics of the active lactone moiety of 10-hydroxycamptothecin by liposomal encapsulation.

    PubMed

    Shi, Kai; Tian, Ye; Jiang, Yanbo; Wang, Lan; Cui, Fude

    2010-12-01

    The key structural requirement for the antitumor activity of 10-hydroxycamptothecin (HCPT) is the intact lactone moiety which is always instability and suffered from pH-dependent hydrolysis. The aim of this study was to evaluate the protection effects of liposomal encapsulation on the labile lactone ring. Mono-modal dispersed quasi-spherical liposomes with mean diameter of 145 nm and high drug entrapment efficiency of 90% were obtained under optimal conditions. The in vitro hydrolysis kinetics behaviors of lactone were studied in varied pH buffers. Compared to that of free HCPT in solution formulation, both the hydrolysis half-life and observed equilibrium constant of liposomal HCPT were increased significantly along with the decreased apparent hydrolysis rate constant. The plasma pharmacokinetics was studied by assessing the lactone stability versus time profiles in vivo following intravenous administration of free and liposomal HCPT. The liposomal encapsulation led to a twofold increase in the AUC values and significant decrease in the plasma clearance of lactone (P < 0.05). There was a good correlation between in vitro and in vivo stability of HCPT-lactone. These results suggested a potential application of the novel liposome formulation for the stable delivery system of HCPT.

  2. Membrane-surface anchoring of charged diacylglycerol-lactones correlates with biological activities

    PubMed Central

    Raifman, Or; Kolusheva, Sofiya; Kazzouli, Said El; Sigano, Dina M.; Kedei, Noemi; Lewin, Nancy E.; Lopez-Nicolas, Ruben; Ortiz-Espin, Ana; Gomez-Fernandez, Juan C.; Blumberg, Peter M.; Marquez, Victor E.; Corbalan, Senena; Jelinek, Raz

    2013-01-01

    Synthetic diacylglycerol lactones (DAG-lactones) are effective modulators of critical cellular signaling pathways, downstream of the lipophilic second messenger diacylglycerol, that activate a host of protein kinase C (PKC) isozymes and other non-kinase proteins that share with PKC similar C1 membrane-targeting domains. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study examines the biological properties of charged DAG-lactones exhibiting different alkyl groups attached to the heterocyclic nitrogen of an α–pyridylalkylidene chain, and particularly the relationship between membrane interactions of the substituted DAG-lactones and their respective biological activities. Our results suggest that bilayer interface localization of the N-alkyl chain in the R2 position of the DAG-lactones inhibits translocation of PKC isoenzymes onto the cellular membrane. However, the orientation of a branched alkyl chain at the bilayer surface facilitates PKC binding and translocation. This investigation emphasizes that bilayer localization of the aromatic side residues of positively-charged DAG lactone derivatives play a central role in determining biological activity and that this factor contributes to the diversity of biological actions of these synthetic biomimetic ligands. PMID:20715268

  3. Germa-gamma-lactones as novel inhibitors of bacterial urease activity.

    PubMed

    Amtul, Zareen; Follmer, Cristian; Mahboob, Sumera; Atta-Ur-Rahman; Mazhar, Muhammad; Khan, Khalid M; Siddiqui, Rafat A; Muhammad, Sajjad; Kazmi, Syed A; Choudhary, Mohammad Iqbal

    2007-05-04

    Organogermanium compounds have been used as pharmacological agents. However, very few reports are available on the synthesis and antibacterial activities of lactones containing organogermaniums. The purpose of the present investigation was to determine the effects of different lactone-substituted organogermaniums on bacterial growth and their urease activity. We report synthesis of 12 germa-gamma-lactones (GeL) and their antimicrobial activities against several bacterial pathogens. Antibacterial action of all GeL was highly selective against Gram-negative bacilli, particularly Proteus mirabilis, an important pathogen infecting the urinary tract. Furthermore, our data indicate that 8-quinoline derivatives were more potent against P. mirabilis than 2-methyl-8-quinoline. For example, the beta-(o-methylphenyl)-gamma,gamma-bis(8-quinolinoxy)germa-gamma-lactone and beta-(o-methoxyphenyl)-gamma,gamma-bis(8-quinolinoxy)germa-gamma-lactone were maximally active with MIC(90) of 61 and 94 microM, respectively. In vitro studies demonstrated a linear correlation between antibacterial activity and inhibition of P. mirabilis urease enzyme. Further kinetic analyses revealed that inhibition occurred in a noncompetitive and concentration-dependent manner with the minimum IC(50) of 31 microM for beta-(o-methoxyphenyl)-gamma,gamma-bis(8-quinolinoxy)germa-gamma-lactone. In conclusion, these findings suggest that GeL have potential to be developed as antimicrobial agents against P. mirabilis infection.

  4. Biochar and microbial signaling: production conditions determine effects on microbial communication.

    PubMed

    Masiello, Caroline A; Chen, Ye; Gao, Xiaodong; Liu, Shirley; Cheng, Hsiao-Ying; Bennett, Matthew R; Rudgers, Jennifer A; Wagner, Daniel S; Zygourakis, Kyriacos; Silberg, Jonathan J

    2013-10-15

    Charcoal has a long soil residence time, which has resulted in its production and use as a carbon sequestration technique (biochar). A range of biological effects can be triggered by soil biochar that can positively and negatively influence carbon storage, such as changing the decomposition rate of organic matter and altering plant biomass production. Sorption of cellular signals has been hypothesized to underlie some of these effects, but it remains unknown whether the binding of biochemical signals occurs, and if so, on time scales relevant to microbial growth and communication. We examined biochar sorption of N-3-oxo-dodecanoyl-L-homoserine lactone, an acyl-homoserine lactone (AHL) intercellular signaling molecule used by many gram-negative soil microbes to regulate gene expression. We show that wood biochars disrupt communication within a growing multicellular system that is made up of sender cells that synthesize AHL and receiver cells that express green fluorescent protein in response to an AHL signal. However, biochar inhibition of AHL-mediated cell-cell communication varied, with the biochar prepared at 700 °C (surface area of 301 m(2)/g) inhibiting cellular communication 10-fold more than an equivalent mass of biochar prepared at 300 °C (surface area of 3 m(2)/g). These findings provide the first direct evidence that biochars elicit a range of effects on gene expression dependent on intercellular signaling, implicating the method of biochar preparation as a parameter that could be tuned to regulate microbial-dependent soil processes, like nitrogen fixation and pest attack of root crops.

  5. Contribution of the production of quormones to some phenotypic characteristics of Pseudomonas aeruginosa clinical strains.

    PubMed

    Nagant, C; Seil, M; Nachtergael, A; Dulanto, S; Dehaye, J P

    2013-07-01

    The contribution of quorum sensing in some phenotypic and pathogenic characteristics of Pseudomonas aeruginosa was studied. The production of acylhomoserine lactones (AHL) by planktonic cultures of eight clinical and reference strains of P. aeruginosa was evaluated using two biosensors. The adhesion of the bacteria on a surface (Biofilm Ring Test ®, BFRT), their capacity to develop a biofilm (crystal violet staining method, CVSM), their sensitivity to tobramycin and their secretion of proteases or of rhamnolipids were also measured. The production and the release of AHL widely varied among the eight strains. An analysis of the extracts by TLC showed that 3-oxo-C8-HSL, 3-oxo-C10-HSL and 3-oxo-C12-HSL were released by the five strains producing the highest amount of Cn≥6-HSL. The genes lasI and lasR involved in the synthesis and response to 3-oxo-C12-HSL were detected in the genomes of all strains. Two clinical strains had deletions in the lasR gene leading to truncation of the protein. One subpopulation of the PAO1 strain had a major deletion (98 bp) of the lasR gene. Strains with significant mutations of lasR secreted the lowest amount of AHL, probably due to deficiencies in the self-induction and amplification of the synthesis of the lactone. These strains formed a biofilm with low biomass. C4-HSL production also differed among the strains and was correlated with rhamnolipid production and biofilm formation. Whereas the production of AHL varied among P. aeruginosa strains, few correlations were observed with their phenotypic properties except with their ability to form a biofilm.

  6. Biochar and microbial signaling: production conditions determine effects on microbial communication

    PubMed Central

    Masiello, Caroline A.; Chen, Ye; Gao, Xiaodong; Liu, Shirley; Cheng, Hsiao-Ying; Bennett, Matthew R.; Rudgers, Jennifer A.; Wagner, Daniel S.; Zygourakis, Kyriacos; Silberg, Jonathan J.

    2013-01-01

    Charcoal has a long soil residence time, which has resulted in its production and use as a carbon sequestration technique (biochar). A range of biological effects can be triggered by soil biochar that can positively and negatively influence carbon storage, such as changing the decomposition rate of organic matter and altering plant biomass production. Sorption of cellular signals has been hypothesized to underlie some of these effects, but it remains unknown whether the binding of biochemical signals occurs, and if so, on time scales relevant to microbial growth and communication. We examined biochar sorption of N-3-oxo-dodecanoyl-L-homoserine lactone, an acyl-homoserine lactone (AHL) intercellular signaling molecule used by many gram-negative soil microbes to regulate gene expression. We show that wood biochars disrupt communication within a growing multicellular system that is made up of sender cells that synthesize AHL and receiver cells that express green fluorescent protein in response to an AHL signal. However, biochar inhibition of AHL-mediated cell-cell communication varied, with the biochar prepared at 700°C (surface area of 301 m2/g) inhibiting cellular communication 10-fold more than an equivalent mass of biochar prepared at 300°C (surface area of 3 m2/g). These findings provide the first direct evidence that biochars elicit a range of effects on gene expression dependent on intercellular signaling, implicating the method of biochar preparation as a parameter that could be tuned to regulate microbial-dependent soil processes, like nitrogen fixation and pest attack of root crops. PMID:24066613

  7. Evaluation of the regioselective delactonization of tri-sialic acid lactone by in-solution molecular dynamics simulation.

    PubMed

    Chen, Chien-Sheng; Yu, Yi-Ping; Hsu, Chun-Hua; Zou, Wei; Fang, Jim-Min; Wu, Shih-Hsiung

    2012-06-01

    An approximate model for the delactonization of tri-sialic acid lactone is presented with two water-layers that led to neutral hydrolysis of δ-lactone. The hydrolytic reactivity was studied with a 10-ns in-solution molecular dynamics simulation. The initial step of this hydrolysis involves a reactant water nucleophile complex via a proton transfer with another water molecule. Therefore, the probability of water molecules localized at the hydrolytic center correlates to the hydrolysis of δ-lactone. The stepwise delactonization of α2,8-(NeuAc)(3) lactone results/resulted from water concentration discrepancy near the carbonyl carbon of lactones in two water oxygen···carbonyl carbon shells, and the distances of OC···O(water) layers were 2.8 Å and 5.1 Å. Based on in-solution molecular dynamics study, the motion of water molecules over the re-face of the carbonyl groups was used for the quantitative description of the residence probability, p, whose value is 0.11 for lactone I and 0.33 for lactone II. The geometric criteria used to determine the residence statistics are (1) the distance of water-oxygen···carbonyl carbon in less than 5.1 Å and (2) the cone angle, θ, of carbonyl OC···O(water) in the range of 85-115°. As expected, a higher residence probability at lactone II led to its faster hydrolysis. Both the radial g(r) and angular p(θ) pair distribution functions of water oxygen and carbonyl groups of lactones ensure a better surrounding hydration encounter for lactone II. In contrast, water molecules around lactone I are deduced due to a steric hindrance by the turn structure of α2,8-(NeuAc)(3) lactone. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Charcoal disrupts cell-cell communication through multiple mechanisms

    NASA Astrophysics Data System (ADS)

    Gao, X.; Cheng, H. Y.; Liu, S.; Masiello, C. A.; Silberg, J. J.; Del Valle, I.

