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‣ Cell-cell signal-dependent dynamic interactions between HD-GYP and GGDEF domain proteins mediate virulence in Xanthomonas campestris

RYAN, Robert P.; MCCARTHY, Yvonne; ANDRADE, Maxuel; FARAH, Chuck S.; ARMITAGE, Judith P.; DOW, J. Maxwell
Fonte: NATL ACAD SCIENCES Publicador: NATL ACAD SCIENCES
Tipo: Artigo de Revista Científica
Português
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RpfG is a paradigm for a class of widespread bacterial two-component regulators with a CheY-like receiver domain attached to a histidine-aspartic acid-glycine-tyrosine-proline (HD-GYP) cyclic di-GMP phosphodiesterase domain. In the plant pathogen Xanthomonas campestris pv. campestris (Xcc), a two-component system comprising RpfG and the complex sensor kinase RpfC is implicated in sensing and responding to the diffusible signaling factor (DSF), which is essential for cell-cell signaling. RpfF is involved in synthesizing DSF, and mutations of rpfF, rpfG, or rpfC lead to a coordinate reduction in the synthesis of virulence factors such as extracellular enzymes, biofilm structure, and motility. Using yeast two-hybrid analysis and fluorescence resonance energy transfer experiments in Xcc, we show that the physical interaction of RpfG with two proteins with diguanylate cyclase (GGDEF) domains controls a subset of RpfG-regulated virulence functions. RpfG interactions were abolished by alanine substitutions of the three residues of the conserved GYP motif in the HD-GYP domain. Changing the GYP motif or deletion of the two GGDEF-domain proteins reduced Xcc motility but not the synthesis of extracellular enzymes or biofilm formation. RpfG-GGDEF interactions are dynamic and depend on DSF signaling...

‣ Characterization of a Diffusible Signal Capable of Inducing Defense Gene Expression in Tobacco.

Chappell, J.; Levine, A.; Tenhaken, R.; Lusso, M.; Lamb, C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1997 Português
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Treatment of tobacco (Nicotiana tabacum) cell-suspension cultures with cryptogein, an elicitin protein from Phytophthora cryptogea, resulted in the release of a factor(s) that diffused through a 1000-D cutoff dialysis membrane and was capable of inducing sesquiterpene cyclase enzyme activity (a key phytoalexin biosynthetic enzyme in solanaceous plants) when added to fresh cell-suspension cultures. The diffusible factor(s) was released from cells over a 20-h period and induced a more rapid induction of cyclase enzyme activity than did direct treatment of the cultures with pure elicitin protein. The diffusible factor also induced a more rapid accumulation of transcripts encoding for sesquiterpene cyclase, acidic and basic chitinase, and hsr203 (a putative hypersensitive response gene) than did elicitin treatment. The diffusible factor(s) was resistant to protease, pectinase, Dnase, and RNase treatments, was not extractable into organic solvents, and was not immunoprecipitable when challenged with polyclonal antibodies prepared against elicitin protein. The diffusible factor(s) could not induce the release of more factor, suggesting that it was a terminal signal. These results are consistent with the notion that cells directly challenged or stimulated by pathogen-derived elicitors release diffusible secondary signal molecules that orchestrate the induction of complementary defense responses in neighboring cells.

‣ Cell–cell signaling in Xanthomonas campestris involves an HD-GYP domain protein that functions in cyclic di-GMP turnover