    2016-12-01

    Microbial cell-cell communication through the release and detection of small signaling molecules is employed by soil microbes to manage many biogeochemically relevant processes including production of biofilms, priming effects on native SOM, and management of methanogenesis and denitrification. Charcoal is a ubiquitous component of soil, entering soil either from natural fire or intentionally amended as biochar. Charcoal's presence in soil introduces spatial and temporal heterogeneity in nutrients and habitats for soil microbes and may trigger a range of biological effects not yet predictable, in part because it interferes with microbial cell-cell communication. We hypothesized that charcoal's alkalinity and large active surface area could affect the lifetime of some chemical compounds that microbes use for cell-cell signaling on times scales relevant to growth and communication. To test this idea, we examined the extent and rate of charcoal quenching of cell-cell communication caused by ten charcoals with a wide range of physicochemical properties. Our measurements focused on signaling mediated by an acyl-homoserine lactone (AHL), N-3-oxo-dodecanoyl-L-homoserine lactone, which is used by many gram-negative bacteria for quorum sensing. Our results from a bioassay and chemical sorption experiments revealed that charcoal can decrease the bioavailable level of AHL through a combination of sorption and pH-dependent hydrolysis of the lactone ring. We found that the kinetics of hydrolysis can exceed those of sorption. These findings implicate charcoal surface area and alkalinity as properties that could be tuned to regulate the degradation rates of cell-cell signaling molecules in soils. We then built a quantitative model that predicts the half-lives of different microbial signaling compounds in the presence of charcoals varying in pH and surface area. Our model results suggest that the effects of charcoal on pH-sensitive bacterial AHL signals will be fundamentally

  9. Pseudomonas aeruginosa Biofilm Formation and Persistence, along with the Production of Quorum Sensing-Dependent Virulence Factors, Are Disrupted by a Triterpenoid Coumarate Ester Isolated from Dalbergia trichocarpa, a Tropical Legume

    PubMed Central

    Pottier, Laurent; Huet, Joelle; Rabemanantsoa, Christian; Kiendrebeogo, Martin; Andriantsimahavandy, Abel; Rasamindrakotroka, Andry; Stévigny, Caroline; Duez, Pierre; El Jaziri, Mondher

    2015-01-01

    Recently, extracts of Dalbergia trichocarpa bark have been shown to disrupt P. aeruginosa PAO1 quorum sensing (QS) mechanisms, which are key regulators of virulence factor expression and implicated in biofilm formation. One of the active compounds has been isolated and identified as oleanolic aldehyde coumarate (OALC), a novel bioactive compound that inhibits the formation of P. aeruginosa PAO1 biofilm and its maintenance as well as the expression of the las and rhl QS systems. Consequently, the production of QS-controlled virulence factors including, rhamnolipids, pyocyanin, elastase and extracellular polysaccharides as well as twitching and swarming motilities is reduced. Native acylhomoserine lactones (AHLs) production is inhibited by OALC but exogenous supply of AHLs does not restore the production of virulence factors by OALC-treated cultures, indicating that OALC exerts its effect beyond AHLs synthesis in the QS pathways. Further experiments provided a significant inhibition of the global virulence factor activator gacA by OALC. OALC disorganizes established biofilm structure and improves the bactericidal activity of tobramycin against biofilm-encapsulated PAO1 cells. Finally, a significant reduction of Caenorhabditis elegans paralysis was recorded when the worms were infected with OALC-pre-treated P. aeruginosa. Taken together, these results show that triterpenoid coumarate esters are suitable chemical backbones to target P. aeruginosa virulence mechanisms. PMID:26186595

  10. Quorum sensing-disrupting coumarin suppressing virulence phenotypes in Vibrio splendidus.

    PubMed

    Zhang, Shanshan; Liu, Ningning; Liang, Weikang; Han, Qingxi; Zhang, Weiwei; Li, Chenghua

    2016-12-09

    In the present study, the effects of an environmental friendly natural reagent coumarin, on the growth and potential virulence factors, as well as its ability to interfere the infection of Vibrio splendidus (Vs), were determined. Coumarin showed no effects on the maximal growth of Vs, and biofilm formation of Vs, while it significantly decreased protease activity and hemolytic activity by 43 and 80%, respectively. Correspondingly, coumarin exhibited an obviously protective effect, with a relative percent survival of 60% upon Apostichopus japonicus from infection by Vs. To preliminarily investigate the mechanism underlining the inhibitory effects, regulation of genes Vsm and Vsh respectively related to protease activity and hemolytic activity by supernatant and supernatant extract containing acyl-homoserine lactones (AHLs) and coumarin was determined. Cell-free supernatant from higher density and its ethyl acetate extract containing AHL signal molecules could respectively upregulate the mRNA level of Vsm by 17.4- and 2.3-fold and Vsh by 7.2- and 5.0-fold, when Vs was at lower cell density. However, coumarin could reduce the stimulatory effects of both the supernatant and its ethyl acetate extract. Combining all the results in our study, it was suggested that coumarin could be considered as an alternative to be used for controlling infection of Vs, downregulating the expression of potential virulence factors through interfering the AHL-mediated pathways.

  11. Investigating the effect of antibiotics on quorum sensing with whole-cell biosensing systems.

    PubMed

    Struss, Anjali K; Pasini, Patrizia; Flomenhoft, Deborah; Shashidhar, Harohalli; Daunert, Sylvia

    2012-04-01

    Quorum sensing (QS) allows bacteria to communicate with one another by means of QS signaling molecules and control certain behaviors in a group-based manner, including pathogenicity and biofilm formation. Bacterial gut microflora may play a role in inflammatory bowel disease pathogenesis, and antibiotics are one of the available therapeutic options for Crohn's disease. In the present study, we employed genetically engineered bioluminescent bacterial whole-cell sensing systems as a tool to evaluate the ability of antibiotics commonly employed in the treatment of chronic inflammatory conditions to interfere with QS. We investigated the effect of ciprofloxacin, metronidazole, and tinidazole on quorum sensing. Several concentrations of individual antibiotics were allowed to interact with two different types of bacterial sensing cells, in both the presence and absence of a fixed concentration of N-acylhomoserine lactone (AHL) QS molecules. The antibiotic effect was then determined by monitoring the biosensor's bioluminescence response. Ciprofloxacin, metronidazole, and tinidazole exhibited a dose-dependent augmentation in the response of both bacterial sensing systems, thus showing an AHL-like effect. Additionally, such an augmentation was observed, in both the presence and absence of AHL. The data obtained indicate that ciprofloxacin, metronidazole, and tinidazole may interfere with bacterial communication systems. The results suggest that these antibiotics, at the concentrations tested, may themselves act as bacterial signaling molecules. The beneficial effect of these antibiotics in the treatment of intestinal inflammation may be due, at least in part, to their effect on QS-related bacterial behavior in the gut.

  12. Construction and phenotypic characterization of M68, an RruI quorum sensing knockout mutant of the photosynthetic alphaproteobacterium Rhodospirillum rubrum.

    PubMed

    Condori, Sandra; Atkinson, Steve; Leys, Natalie; Wattiez, Ruddy; Mastroleo, Felice

    2016-06-01

    Many bacterial species communicate using a complex system known as quorum sensing (QS) in which gene expression is controlled in response to cell density. In this study an N-acylhomoserine lactone (AHL) synthase (Rru_A3396) knockout mutant (M68) of Rhodospirillum rubrum S1H (WT) was constructed and characterized phenotypically under light anaerobic conditions. Results showed that R. rubrum WT produces unsubstituted, 3-OH and 3-oxo-substituted AHLs with acyl chains ranging from 4 to 14 carbons, with 3-OH-C8 being the most abundant. Growth, pigment content and swimming motility were found to be under the control of this LuxI-type QS system. In addition, cultivation in a low shear environment put forward the aggregative phenotype of M68 and linked biofilm formation to QS in R. rubrum S1H. Interestingly, QS-mutant M68 continued to produce decreased levels of 3-OH-C8-HSL, probably due to the presence of an extra HdtS-type AHL synthase.

  13. Pseudomonas aeruginosa Biofilm Formation and Persistence, along with the Production of Quorum Sensing-Dependent Virulence Factors, Are Disrupted by a Triterpenoid Coumarate Ester Isolated from Dalbergia trichocarpa, a Tropical Legume.

    PubMed

    Rasamiravaka, Tsiry; Vandeputte, Olivier M; Pottier, Laurent; Huet, Joelle; Rabemanantsoa, Christian; Kiendrebeogo, Martin; Andriantsimahavandy, Abel; Rasamindrakotroka, Andry; Stévigny, Caroline; Duez, Pierre; El Jaziri, Mondher

    2015-01-01

    Recently, extracts of Dalbergia trichocarpa bark have been shown to disrupt P. aeruginosa PAO1 quorum sensing (QS) mechanisms, which are key regulators of virulence factor expression and implicated in biofilm formation. One of the active compounds has been isolated and identified as oleanolic aldehyde coumarate (OALC), a novel bioactive compound that inhibits the formation of P. aeruginosa PAO1 biofilm and its maintenance as well as the expression of the las and rhl QS systems. Consequently, the production of QS-controlled virulence factors including, rhamnolipids, pyocyanin, elastase and extracellular polysaccharides as well as twitching and swarming motilities is reduced. Native acylhomoserine lactones (AHLs) production is inhibited by OALC but exogenous supply of AHLs does not restore the production of virulence factors by OALC-treated cultures, indicating that OALC exerts its effect beyond AHLs synthesis in the QS pathways. Further experiments provided a significant inhibition of the global virulence factor activator gacA by OALC. OALC disorganizes established biofilm structure and improves the bactericidal activity of tobramycin against biofilm-encapsulated PAO1 cells. Finally, a significant reduction of Caenorhabditis elegans paralysis was recorded when the worms were infected with OALC-pre-treated P. aeruginosa. Taken together, these results show that triterpenoid coumarate esters are suitable chemical backbones to target P. aeruginosa virulence mechanisms.

  14. Novel Mouse Model of Chronic Pseudomonas aeruginosa Lung Infection Mimicking Cystic Fibrosis

    PubMed Central

    Hoffmann, Nadine; Rasmussen, Thomas Bovbjerg; Jensen, PeterØstrup; Stub, Charlotte; Hentzer, Morten; Molin, Søren; Ciofu, Oana; Givskov, Michael; Johansen, Helle Krogh; Høiby, Niels

    2005-01-01

    Pseudomonas aeruginosa causes a chronic infection in the lungs of cystic fibrosis (CF) patients by establishing an alginate-containing biofilm. The infection has been studied in several animal models; however, most of the models required artificial embedding of the bacteria. We present here a new pulmonary mouse model without artificial embedding. The model is based on a stable mucoid CF sputum isolate (NH57388A) with hyperproduction of alginate due to a deletion in mucA and functional N-acylhomoserine lactone (AHL)-based quorum-sensing systems. Chronic lung infection could be established in both CF mice (CftrtmlUnc−/−) and BALB/c mice, as reflected by the detection of a high number of P. aeruginosa organisms in the lung homogenates at 7 days postinfection and alginate biofilms, surrounded by polymorphonuclear leukocytes in the alveoli. In comparison, both an AHL-producing nonmucoid revertant (NH57388C) from the mucoid isolate (NH57388A) and a nonmucoid isolate (NH57388B) deficient in AHL were almost cleared from the lungs of the mice. This model, in which P. aeruginosa is protected against the defense system of the lung by alginate, is similar to the clinical situation. Therefore, the mouse model provides an improved method for evaluating the interaction between mucoid P. aeruginosa, the host, and antibacterial therapy. PMID:15784597

  15. A genetic circuit system based on quorum sensing signaling for directed evolution of quorum-quenching enzymes.

    PubMed

    Kim, Jin-Hyun; Lee, Sang-Chul; Kyeong, Hyun-Ho; Kim, Hak-Sung

    2010-08-16

    Quorum sensing is a cell-cell communication mechanism that is involved in the regulation of biological functions such as luminescence, virulence, and biofilm formation. Quorum-quenching enzymes, which interrupt quorum-sensing signaling through degradation of quorum-sensing molecules, have emerged as a new approach to controlling and preventing bacterial virulence and pathogenesis. In an effort to develop quorum-quenching enzymes with improved catalytic activities, a genetic circuit system based on acylhomoserine-lactone (AHL)-mediated quorum-sensing signaling was constructed. The genetic circuit system was composed of lux-R, lux-I promoter, beta-lactamase, and beta-lactamase inhibitor, and designed to confer antibiotic resistance on host cells expressing an AHL-degrading enzyme, thereby enabling rapid screening of quorum-quenching enzymes. To demonstrate the utility of the genetic circuit system, we attempted the directed evolution of the AHL hydrolase from Bacillus sp. The genetic circuit system was shown to be effective in screening of quorum-quenching enzymes with high catalytic efficiency. From these results it is expected that the genetic circuit system can be widely used for the isolation and directed evolution of quorum-quenching enzymes with greater potential.

  16. The pharmacokinetics and conversion of the lactone to the carboxylate forms of ginkgolide B in rat plasma.

    PubMed

    Wang, Dian-Lei; Peng, Dai-Yin; Tao, Xiu-Hua; Cao, Yin; Chen, Wei-Dong; Liang, Yan; Xie, Lin; Liu, Xiao-Dong

    2013-01-01

    Ginkgolide B consists of three lactone groups, which may undergo hydrolysis, and lead to the rings opening in aqueous solution with different pHs. From mechanisms of pharmacological activity in vivo, the lactone appears to be the active form of the drug. Pharmacokinetics of lactone form (GB-lac) and the total of the lactone and carboxylate form (GB-tot) of ginkgolide B were investigated after intravenous administration of a dose of 4 mg/kg ginkgolide B. The rate of lactone hydrolysis was also studied in plasma in vitro. After intravenous administration, ginkgolide B in the original form was converted to its carboxylate form under simulated physiological conditions. The AUC0 - ∞ of GB-lac constituted 63.5 ± 17.4% of the AUC0 - ∞ of GB-tot. The ratio of average cumulation of excretion of lactone to carboxylate reached approximately 1 to 1 in urine. From the equilibrium of lactone hydrolysis in rat plasma in vitro, the k obs was - 0.0176 min(- 1) and t 1/2 was 39.38 min. In conclusion, the equilibrium existed between lactone of ginkgolide B and its carboxylate form in vivo at physiological pH, which suggested that more attention should be focused on the original and the ionization forms of ginkgolide B and the conversion of the lactone into carboxylate in vivo.

  17. Lactonization and protonation of gluconic acid: a thermodynamicand kinetic study by potentiometry, nmr and esi-ms

    SciTech Connect

    Zhang, Z.; Gibson, P.; Clark, S.B.; Tian, G.; Zanonato, P.; Rao, L.

    2007-01-10

    In acidic aqueous solutions, gluconate protonation is coupled with lactonization of gluconic acid. With the decrease of pC{sub H}, two lactones ({delta}/{gamma}) are sequentially formed. The {delta}-lactone forms more readily than the {gamma}-lactone. In 0.1 M gluconate solutions, if pC{sub H} is above 2.5, only the {delta}-lactone is generated. When pC{sub H} is decreased below 2.0, the formation of the {gamma}-lactone is observable although the {delta}-lactone predominates. At I = 0.1 M NaClO{sub 4} and room temperature, the deprotonation constant of the carboxylic group, using the NMR technique, was determined to be log K{sub a} = 3.30 {+-} 0.02; the {delta}-lactonization constant, by the batch potentiometric titrations, was obtained to be log K{sub L} = - (0.54 {+-} 0.04). Using ESI-MS, the rate constants of the {delta}-lactonization and the hydrolysis at pC{sub H} {approx} 5.0 were estimated to be k{sub 1} = 3.2 x 10{sup -5} s{sup -1} and k{sup -1} = 1.1 x 10{sup -4} s{sup -1}, respectively.

  18. Short communication: Macrocyclic lactone residues in butter from Brazilian markets.

    PubMed

    Macedo, Fabio; Marsico, Eliane Teixeira; Conte-Júnior, Carlos Adam; de Almeida Furtado, Leonardo; Brasil, Taila Figueredo; Pereira Netto, Annibal Duarte

    2015-06-01

    Macrocyclic lactones (ML) are commonly used in drug formulations for the treatment of parasites in cattle. In Brazil, except for drugs (or formulations) with long-term (half-life) effects, ML are registered for use in bovines. Indiscriminate use of ML may result in the presence of residues in milk and dairy products due to their lipophilic properties and thermal stability. This study applied a method of liquid chromatography with fluorimetric detection, recently developed and validated for the determination of residues of abamectin, doramectin, ivermectin, and moxidectin in butter. The method was applied to 38 samples of commercial butter purchased in the metropolitan area of Rio de Janeiro, Brazil, between June and September 2013, analyzed in triplicate. Ivermectin was detected in 89.5% of the samples, with concentrations between 0.3 and 119.4 µg/kg; 76.3% of the samples contained doramectin (0.6 to 64.7 µg/kg) and 55.2% contained abamectin (0.7 to 4.5 µg/kg). Most butter samples (76.3%) contained residues of more than 1 ML; however, no residues of moxidectin were detected. The results showed a high incidence of the presence of avermectins in butter samples. Butter is not included in the Brazilian National Plan for Control of Residues and Contaminants in Animal Products. As ML residues concentrate in lipophilic compounds, butter and other fatty dairy products should be screened for the presence of ML residues.

  19. Dermatobia hominis: Potencial risk of resistance to macrocyclic lactones.

    PubMed

    das Neves, José Henrique; Carvalho, Nadino; Amarante, Alessandro F T

    2015-09-15

    Dermatobia hominis is an ectoparasite that infests various species of mammals, including cattle, impairing the quality of cowhides and leather. After observing natural infestation with D. hominis larvae in cattle on two farms in the state of São Paulo, Brazil, we evaluated the efficacy of two macrocyclic lactones, ivermectin and moxidectin, against this parasite. The drugs were administered to 10 animals in each group, following the manufacturer's instructions. The groups were: Group 1-treated with ivermectin (0.2mg/kg of body weight (BW)); Group 2-treated with moxidectin (0.2mg/kg BW); and Group 3-control (untreated). On the farm in Pardinho, a total of 12 and 16 live larvae were found in 6 and in 8 animals 10 days after the treatment with ivermectin and moxidectin, respectively, while in the control group 4 bovines had a total of 7 live larvae. On the farm in Anhembi, 2, 4 and 6 live larvae were extracted from ivermectin, moxidectin and control groups, respectively, after the treatment. This is the first report of the presence of live D. hominis larvae after the treatment of cattle with ivermectin and moxidectin in Brazil.

  20. Anti-inflammatory lanostanoids and lactone derivatives from Antrodia camphorata.

    PubMed

    Liaw, Chih-Chuang; Chen, Yu-Chang; Huang, Guan-Jhong; Tsai, Yao-Ching; Chien, Shih-Chang; Wu, Jyh-Horng; Wang, Sheng-Yang; Chao, Louis Kuoping; Sung, Ping-Jyun; Huang, Hui-Chi; Kuo, Yueh-Hsiung

    2013-04-26

    Four new lanostanoids, ethyl lucidenate A (1), ethyl lucidenate F (2), 15-O-acetylganolucidate A (3), and 3,11,15,23-tetraoxo-27ξ-lanosta-8,16-dien-26-oic acid (4), and two new lactone derivatives, 5-hydroxy-5-(methoxymethyl)-4-methylfuran-2(5H)-one (5) and 3-(4-methoxy-2-oxo-2H-pyran-6-yl)propanoic acid (6), together with four known compounds, 11α-hydroxy-3,7-dioxolanost-8,24(E)-dien-26- oic acid (7), 3,7,11-trioxo-5α-lanosta-8,24(E)-dien-26-oic acid (8), methyl 3,7,11,12,15,23-hexaoxo-5α-lanost-8-en-26-oate (9), and ethyl 3,7,11,12,15,23-hexaoxo-5α-lanost-8-en-26-oate (10), were characterized from Antrodia camphorata. The structures of these new compounds were determined by analysis of their spectroscopic data, including 1D and 2D NMR experiments. Ten components were evaluated for anti-inflammatory activity by examining their effect on LPS-iNOS-dependent NO production in murine macrophage (RAW 264.7) cells. Among them, compounds 1, 3, 7, 8, 9, and 10 significantly suppressed the NO concentration in LPS-treated RAW 264.7 cells with IC50 values ≤ 10 μM.

  1. In Vitro Antiplasmodial Activity of Sesquiterpene Lactones from Ambrosia tenuifolia

    PubMed Central

    Sülsen, V.; Gutierrez Yappu, D.; Laurella, L.; Anesini, C.; Gimenez Turba, A.; Martino, V.; Muschietti, L.