Ryan, Robert P.; Fouhy, Yvonne; Lucey, Jean F.; Crossman, Lisa C.; Spiro, Stephen; He, Ya-Wen; Zhang, Lian-Hui; Heeb, Stephan; Cámara, Miguel; Williams, Paul; Dow, J. Maxwell
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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HD-GYP is a protein domain of unknown biochemical function implicated in bacterial signaling and regulation. In the plant pathogen Xanthomonas campestris pv. campestris, the synthesis of virulence factors and dispersal of biofilms are positively controlled by a two-component signal transduction system comprising the HD-GYP domain regulatory protein RpfG and cognate sensor RpfC and by cell–cell signaling mediated by the diffusible signal molecule DSF (diffusible signal factor). The RpfG/RpfC two-component system has been implicated in DSF perception and signal transduction. Here we show that the role of RpfG is to degrade the unusual nucleotide cyclic di-GMP, an activity associated with the HD-GYP domain. Mutation of the conserved H and D residues of the isolated HD-GYP domain resulted in loss of both the enzymatic activity against cyclic di-GMP and the regulatory activity in virulence factor synthesis. Two other protein domains, GGDEF and EAL, are already implicated in the synthesis and degradation respectively of cyclic di-GMP. As with GGDEF and EAL domains, the HD-GYP domain is widely distributed in free-living bacteria and occurs in plant and animal pathogens, as well as beneficial symbionts and organisms associated with a range of environmental niches. Identification of the role of the HD-GYP domain thus increases our understanding of a signaling network whose importance to the lifestyle of diverse bacteria is now emerging.

‣ Diffusible Signal Factor-Dependent Cell-Cell Signaling and Virulence in the Nosocomial Pathogen Stenotrophomonas maltophilia▿

Fouhy, Yvonne; Scanlon, Karl; Schouest, Katherine; Spillane, Charles; Crossman, Lisa; Avison, Matthew B.; Ryan, Robert P.; Dow, J. Maxwell
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
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The genome of Stenotrophomonas maltophilia encodes a cell-cell signaling system that is highly related to the diffusible signal factor (DSF)-dependent system of the phytopathogen Xanthomonas campestris. Here we show that in S. maltophilia, DSF signaling controls factors contributing to the virulence and antibiotic resistance of this important nosocomial pathogen.

‣ Controlled synthesis of the DSF cell–cell signal is required for biofilm formation and virulence in Xanthomonas campestris

Torres, Pablo S; Malamud, Florencia; Rigano, Luciano A; Russo, Daniela M; Marano, María Rosa; Castagnaro, Atilio P; Zorreguieta, Angeles; Bouarab, Kamal; Dow, John Maxwell; Vojnov, Adrián A
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Publicado em /08/2007 Português
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Virulence of the black rot pathogen Xanthomonas campestris pv. campestris (Xcc) is regulated by cell–cell signalling involving the diffusible signal factor DSF. Synthesis and perception of DSF require products of genes within the rpf cluster (for regulation of pathogenicity factors). RpfF directs DSF synthesis whereas RpfC and RpfG are involved in DSF perception. Here we have examined the role of the rpf/DSF system in biofilm formation in minimal medium using confocal laser-scanning microscopy of GFP-labelled bacteria. Wild-type Xcc formed microcolonies that developed into a structured biofilm. In contrast, an rpfF mutant (DSF-minus) and an rpfC mutant (DSF overproducer) formed only unstructured arrangements of bacteria. A gumB mutant, defective in xanthan biosynthesis, was also unable to develop the typical wild-type biofilm. Mixed cultures of gumB and rpfF mutants formed a typical biofilm in vitro. In contrast, in mixed cultures the rpfC mutant prevented the formation of the structured biofilm by the wild-type and did not restore wild-type biofilm phenotypes to gumB or rpfF mutants. These effects on structured biofilm formation were correlated with growth and disease development by Xcc strains in Nicotiana benthamiana leaves. These findings suggest that DSF signalling is finely balanced during both biofilm formation and virulence.

‣ Xanthomonas campestris Overcomes Arabidopsis Stomatal Innate Immunity through a DSF Cell-to-Cell Signal-Regulated Virulence Factor1[OA]