    2011-01-01

    The in vitro antiplasmodial activity of Ambrosia tenuifolia organic extract and its isolated sesquiterpene lactones, psilostachyin and peruvin, has been evaluated against Plasmodium falciparum F32 and W2 strains. The cytotoxicity of both compounds was determined on lymphoid cells, and their corresponding selectivity indexes (SIs) were calculated. Peruvin was the most active compound on F32 strain of P. falciparum with a 50% inhibitory concentration value (IC50) of 0.3 μg/mL (1.1 μM) whereas psilostachyin showed activity on both strains (IC50 = 0.6 (2.1 μM) and 1.8 μg/mL (6.4 μM)). Fifty percent cytotoxic concentration (CC50) values (48 h) were 6.8 μg/mL (24.3 μM) and 10.0 μg/mL (37.9 μM) for psilostachyin and peruvin, respectively. PMID:21716685

  2. Biosynthesis of Costunolide, Dihydrocostunolide, and Leucodin. Demonstration of Cytochrome P450-Catalyzed Formation of the Lactone Ring Present in Sesquiterpene Lactones of Chicory

    PubMed Central

    de Kraker, Jan-Willem; Franssen, Maurice C.R.; Joerink, Maaike; de Groot, Aede; Bouwmeester, Harro J.

    2002-01-01

    Chicory (Cichorium intybus) is known to contain guaianolides, eudesmanolides, and germacranolides. These sesquiterpene lactones are postulated to originate from a common germacranolide, namely (+)-costunolide. Whereas a pathway for the formation of germacra-1(10),4,11(13)-trien-12-oic acid from farnesyl diphosphate had previously been established, we now report the isolation of an enzyme activity from chicory roots that converts the germacrene acid into (+)-costunolide. This (+)-costunolide synthase catalyzes the last step in the formation of the lactone ring present in sesquiterpene lactones and is dependent on NADPH and molecular oxygen. Incubation of the germacrene acid in the presence of 18O2 resulted in the incorporation of one atom of 18O into (+)-costunolide. The label was situated at the ring oxygen atom. Hence, formation of the lactone ring most likely occurs via C6-hydroxylation of the germacrene acid and subsequent attack of this hydroxyl group at the C12-atom of the carboxyl group. Blue light-reversible CO inhibition and experiments with cytochrome P450 inhibitors demonstrated that the (+)-costunolide synthase is a cytochrome P450 enzyme. In addition, enzymatic conversion of (+)-costunolide into 11(S),13-dihydrocostunolide and leucodin, a guaianolide, was detected. The first-mentioned reaction involves an enoate reductase, whereas the formation of leucodin from (+)-costunolide probably involves more than one enzyme, including a cytochrome P450 enzyme. PMID:12011356

  3. Signal Destruction Tunes the Zone of Activation in Spatially Distributed Signaling Networks.

    PubMed

    Silva, Kalinga Pavan; Chellamuthu, Prithiviraj; Boedicker, James Q

    2017-03-14

    Diverse microbial communities coordinate group behaviors through signal exchange, such as the exchange of acyl-homoserine lactones (AHLs) by Gram-negative bacteria. Cellular communication is prone to interference by neighboring microbes. One mechanism of interference is signal destruction through the production of an enzyme that cleaves the signaling molecule. Here we examine the ability of one such interference enzyme, AiiA, to modulate signal propagation in a spatially distributed system of bacteria. We have developed an experimental assay to measure signal transduction and implement a theoretical model of signaling dynamics to predict how the system responds to interference. We show that titration of an interfering strain into a signaling network tunes the spatial range of activation over the centimeter length scale, quantifying the robustness of the signaling network to signal destruction and demonstrating the ability to program systems-level responses of spatially heterogeneous cellular networks.

  4. Grapefruit juice and its furocoumarins inhibits autoinducer signaling and biofilm formation in bacteria.

    PubMed

    Girennavar, Basavaraj; Cepeda, Martha L; Soni, Kamlesh A; Vikram, Amit; Jesudhasan, Palmy; Jayaprakasha, G K; Pillai, Suresh D; Patil, Bhimanagouda S

    2008-07-15

    Cell-to-cell communications in bacteria mediated by small diffusible molecules termed as autoinducers (AI) are known to influence gene expression and pathogenicity. Oligopeptides and N-acylhomoserine lactones (AHL) are major AI molecules involved in intra-specific communication in gram-positive and gram-negative bacteria respectively, whereas boronated-diester molecules (AI-2) are involved in inter-specific communication among both gram-positive and gram-negative bacteria. Naturally occurring furocoumarins from grapefruit showed >95% inhibition of AI-1 and AI-2 activities based on the Vibrio harveyi based autoinducer bioassay. Grapefruit juice and furocoumarins also inhibited biofilm formation by Escherichia coli O157:H7, Salmonella typhimurium and Pseudomonas aeruginosa. These results suggest that grape fruit juice and furocoumarins could serve as a source to develop bacterial intervention strategies targeting microbial cell signaling processes.

  5. Marine Microbiological Enzymes: Studies with Multiple Strategies and Prospects

    PubMed Central

    Wang, Yan; Song, Qinghao; Zhang, Xiao-Hua

    2016-01-01

    Marine microorganisms produce a series of promising enzymes that have been widely used or are potentially valuable for our daily life. Both classic and newly developed biochemistry technologies have been broadly used to study marine and terrestrial microbiological enzymes. In this brief review, we provide a research update and prospects regarding regulatory mechanisms and related strategies of acyl-homoserine lactones (AHL) lactonase, which is an important but largely unexplored enzyme. We also detail the status and catalytic mechanism of the main types of polysaccharide-degrading enzymes that broadly exist among marine microorganisms but have been poorly explored. In order to facilitate understanding, the regulatory and synthetic biology strategies of terrestrial microorganisms are also mentioned in comparison. We anticipate that this review will provide an outline of multiple strategies for promising marine microbial enzymes and open new avenues for the exploration, engineering and application of various enzymes. PMID:27669268

  6. Marine Microbiological Enzymes: Studies with Multiple Strategies and Prospects.

    PubMed

    Wang, Yan; Song, Qinghao; Zhang, Xiao-Hua

    2016-09-22

    Marine microorganisms produce a series of promising enzymes that have been widely used or are potentially valuable for our daily life. Both classic and newly developed biochemistry technologies have been broadly used to study marine and terrestrial microbiological enzymes. In this brief review, we provide a research update and prospects regarding regulatory mechanisms and related strategies of acyl-homoserine lactones (AHL) lactonase, which is an important but largely unexplored enzyme. We also detail the status and catalytic mechanism of the main types of polysaccharide-degrading enzymes that broadly exist among marine microorganisms but have been poorly explored. In order to facilitate understanding, the regulatory and synthetic biology strategies of terrestrial microorganisms are also mentioned in comparison. We anticipate that this review will provide an outline of multiple strategies for promising marine microbial enzymes and open new avenues for the exploration, engineering and application of various enzymes.

  7. Structure-Based Function Discovery of an Enzyme for the Hydrolysis of Phosphorylated Sugar Lactones

    PubMed Central

    Xiang, Dao Feng; Kolb, Peter; Fedorov, Alexander A.; Xu, Chengfu; Fedorov, Elena V.; Narindoshivili, Tamari; Williams, Howard J.; Shoichet, Brian K.; Almo, Steven C.; Raushel, Frank M.

    2012-01-01

    Two enzymes of unknown function from the cog1735 subset of the amidohydrolase superfamily (AHS), LMOf2365_2620 (Lmo2620) from Listeria monocytogenes str. 4b F2365 and Bh0225 from Bacillus halodurans C-125, were cloned, expressed and purified to homogeneity. The catalytic functions of these two enzymes were interrogated by an integrated strategy encompassing bioinformatics, computational docking to three-dimensional crystal structures, and library screening. The three-dimensional structure of Lmo2620 was determined at a resolution of 1.6 Å with two phosphates and a binuclear zinc center in the active site. The proximal phosphate bridges the binuclear metal center and is 7.1 Å away from the distal phosphate. The distal phosphate hydrogen bonds with Lys-242, Lys-244, Arg-275 and Tyr-278. Enzymes within cog1735 of the AHS have previously been shown to catalyze the hydrolysis of substituted lactones. Computational docking of the high energy intermediate (HEI) form of the KEGG database to the three-dimensional structure of Lmo2620 highly enriched anionic lactones versus other candidate substrates. The active site structure and the computational docking results suggested that probable substrates would likely include phosphorylated sugar lactones. A small library of diacid sugar lactones and phosphorylated sugar lactones was synthesized and tested for substrate activity with Lmo2620 and Bh0225. Two substrates were identified for these enzymes, d-lyxono-1,4-lactone-5-phosphate and l-ribono-1,4-lactone-5-phosphate. The kcat/Km values for the cobalt-substituted enzymes with these substrates are ~105 M−1 s−1. PMID:22313111

  8. Structure-based function discovery of an enzyme for the hydrolysis of phosphorylated sugar lactones.

    PubMed

    Xiang, Dao Feng; Kolb, Peter; Fedorov, Alexander A; Xu, Chengfu; Fedorov, Elena V; Narindoshivili, Tamari; Williams, Howard J; Shoichet, Brian K; Almo, Steven C; Raushel, Frank M

    2012-02-28

    Two enzymes of unknown function from the cog1735 subset of the amidohydrolase superfamily (AHS), LMOf2365_2620 (Lmo2620) from Listeria monocytogenes str. 4b F2365 and Bh0225 from Bacillus halodurans C-125, were cloned, expressed, and purified to homogeneity. The catalytic functions of these two enzymes were interrogated by an integrated strategy encompassing bioinformatics, computational docking to three-dimensional crystal structures, and library screening. The three-dimensional structure of Lmo2620 was determined at a resolution of 1.6 Å with two phosphates and a binuclear zinc center in the active site. The proximal phosphate bridges the binuclear metal center and is 7.1 Å from the distal phosphate. The distal phosphate hydrogen bonds with Lys-242, Lys-244, Arg-275, and Tyr-278. Enzymes within cog1735 of the AHS have previously been shown to catalyze the hydrolysis of substituted lactones. Computational docking of the high-energy intermediate form of the KEGG database to the three-dimensional structure of Lmo2620 highly enriched anionic lactones versus other candidate substrates. The active site structure and the computational docking results suggested that probable substrates would likely include phosphorylated sugar lactones. A small library of diacid sugar lactones and phosphorylated sugar lactones was synthesized and tested for substrate activity with Lmo2620 and Bh0225. Two substrates were identified for these enzymes, D-lyxono-1,4-lactone-5-phosphate and l-ribono-1,4-lactone-5-phosphate. The k(cat)/K(m) values for the cobalt-substituted enzymes with these substrates are ~10(5) M(-1) s(-1).

  9. Membrane anchoring of diacylglycerol-lactones substituted with rigid hydrophobic acyl domains correlates with biological activities

    PubMed Central

    Raifman, Or; Kolusheva, Sofiya; Comin, Maria J.; Kedei, Noemi; Lewin, Nancy E.; Blumberg, Peter M.; Marquez, Victor E.; Jelinek, Raz

    2009-01-01

    Summary Synthetic diacylglycerol lactones (DAG-lactones) are effective modulators of critical cellular signaling pathways, downstream of the lipophilic second messenger diacylglycerol, that activate a host of protein kinase C (PKC) isozymes as well as other non-kinase proteins that share with PKC similar C1 membrane-targeting domains. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study characterizes the membrane interactions and bilayer anchoring of a series of DAG-lactones in which the hydrophobic moiety is a “molecular rod”, namely a rigid 4-[2-(R-phenyl)ethynyl]benzoate moiety in the acyl position. Application of assays employing chromatic biomimetic vesicles and biophysical techniques reveals that the mode of membrane anchoring of the DAG-lactone derivatives was markedly affected by the presence of the hydrophobic diphenyl rod and by the size of the functional unit displayed at the terminus of the rod. Two primary mechanisms of interaction were observed: surface binding of the DAG-lactones at the lipid/water interface and deep insertion of the ligands into the alkyl core of the lipid bilayer. These membrane-insertion properties could explain the different patterns of PKC translocation from cytosol to membranes induced by the molecular-rod DAG-lactones. This investigation emphasizes that the side-residues of DAG-lactones, rather than simply conferring hydrophobicity, profoundly influence membrane interactions and in that fashion may further contribute to the diversity of biological actions of these synthetic biomimetic ligands. PMID:19961537

  10. The formation of wine lactone from grape-derived secondary metabolites.

    PubMed

    Giaccio, Joanne; Capone, Dimitra L; Håkansson, Anders E; Smyth, Heather E; Elsey, Gordon M; Sefton, Mark A; Taylor, Dennis K

    2011-01-26

    Wine lactone (i.e., 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one, 1a/1b) was formed hydrolytically at wine pH from both racemic (E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid (3) and the corresponding glucose ester 2a at 45 °C but at room temperature was only formed from the acid 3. The glucose ester does not appear to be a significant precursor for the formation of wine lactone in wine. The slow formation of wine lactone from the free acid 3 indicates that the acid is not likely to be an important precursor to wine lactone in young wines unless present in high concentration (≫ 1 mg/L), but could be a significant precursor to wine lactone in wine that is several years old. The wine lactone formed in hydrolysates of the (6R)-enantiomer of 3 was partially enriched in the (3S,3aS,7aR)-enantiomer 1a when the hydrolysis was conducted at pH 3.2 and 100 °C in a closed vessel or under simultaneous distillation-extraction (SDE) conditions, and the enantiomeric excess (ee) varied from 5 to 22%. Hydrolysis of (6R)-3 in sealed ampules at 45 °C and at pH 3.0, 3.2, or 3.4 gave near-racemic wine lactone, but when the hydrolyses were conducted at room temperature, the product was enriched in the (3S,3aS,7aR)-enantiomer 1a and the ee was greater at higher pH (up to 60% at pH 3.4).

  11. Where are signal molecules likely to be located in anaerobic granular sludge?

    PubMed

    Feng, Huajun; Ding, Yangcheng; Wang, Meizhen; Zhou, Guanglan; Zheng, Xin; He, Hongzhen; Zhang, Xueqin; Shen, Dongsheng; Shentu, Jiali

    2014-03-01

    Quorum sensing is a concentration-sensing mechanism that plays a vital role in sludge granulation. In this study, the regularities of distribution of different signal molecules, including intra- and interspecific signal molecules (diffusible signal factor, DSF), interspecific signal molecules (autoinducter-2, AI-2) and intraspecific signal molecules (acyl-homoserine lactones, AHLs), from three types of anaerobic granular sludge were investigated. The results showed that 70-90% of DSF was distributed in sludge, while AI-2 in the Water phase accounted for over 80% of the total content. Interestingly, there was a positive correlation between DSF and AI-2, which played opposite roles in granulation. Moreover, more than 55% of short and medium acyl chain AHLs tended to spread in aqueous water, while the long acyl chain AHLs were closer to granular sludge than the short and medium acyl chain AHLs. With the exception of one type of sludge, the percentage of long acyl chain AHLs in the sludge phase was greater than 70%. The different distributions of signal molecules were primarily determined based on their physicochemical properties, including molecular weight and solubility in water or organic solutions. In addition, the basic properties of sludge, such as the granular level or the production of EPS, were closely related to the diversity, distribution and concentration of signal molecules. As a medium in granulation, extracellular polymeric substances production was regulated by different signal molecules from different parts of anaerobic granular sludge. This study provides a foundation for investigation of quorum sensing in the system of anaerobic granular sludge.

  12. At a supra-physiological concentration, human sexual hormones act as quorum-sensing inhibitors.

    PubMed

    Beury-Cirou, Amélie; Tannières, Mélanie; Minard, Corinne; Soulère, Laurent; Rasamiravaka, Tsiry; Dodd, Robert H; Queneau, Yves; Dessaux, Yves; Guillou, Catherine; Vandeputte, Olivier M; Faure, Denis

    2013-01-01

    N-acylhomoserine lactone (AHL)-mediated quorum-sensing (QS) regulates virulence functions in plant and animal pathogens such as Agrobacterium tumefaciens and Pseudomonas aeruginosa. A chemolibrary of more than 3500 compounds was screened using two bacterial AHL-biosensors to identify QS-inhibitors (QSIs). The purity and structure of 15 QSIs selected through this screening were verified using HPLC MS/MS tools and their activity tested on the A. tumefaciens and P. aeruginosa bacterial models. The IC50 value of the identified QSIs ranged from 2.5 to 90 µg/ml, values that are in the same range as those reported for the previously identified QSI 4-nitropyridine-N-oxide (IC50 24 µg/ml). Under the tested culture conditions, most of the identified QSIs did not exhibit bacteriostatic or bactericidal activities. One third of the tested QSIs, including the plant compound hordenine and the human sexual hormone estrone, decreased the frequency of the QS-regulated horizontal transfer of the tumor-inducing (Ti) plasmid in A. tumefaciens. Hordenine, estrone as well as its structural relatives estriol and estradiol, also decreased AHL accumulation and the expression of six QS-regulated genes (lasI, lasR, lasB, rhlI, rhlR, and rhlA) in cultures of the opportunist pathogen P. aeruginosa. Moreover, the ectopic expression of the AHL-receptors RhlR and LasR of P. aeruginosa in E. coli showed that their gene-regulatory activity was affected by the QSIs. Finally, modeling of the structural interactions between the human hormones and AHL-receptors LasR of P. aeruginosa and TraR of A. tumefaciens confirmed the competitive binding capability of the human sexual hormones. This work indicates potential interferences between bacterial and eukaryotic hormonal communications.

  13. At a Supra-Physiological Concentration, Human Sexual Hormones Act as Quorum-Sensing Inhibitors

    PubMed Central

    Beury-Cirou, Amélie; Tannières, Mélanie; Minard, Corinne; Soulère, Laurent; Rasamiravaka, Tsiry; Dodd, Robert H.; Queneau, Yves; Dessaux, Yves; Guillou, Catherine; Vandeputte, Olivier M.; Faure, Denis

    2013-01-01

    N-Acylhomoserine lactone (AHL)-mediated quorum-sensing (QS) regulates virulence functions in plant and animal pathogens such as Agrobacterium tumefaciens and Pseudomonas aeruginosa. A chemolibrary of more than 3500 compounds was screened using two bacterial AHL-biosensors to identify QS-inhibitors (QSIs). The purity and structure of 15 QSIs selected through this screening were verified using HPLC MS/MS tools and their activity tested on the A. tumefaciens and P. aeruginosa bacterial models. The IC50 value of the identified QSIs ranged from 2.5 to 90 µg/ml, values that are in the same range as those reported for the previously identified QSI 4-nitropyridine-N-oxide (IC50 24 µg/ml). Under the tested culture conditions, most of the identified QSIs did not exhibit bacteriostatic or bactericidal activities. One third of the tested QSIs, including the plant compound hordenine and the human sexual hormone estrone, decreased the frequency of the QS-regulated horizontal transfer of the tumor-inducing (Ti) plasmid in A. tumefaciens. Hordenine, estrone as well as its structural relatives estriol and estradiol, also decreased AHL accumulation and the expression of six QS-regulated genes (lasI, lasR, lasB, rhlI, rhlR, and rhlA) in cultures of the opportunist pathogen P. aeruginosa. Moreover, the ectopic expression of the AHL-receptors RhlR and LasR of P. aeruginosa in E. coli showed that their gene-regulatory activity was affected by the QSIs. Finally, modeling of the structural interactions between the human hormones and AHL-receptors LasR of P. aeruginosa and TraR of A. tumefaciens confirmed the competitive binding capability of the human sexual hormones. This work indicates potential interferences between bacterial and eukaryotic hormonal communications. PMID:24376718

  14. Identification and characterization of new LuxR/LuxI-type quorum sensing systems from metagenomic libraries

    PubMed Central

    Hao, Youai; Winans, Stephen C.; Glick, Bernard R.; Charles, Trevor C.

    2010-01-01

    Summary Quorum sensing (QS) cell–cell communication systems are utilized by bacteria to coordinate their behaviour according to cell density. Several different types of QS signal molecules have been identified, among which acyl-homoserine lactones (AHLs) produced by Proteobacteria have been studied to the greatest extent. Although QS has been studied extensively in cultured microorganisms, little is known about the QS systems of uncultured microorganisms and the roles of these systems in microbial communities. To extend our knowledge of QS systems and to better understand the signalling that takes place in the natural environment, metagenomic libraries constructed using DNA from activated sludge and soil were screened, using an Agrobacterium biosensor strain, for novel QS synthase genes. Three cosmids (QS6-1, QS10-1 and QS10-2) that encode the production of QS signals were identified and DNA sequence analysis revealed that all three clones encode a novel luxI family AHL synthase and a luxR family transcriptional regulator. Thin layer chromatography revealed that these LuxI homologue proteins are able to synthesize multiple AHL signals. Tandem mass spectrometry analysis revealed that LuxIQS6-1 directs the synthesis of at least three AHLs, 3-O-C14:1 HSL, 3-O-C16:1 HSL and 3-O-C14 HSL; LuxIQS10-1 directs the synthesis of at least 3-O-C12 HSL and 3-O-C14 HSL; while LuxIQS10-2 directs the synthesis of at least C8 HSL and C10 HSL. Two possible new AHLs, C14:3 HSL and (?)-hydroxymethyl-3-O-C14 HSL, were also found to be synthesized by LuxIQS6-1. PMID:19735279

  15. Rhodotorula mucilaginosa, a quorum quenching yeast exhibiting lactonase activity isolated from a tropical shoreline.

    PubMed

    Ghani, Norshazliza Ab; Sulaiman, Joanita; Ismail, Zahidah; Chan, Xin-Yue; Yin, Wai-Fong; Chan, Kok-Gan

    2014-04-09

    Two microbial isolates from a Malaysian shoreline were found to be capable of degrading N-acylhomoserine lactones. Both Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry and 18S rDNA phylogenetic analyses confirmed that these isolates are Rhodotorula mucilaginosa. Quorum quenching activities were detected by a series of bioassays and rapid resolution liquid chromatography analysis. The isolates were able to degrade various quorum sensing molecules namely N-hexanoyl-L-homoserine lactone (C6-HSL), N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-L-homoserine lactone (3-hydroxy-C6-HSL). Using a relactonisation assay to verify the quorum quenching mechanism, it is confirmed that Rh. mucilaginosa degrades the quorum sensing molecules via lactonase activity. To the best of our knowledge, this is the first documentation of the fact that Rh. mucilaginosa has activity against a broad range of AHLs namely C6-HSL, 3-oxo-C6-HSL and 3-hydroxy-C6-HSL.

  16. Rhodotorula Mucilaginosa, a Quorum Quenching Yeast Exhibiting Lactonase Activity Isolated from a Tropical Shoreline

    PubMed Central

    Ghani, Norshazliza Ab; Sulaiman, Joanita; Ismail, Zahidah; Chan, Xin-Yue; Yin, Wai-Fong; Chan, Kok-Gan

    2014-01-01

    Two microbial isolates from a Malaysian shoreline were found to be capable of degrading N-acylhomoserine lactones. Both Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry and 18S rDNA phylogenetic analyses confirmed that these isolates are Rhodotorula mucilaginosa. Quorum quenching activities were detected by a series of bioassays and rapid resolution liquid chromatography analysis. The isolates were able to degrade various quorum sensing molecules namely N-hexanoyl-L-homoserine lactone (C6-HSL), N-(3-oxo-hexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-L-homoserine lactone (3-hydroxy-C6-HSL). Using a relactonisation assay to verify the quorum quenching mechanism, it is confirmed that Rh. mucilaginosa degrades the quorum sensing molecules via lactonase activity. To the best of our knowledge, this is the first documentation of the fact that Rh. mucilaginosa has activity against a broad range of AHLs namely C6-HSL, 3-oxo-C6-HSL and 3-hydroxy-C6-HSL. PMID:24721765

  17. Saturation Mutagenesis of a CepR Binding Site as a Means to Identify New Quorum-regulated Promoters in Burkholderia cenocepacia

    PubMed Central

    Wei, Yuping; Ryan, Gina T.; Flores-Mireles, Ana L.; Costa, Esther D.; Schneider, David J.; Winans, Stephen C.

    2011-01-01

    Burkholderia cenocepacia is an opportunistic pathogen of humans that encodes two genes that resemble the acylhomoserine lactone (AHL) synthase gene luxI of Vibrio fischeri and three genes that resemble the AHL receptor gene luxR. Of these, CepI synthesizes octanoylhomoserine lactone (OHL), while CepR is an OHL-dependent transcription factor. In the current study we developed a strategy to identify genes that are directly regulated by CepR. We systematically altered a CepR binding site (cep box) upstream of a target promoter to identify nucleotides that are essential for CepR activity in vivo and for CepR binding in vitro. We constructed 34 self-complementary oligonucleotides containing altered cep boxes, and measured binding affinity for each. These experiments allowed us to identify a consensus CepR binding site. Several hundred similar sequences were identified, some of which were adjacent to probable promoters. Several such promoters were fused to a reporter gene with and without intact cep boxes. This allowed us to identify four new regulated promoters that were induced by OHL, and that required a cep box for induction. CepR-dependent, OHL-dependent expression of all four promoters was reconstituted in E. coli. Purified CepR bound to each of these sites in electrophoretic mobility shift assays. PMID:21255107

  18. First identification of three p-menthane lactones and their potential precursor, menthofuran, in red wines.

    PubMed

    Picard, Magali; de Revel, Gilles; Marchand, Stéphanie

    2017-02-15

    The p-menthane lactones constitute a family of powerful odorants, including the isomers of mintlactone and menthofurolactone that occur naturally in peppermint oil, known for their potent, mint-like olfactory properties. These lactones are closely related to the monoterpene-limonene secondary biotransformation and menthofuran has been identified as their common precursor in Mentha species. Using targeted GC-olfactometry and GC-MS analyses, together with quantification methods, we were able to demonstrate, for the first time, the presence of the diastereoisomers of these p-menthane lactones, as well as their common precursor, menthofuran, in red wines. In addition, we linked the presence of those lactones to interesting odorant zones, reminiscent of mint, detected in the studied wine. Although these p-menthane lactones may contribute individually to mint and coconut odors, sensory studies suggested for the first time that their combination at the levels found in the red wine studied resulted in a significant accentuation of freshness and mint notes.

  19. Sesquiterpene Lactones from Artemisia Genus: Biological Activities and Methods of Analysis

    PubMed Central

    Ivanescu, Bianca; Miron, Anca; Corciova, Andreia

    2015-01-01

    Sesquiterpene lactones are a large group of natural compounds, found primarily in plants of Asteraceae family, with over 5000 structures reported to date. Within this family, genus Artemisia is very well represented, having approximately 500 species characterized by the presence of eudesmanolides and guaianolides, especially highly oxygenated ones, and rarely of germacranolides. Sesquiterpene lactones exhibit a wide range of biological activities, such as antitumor, anti-inflammatory, analgesic, antiulcer, antibacterial, antifungal, antiviral, antiparasitic, and insect deterrent. Many of the biological activities are attributed to the α-methylene-γ-lactone group in their molecule which reacts through a Michael-addition with free sulfhydryl or amino groups in proteins and alkylates them. Due to the fact that most sesquiterpene lactones are thermolabile, less volatile compounds, they present no specific chromophores in the molecule and are sensitive to acidic and basic mediums, and their identification and quantification represent a difficult task for the analyst. Another problematic aspect is represented by the complexity of vegetal samples, which may contain compounds that can interfere with the analysis. Therefore, this paper proposes an overview of the methods used for the identification and quantification of sesquiterpene lactones found in Artemisia genus, as well as the optimal conditions for their extraction and separation. PMID:26495156

  20. In vitro analysis of the anthelmintic activity of forage chicory (Cichorium intybus L.) sesquiterpene lactones against a predominatly Haemonchus contortus egg population

    USDA-ARS?s Scientific Manuscript database

    The anthelmintic activity of chicory (Cichorium intybus L.) herbage has been attributed to sesquiterpene lactones. Chicory leaves contain significant amounts of lactucin (LAC), 8-deoxylactucin (DOL), and lactucopicrin (LPIC), but the proportions of these three sesquiterpene lactones vary among fora...

  1. Triazole-containing N-acyl homoserine lactones targeting the quorum sensing system in Pseudomonas aeruginosa.

    PubMed

    Hansen, Mette R; Jakobsen, Tim H; Bang, Claus G; Cohrt, Anders Emil; Hansen, Casper L; Clausen, Janie W; Le Quement, Sebastian T; Tolker-Nielsen, Tim; Givskov, Michael; Nielsen, Thomas E

    2015-04-01

    In an attempt to devise new antimicrobial treatments for biofilm infections, the bacterial cell-cell communication system termed quorum sensing has emerged as an attractive target. It has proven possible to intercept the communication system by synthetic non-native ligands and thereby lower the pathogenesis and antibiotic tolerance of a bacterial biofilm. To identify the structural elements important for antagonistic or agonistic activity against the Pseudomonas aeruginosa LasR protein, we report the synthesis and screening of new triazole-containing mimics of natural N-acyl homoserine lactones. A series of azide- and alkyne-containing homoserine lactone building blocks was used to prepare an expanded set of 123 homoserine lactone analogues through a combination of solution- and solid-phase synthesis methods. The resulting compounds were subjected to cell-based quorum sensing screening assays, thereby revealing several bioactive compounds, including 13 compounds with antagonistic activity and 9 compounds with agonistic activity.

  2. Macrocyclic lactones: A versatile source for omega radiohalogenated fatty acid analogs

    SciTech Connect

    Dougan, A.H.; Lyster, D.M.; Robertson, K.A.; Vincent, J.S.

    1984-01-01

    For each omega halogenated fatty acid there exists a potential omega hydroxy fatty acid and the corresponding macrocyclic lactone. The authors have utilized such lactones as starting materials for omega /sup 123/I fatty acid analogs intended for myocardial imaging. Macrocyclic musk lactones are industrially available; 120 analogs are described in the literature. The preparation requires saponification, tosylation, and radio-iodide substitution. Iodo-fatty acids are readily separated from tosylate fatty acids on TLC. While providing a secure source of 16-iodo-hexadecanoic acid and 17-iodo-heptadecanoic acid, the scheme allows ready access to a large number of untried fatty acid analogs. Examples presented are 16-iodo-hexadecanoic acid, 16-iodo-7-hexadecanoic acid, 16-iodo-12-oxa-hexadecanoic acid, 15-iodo-pentadecanoic acid, and 15-iodo-12-keto-pentadecanoic acid. Metabolic studies are in progress in mice and dogs to assess the utility of these analogs for myocardial imaging.

  3. Lipase-catalyzed ring-opening polymerization of lactones to polyesters and its mechanistic aspects.

    PubMed

    Namekawa, S; Suda, S; Uyama, H; Kobayashi, S

    1999-01-01

    Lipase catalysis induced a ring-opening polymerization of lactones with different ring-sizes. Small-size (four-membered) and medium-size lactones (six- and seven-membered) as well as macrolides (12-, 13-, 16-, and 17-membered) were subjected to lipase-catalyzed polymerization. The polymerization behaviors depended primarily on the lipase origin and the monomer structure. The macrolides showing much lower anionic polymerizability were enzymatically polymerized faster than epsilon-caprolactone. The granular immobilized lipase derived from Candida antartica showed extremely efficient catalysis in the polymerization of epsilon-caprolactone. Single-step terminal functionalization of the polyester was achieved by initiator and terminator methods. The enzymatic polymerizability of lactones was quantitatively evaluated by Michaelis-Menten kinetics.

  4. Dehydrocostus lactone enhances tumor necrosis factor-alpha-induced apoptosis of human leukemia HL-60 cells.

    PubMed

    Oh, G S; Pae, H O; Chung, H T; Kwon, J W; Lee, J H; Kwon, T O; Kwon, S Y; Chon, B H; Yun, Young Gab

    2004-05-01

    Sesquiterpene lactones have raised considerable interest because of their ability to block the activation of nuclear transcription factor-kappaB (NF-kappaB). NF-kappaB plays an important role in the resistance of cancer cells to the induction of apoptosis by anticancer drugs and tumor necrosis factor-alpha (TNF-alpha). Pharmacological inhibition of NF-kappaB offers the promise of enhancing the efficacy of anticancer therapies. Here, we demonstrate that dehydrocostus lactone (DL), the major sesquiterpene lactone isolated from the roots of Saussurea lappa, inhibits NF-kappaB activation by preventing TNF-alpha-induced degradation and phosphorylation of its inhibitory protein I-kappaB alpha in human leukemia HL-60 cells and that DL renders HL-60 cells susceptible to TNF-alpha-induced apoptosis by enhancing caspase-8 and caspase-3 activities.

  5. Catabolism of hydroxyacids and biotechnological production of lactones by Yarrowia lipolytica.

    PubMed

    Waché, Y; Aguedo, M; Nicaud, J-M; Belin, J-M

    2003-06-01

    The gamma- and delta-lactones of less than 12 carbons constitute a group of compounds of great interest to the flavour industry. It is possible to produce some of these lactones through biotechnology. For instance, gamma-decalactone can be obtained by biotransformation of methyl ricinoleate. Among the organisms used for this bioproduction, Yarrowia lipolytica is a yeast of choice. It is well adapted to growth on hydrophobic substrates, thanks to its efficient and numerous lipases, cytochrome P450, acyl-CoA oxidases and its ability to produce biosurfactants. Furthermore, genetic tools have been developed for its study. This review deals with the production of lactones by Y. lipolytica with special emphasis on the biotransformation of methyl ricinoleate to gamma-decalactone. When appropriate, information from the lipid metabolism of other yeast species is presented.

  6. Capillary zone electrophorsis for the analysis of naturally occurring 2-hydroxycitric acids and their lactones.

    PubMed

    Abhijith, B L; Mohan, Moolya; Joseph, David; Haleema, Simimole; Aboul-Enein, Hassan Y; Ibnusaud, Ibrahim

    2017-08-01

    A simple capillary zone electrophoresis method with direct ultraviolet detection has been developed for the analysis of naturally occurring diastereomeric 2-hydroxycitric acid lactones. Using 50 mM sodium phosphate buffer of pH 7, a baseline resolution Rs > 3.0 was observed for all organic acids selected for the present study. This method was employed for the quantitative determination of title acids present in the plant sources namely Garcinia cambogia fruit rinds and Hibiscus sabdariffa calyx. Conversion of 2-hydroxycitric acids to their lactones on heating the above plant sources is deliberated. The Hydrolysis of hydroxycitric acid lactones in aqueous solution is reported for the first time. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Lactone-ring-cleaving enzymes of microorganisms: their diversity and applications.

    PubMed

    Shimizu, S; Kataoka, M; Honda, K; Sakamoto, K

    2001-12-28

    Microbial lactonohydrolases (lactone-ring-cleaving enzymes) with unique characteristics were found. The Fusarium oxysporum enzyme catalyzes the reversible and stereospecific hydrolysis of aldonate lactones and D-pantolactone (D-PL), and is useful for the optical resolution of racemic PL. The Agrobacterium tumefaciens enzyme hydrolyzes several aromatic lactones, and catalyzes the stereospecific hydrolysis of PL like the Fusarium enzyme, but its selectivity is opposite. The Acinetobacter calcoaceticus enzyme catalyzing the specific hydrolysis of dihydrocoumarin belongs to serine-enzyme family, and is useful for enantioselective hydrolysis of methyl DL-beta-acetylthioisobutyrate and regioselective hydrolysis of methyl cetraxate. This enzyme also catalyzes the bromination of monochlorodimedon when incubated with H(2)O(2) and dihydrocoumarin.

  8. Thermoregulation of N-acyl homoserine lactone-based quorum sensing in the soft rot bacterium Pectobacterium atrosepticum.

    PubMed

    Latour, Xavier; Diallo, Stéphanie; Chevalier, Sylvie; Morin, Danièle; Smadja, Bruno; Burini, Jean-François; Haras, Dominique; Orange, Nicole

    2007-06-01

    The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level.

  9. Neocosmospora sp.-derived resorcylic acid lactones with in vitro binding capacity for human opioid and cannabinoid receptors

    USDA-ARS?s Scientific Manuscript database

    Bioassay-guided fractionation of a fungus Neocosmospora sp. (UM-031509) resulted in the isolation of three new resorcyclic acid lactones, neocosmosin A (2), neocosmosin B (3) and neocosmosin C (4). Three known resorcylic acid lactones, monocillin IV (1), monocillin II (5) and monorden (6) were also ...

  10. Preservation of the active lactone form of irinotecan using drug eluting beads for the treatment of colorectal cancer metastases.

    PubMed

    Tang, Yiqing; Czuczman, Peter R; Chung, Shui T; Lewis, Andrew L

    2008-04-07

    The distribution of the active lactone and the inactive carboxylate forms of irinotecan released from drug eluting beads composed of a sulfonate-modified PVA hydrogel was studied in order to ascertain the interaction between irinotecan, a water-soluble derivative of anti-cancer drug camptothecin, and the sulfonate groups in beads. Under a neutral condition of pH 7.0, it was demonstrated that the lactone form preferentially binds with sulfonate groups in the hydrogel beads through charge-charge interaction, and the equilibrium of the two forms shifts in favour of the lactone. In terms of stability, the drug-sulfonate interaction results in the retention of the active lactone form within the hydrogel beads. Kinetic experiments indicated that in PBS, the rate constants of lactone hydrolysis and carboxylate lactonization were 3.10 (+/-0.33)x10(-3) min(-1) and 1.36 (+/-0.04)x10(-3) min(-1), respectively. The modelling and elution experiments of the distribution of the lactone and carboxylate during irinotecan delivery by different methods, such as bolus injection, infusion and bead delivery, showed that both infusion and embolic bead delivery provided the lactone form with prolonged half-life. In addition, drug eluting beads have the characteristics of targeted delivery and low toxicity and the advantage of storage of the active form of irinotecan by polyanion stabilisation for use in local therapy of metastatic colorectal cancer to the liver.

  11. Quantification of several 4-alkyl substituted gamma-lactones in Australian wines.

    PubMed

    Cooke, Rachel C; Capone, Dimitra L; van Leeuwen, Katryna A; Elsey, Gordon M; Sefton, Mark A

    2009-01-28

    Stable isotope dilution assays have been developed for gamma-octalactone (1), gamma-nonalactone (2), gamma-decalactone (3) and gamma-dodecalactone (4) in both white and red wines for the first time. (2)H(7)-analogues of each lactone were prepared for use as internal standards via a strategy employing ring-opening, esterification and oxidation of the respective starting lactones. The methods were shown to be highly accurate and reproducible (R(2) > or = 0.999; SD < or = 1%). A large selection of Australian wines (n = 178) were analyzed for the presence of lactones 1-4. Fifty-eight white wines covering the varieties Chardonnay, Riesling, Sauvignon Blanc, Semillon and Viognier, as well as Botrytis style wines, were analyzed and showed broadly that gamma-octalactone (1) was the most common lactone, being observed above its limit of detection in 28 of the wines, followed by gamma-nonalactone (2) in 23 wines. The Botrytis style white wines had the highest concentrations of 1 and 2 (maximum concentrations 8.5 and 59 microg/L respectively). A total of 120 red wines covering the varieties Cabernet Sauvignon, Durif, Merlot, Pinot Noir and Shiraz were also studied and showed gamma-octalactone (1) and gamma-nonalactone (2) to be the most common lactones present, in 56 and 57 of the wines, respectively. gamma-Decalactone (3) was observed in only a small number (13) of red wine samples and not at all in the white varieties. gamma-Dodecalactone (4) was absent from all 178 samples studied. The highest concentrations of lactones 1, 2 and 3 in the red wines were 4.2, 39.7 and 4.0 microg/L respectively.

  12. Mechanistic studies of inactivation of glutathione S-transferase Pi isozyme by a haloenol lactone derivative.

    PubMed

    Zheng, Jiang; Liu, Guangxian; Tozkoparan, Birsen; Wen, Dingyi

    2005-03-01

    Cancer chemotherapy often fails due to acquired drug resistance. One of the most critical biochemical changes observed in drug-resistant tumor cells is over-expression of glutathione S-transferase Pi isozyme (GSTP1). Glutathione S-transferase inhibitors have been used as potentiating agents of chemotherapeutic drugs. Earlier we reported haloenol lactone 1 as a site-directed GSTP1 inactivator. We proposed that enzymatic hydrolysis of the haloenol lactone may be the initial step of GSTP1 chemical modification, resulting in the inactivation of the enzyme. Enzyme inactivation is initiated through addition of Cys-47 to the lactone ring, which is opened in the process to form an alpha-bromoketone adduct. The acidity of Cys-47 confers good leaving group properties, and rapid hydrolysis occurs to generate an alpha-bromoketoacid intermediate. The reaction may proceed via alkylation of the transient thioester to form a six-membered ring episulfonium ion intermediate which would be yet more reactive toward hydrolysis, with either process leading to the observed mass increase of 230 Da. To probe the importance of the bromine of the lactone in GST inactivation, we designed and synthesized compound 2. Unlike lactone 1, lactone 2 did not show time-dependent inhibitory effect on GSTP1. Incubation of compounds 1 and 2 with excess of N-acetyl cysteine produced the corresponding di-N-acetyl cysteine conjugate and mono-N-acetyl cysteine conjugate, respectively. To probe the role of Cys-47 in the inactivation of GSTP1 by compound 1, we prepared mutant C47A GSTP1. The mutant GSTP1 still showed good activity toward CDNB, but it lost susceptibility to the inactivation by compound 1. In addition, LC-MS/MS technique allowed us to identify the modified Cys-47 after the enzyme was exposed to compound 1.

  13. Synthesis and Antifeedant Activity of Racemic and Optically Active Hydroxy Lactones with the p-Menthane System

    PubMed Central

    Grudniewska, Aleksandra; Kłobucki, Marek; Dancewicz, Katarzyna; Szczepanik, Maryla; Gabryś, Beata; Wawrzeńczyk, Czesław

    2015-01-01

    Two racemic and two enantiomeric pairs of new δ-hydroxy-γ-lactones based on the p-menthane system were prepared from racemic and optically active cis- and trans-piperitols. The Johnson-Claisen rearrangement of the piperitols, epoxidation of the γδ-unsaturated esters, and acidic lactonization of the epoxy esters were described. The structures of the compounds were confirmed spectroscopically. The antifeedant activities of the hydroxy lactones and racemic piperitone were evaluated against three insect pests: lesser mealworm, Alphitobius diaperinus (Panzer); Colorado potato beetle, Leptinotarsa decemlineata (Say); and peach-potato aphid, Myzus persicae (Sulz.). The chemical transformation of piperitone by the introduction of a lactone moiety and a hydroxy group changed its antifeedant properties. Behavioral bioassays showed that the feeding deterrent activity depended on the insect species and the structure of the compounds. All hydroxy lactones deterred the settling of M. persicae. Among chewing insects, the highest sensitivity showed A. diaperinus adults. PMID:26132506

  14. Activation of antioxidant response element in mouse primary cortical cultures with sesquiterpene lactones isolated from Tanacetum parthenium

    PubMed Central

    Fischedick, Justin T; Standiford, Miranda; Johnson, Delinda A.; De Vos, Ric C.H.; Todorović, Slađana; Banjanac, Tijana; Verpoorte, Rob; Johnson, Jeffrey A.

    2012-01-01

    Tanacetum parthenium (Asteraceae) produces biologically active sesquiterpene lactones (SL). Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor known to activate a series of genes termed the antioxidant response element (ARE). Activation of the Nrf2/ARE may be useful for the treatment of neurodegenerative disease. In this study we isolated 11 sesquiterpene lactones from T. parthenium with centrifugal partition chromatography and semi-preparative HPLC. Compounds were screened in-vitro for their ability to activate the ARE on primary mouse cortical cultures as well as for their toxicity towards the cultures. All sesquiterpene lactones containing the α-methylene-γ-lactone moiety were able to activate the ARE although a number of compounds displayed significant cellular toxicity towards the cultures. The structure activity relationship of the sesquiterpene lactones indicate that the guaianolides isolated were more active and less toxic then the germacranolides. PMID:22923197

  15. Synthesis and Antifeedant Activity of Racemic and Optically Active Hydroxy Lactones with the p-Menthane System.

    PubMed

    Grudniewska, Aleksandra; Kłobucki, Marek; Dancewicz, Katarzyna; Szczepanik, Maryla; Gabryś, Beata; Wawrzeńczyk, Czesław

    2015-01-01

    Two racemic and two enantiomeric pairs of new δ-hydroxy-γ-lactones based on the p-menthane system were prepared from racemic and optically active cis- and trans-piperitols. The Johnson-Claisen rearrangement of the piperitols, epoxidation of the γδ-unsaturated esters, and acidic lactonization of the epoxy esters were described. The structures of the compounds were confirmed spectroscopically. The antifeedant activities of the hydroxy lactones and racemic piperitone were evaluated against three insect pests: lesser mealworm, Alphitobius diaperinus (Panzer); Colorado potato beetle, Leptinotarsa decemlineata (Say); and peach-potato aphid, Myzus persicae (Sulz.). The chemical transformation of piperitone by the introduction of a lactone moiety and a hydroxy group changed its antifeedant properties. Behavioral bioassays showed that the feeding deterrent activity depended on the insect species and the structure of the compounds. All hydroxy lactones deterred the settling of M. persicae. Among chewing insects, the highest sensitivity showed A. diaperinus adults.

  16. Antibacterial and cytotoxic activities of the sesquiterpene lactones cnicin and onopordopicrin.

    PubMed

    Bach, Sandra M; Fortuna, Mario A; Attarian, Rodgoun; de Trimarco, Juliana T; Catalán, César A N; Av-Gay, Yossef; Bach, Horacio

    2011-02-01

    The antimicrobial and cytotoxic activities of chloroform extracts from the weeds Centaurea tweediei and C. diffusa, and the main sesquiterpene lactones isolated from these species, onopordopicrin and cnicin, respectively, were assayed. Results show that the chloroform extracts from both Centaurea species possess antibacterial activities against a panel of Gram-positive and Gram-negative bacteria. Remarkable antibacterial activity against methicillin-resistant Staphylococcus aureus was also measured. Both the extracts and the purified sesquiterpene lactones show high cytotoxicity against human-derived macrophages. Despite this cytotoxicity, C. diffusa chloroform extract and cnicin are attractive candidates for evaluation as antibiotics in topical preparations against skin-associated pathogens.

  17. Samarium(II) promoted stereoselective synthesis of antiproliferative cis-beta-alkoxy-gamma-alkyl-gamma-lactones.

    PubMed

    Donadel, Osvaldo J; Martín, Tomás; Martín, Víctor S; Padrón, José M

    2007-01-01

    Samarium(II) iodide promotes the stereoselective synthesis of cis-beta-alkoxy-gamma-alkyl-gamma-lactones under mild conditions starting from linear precursors. The in vitro antiproliferative activities were examined in the human solid tumor cell lines from diverse origin A2780, SW1573, and WiDr. From the growth inhibition data a structure-activity relationship was obtained. Overall the results point to the relevant role of cis-beta-alkoxy-gamma-alkyl-gamma-lactones as novel scaffolds for the development of new anticancer drugs.

  18. (1)H chemical shift differences of Prelog-Djerassi lactone derivatives: DFT and NMR conformational studies.

    PubMed

    Aímola, Túlio J; Lima, Dimas J P; Dias, Luiz C; Tormena, Cláudio F; Ferreira, Marco A B

    2015-02-21

    This work reports an experimental and theoretical study of the conformational preferences of several Prelog-Djerassi lactone derivatives, to elucidate the (1)H NMR chemical shift differences in the lactonic core that are associated with the relative stereochemistry of these derivatives. The boat-like conformation of explains the anomalous (1)H chemical shift between H-5a and H-5b, in which the two methyl groups (C-8 and C-9) face H-5b, leading to its higher shielding effect.

  19. Short Flow-Photochemistry Enabled Synthesis of the Cytotoxic Lactone (+)-Goniofufurone.

    PubMed

    Ralph, Michael; Ng, Sean; Booker-Milburn, Kevin I

    2016-03-04

    A photochemical approach to the cytotoxic lactone (+)-goniofufurone (1) is reported. Paternò-Büchi [2 + 2] photocycloaddition from known enol ether 4, derived from the readily available sugar d-isosorbide, yielded oxetane 7. This slow, dilute reaction was scaled up by using flow photochemistry to yield >40 g of 7. Installation of the key lactone ring was achieved via a unique Wacker-style oxidation of an enol-ether bond. Acid-catalyzed aqueous ring opening provided 1 in five steps from 4 (11.5% overall).

  20. [Effects of ginkgo diterpene lactones meglumine injection's activated carbon adsorption technology on officinal components].

    PubMed

    Zhou, En-li; Wang, Ren-jie; Li, Miao; Wang, Wei; Xu, Dian-hong; Hu, Yang; Wang, Zhen-zhong; Bi, Yu-an; Xiao, Wei

    2015-10-01

    With the diversion rate of ginkgolide A, B, K as comprehensive evaluation indexes, the amount of activated carbon, ad- sorption time, mix rate, and adsorption temperature were selected as factors, orthogonal design which based on the evaluation method of information entropy was used to optimize activated carbon adsorption technology of ginkgo diterpene lactones meglumine injection. Opti- mized adsorption conditions were as follows: adsorbed 30 min with 0.2% activated carbon in 25 °C, 40 r ·min⁻¹, validation test re- sult display. The optimum extraction condition was stable and feasible, it will provide a basis for ginkgo diterpene lactone meglumine injection' activated carbon adsorption process.

  1. Purification and identification of antimicrobial sesquiterpene lactones from yacon (Smallanthus sonchifolius) leaves.

    PubMed

    Lin, Fengqiu; Hasegawa, Morifumi; Kodama, Osamu

    2003-10-01

    The extraction of yacon [Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson; Asteraceae] leaves and chromatographic separation yielded two new antibacterial melampolide-type sesquiterpene lactones, 8beta-tigloyloxymelampolid-14-oic acid methyl ester and 8beta-methacryloyloxymelampolid-14-oic acid methyl ester, as well as the four known melampolides, sonchifolin, uvedalin, enhydrin and fluctuanin. The newly identified compound, 8beta-methacryloyloxymelampolid-14-oic acid methyl ester, exhibited potent antimicrobial activity against Bacillus subtilis and Pyricularia oryzae, while 8beta-tigloyloxymelampolid-14-oic acid methyl ester showed lower activity. Fluctuanin exhibited the strongest antibacterial activity against B. subtilis among these six sesquiterpene lactones.

  2. Gamma-lactone-Functionalized antitumoral acetogenins are the most potent inhibitors of mitochondrial complex I.

    PubMed

    Tormo, J R; Estornell, E; Gallardo, T; González, M C; Cavé, A; Granell, S; Cortes, D; Zafra-Polo, M C

    2001-03-12

    To study the relevance of the terminal alpha,beta-unsaturated gamma-methyl-gamma-lactone moiety of the antitumoral acetogenins of Annonaceae for potent mitochondrial complex I inhibition, we have prepared a series of semisynthetic acetogenins with modifications only in this part of the molecule, from the natural rolliniastatin-1 (1) and cherimolin-1 (2). Some of the hydroxylated derivatives (1b, 1d and 1e) in addition to two infrequent natural beta-hydroxy gamma-methyl gamma-lactone acetogenins, laherradurin (3) and itrabin (4), are more potent complex I inhibitors than any other known compounds.

  3. Anticancer activities of sesquiterpene lactones from Cyathocline purpurea in vitro.

    PubMed

    Ma, Guoyi; Chong, Li; Li, Zuqiang; Cheung, Andrew H T; Tattersall, Martin H N

    2009-06-01

    L1210 cells could be related to alkylation of the sulfhydryl enzymes involved in nucleic acids and protein synthesis, as previously found for other sesquiterpenes with the alpha-methylene-gamma-lactone moiety present in santamarine, 9beta-acetoxycostunolide and 9beta-acetoxyparthenolide. It may also be related to suppression of microtubular proteins. Santamarine and 9beta-acetoxycostunolide induced apoptosis of L1210 cells via activation of caspase 3.

  4. 1,3-Dipolar cycloaddition of a cyclic nitrone derived from 2-deoxy-D-ribose to α,β-unsaturated lactones: An entry to carbapenem antibiotics.

    PubMed

    Pieczykolan, Michał; Staszewska-Krajewska, Olga; Furman, Bartłomiej; Chmielewski, Marek

    2016-10-04

    1,3-Dipolar cycloadditions of 2-deoxy-D-ribose-derived L-threo five-membered cyclic nitrone to α,β-unsaturated γ- and δ-lactones were investigated. Cycloadducts obtained from δ-lactones, after NO bond cleavage, opening of the lactone ring, and protection of hydroxyl groups were subjected to β-lactam ring formation by using Mukaiyama's salt. Cycloadducts from γ-lactones subjected to the same reaction sequence undergo β-elimination of a water molecule to provide pyrrolidine-substituted unsaturated γ-lactones. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Developmental and Environmental Effects on Sesquiterpene Lactones in Cultivated Arnica montana L.

    PubMed

    Todorova, Milka; Trendafilova, Antoaneta; Vitkova, Antonina; Petrova, Maria; Zayova, Ely; Antonova, Daniela

    2016-08-01

    The amount of sesquiterpene lactones and the lactone profile of Arnica montana L. in flowering and seed formation stages in vitro and in vivo propagated from seeds of German, Ukrainian, and Austrian origin and grown in two experimental fields were studied. It was found that in vitro propagated 2-year plants in full flowering stage accumulated higher amount of lactones in comparison to in vivo propagated 3-year plants and to the seed formation stage, respectively. Helenalins predominated in in vivo propagated 2-year or in vitro propagated 3-year plants. 2-Methylbutyrate (2MeBu) was the principal ester in the samples with prevalence of helenalins, while isobutyrate (iBu) was the major one in the samples with predominance of 11,13-dihydrohele