Gudesblat, Gustavo E.; Torres, Pablo S.; Vojnov, Adrián A.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /02/2009 Português
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Pathogen-induced stomatal closure is part of the plant innate immune response. Phytopathogens using stomata as a way of entry into the leaf must avoid the stomatal response of the host. In this article, we describe a factor secreted by the bacterial phytopathogen Xanthomonas campestris pv campestris (Xcc) capable of interfering with stomatal closure induced by bacteria or abscisic acid (ABA). We found that living Xcc, as well as ethyl acetate extracts from Xcc culture supernatants, are capable of reverting stomatal closure induced by bacteria, lipopolysaccharide, or ABA. Xcc ethyl acetate extracts also complemented the infectivity of Pseudomonas syringae pv tomato (Pst) mutants deficient in the production of the coronatine toxin, which is required to overcome stomatal defense. By contrast, the rpfF and rpfC mutant strains of Xcc, which are unable to respectively synthesize or perceive a diffusible molecule involved in bacterial cell-to-cell signaling, were incapable of reverting stomatal closure, indicating that suppression of stomatal response by Xcc requires an intact rpf/diffusible signal factor system. In addition, we found that guard cell-specific Arabidopsis (Arabidopsis thaliana) Mitogen-Activated Protein Kinase3 (MPK3) antisense mutants were unresponsive to bacteria or lipopolysaccharide in promotion of stomatal closure...

‣ Intraspecies Signaling Involving the Diffusible Signal Factor BDSF (cis-2-Dodecenoic Acid) Influences Virulence in Burkholderia cenocepacia▿ §

Ryan, Robert P.; McCarthy, Yvonne; Watt, Steven A.; Niehaus, Karsten; Dow, J. Maxwell
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Burkholderia cenocepacia produces a diffusible fatty acid signal molecule, cis-2-dodecenoic acid (BDSF), that has been implicated in interspecies and interkingdom communication. Here, we show that BDSF also acts as an intraspecies signal in B. cenocepacia to control factors contributing to virulence of this major opportunistic pathogen.

‣ The Cyclic Nucleotide Monophosphate Domain of Xanthomonas campestris Global Regulator Clp Defines a New Class of Cyclic Di-GMP Effectors ▿ † ‡

Tao, Fei; He, Ya-Wen; Wu, Dong-Hui; Swarup, Sanjay; Zhang, Lian-Hui
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
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The widely conserved second messenger cyclic diguanosine monophosphate (c-di-GMP) plays a key role in quorum-sensing (QS)-dependent production of virulence factors in Xanthomonas campestris pv. campestris. The detection of QS diffusible signal factor (DSF) by the sensor RpfC leads to the activation of response regulator RpfG, which activates virulence gene expression by degrading c-di-GMP. Here, we show that a global regulator in the X. campestris pv. campestris QS regulatory pathway, Clp, is a c-di-GMP effector. c-di-GMP specifically binds to Clp with high affinity and induces allosteric conformational changes that abolish the interaction between Clp and its target gene promoter. Clp is similar to the cyclic AMP (cAMP) binding proteins Crp and Vfr and contains a conserved cyclic nucleotide monophosphate (cNMP) binding domain. Using site-directed mutagenesis, we found that the cNMP binding domain of Clp contains a glutamic acid residue (E99) that is essential for c-di-GMP binding. Substituting the residue with serine (E99S) resulted in decreased sensitivity to changes in the intracellular c-di-GMP level and attenuated bacterial virulence. These data establish the direct role of Clp in the response to fluctuating c-di-GMP levels and depict a novel mechanism by which QS links the second messenger with the X. campestris pv. campestris virulence regulon.

‣ Cis-2-dodecenoic acid receptor RpfR links quorum-sensing signal perception with regulation of virulence through cyclic dimeric guanosine monophosphate turnover

Deng, Yinyue; Schmid, Nadine; Wang, Chao; Wang, Jianhe; Pessi, Gabriella; Wu, Donghui; Lee, Jasmine; Aguilar, Claudio; Ahrens, Christian H.; Chang, Changqing; Song, Haiwei; Eberl, Leo; Zhang, Lian-Hui
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
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Many bacterial pathogens produce diffusible signal factor (DSF)-type quorum sensing (QS) signals in modulation of virulence and biofilm formation. Previous work on Xanthomonas campestris showed that the RpfC/RpfG two-component system is involved in sensing and responding to DSF signals, but little is known in other microorganisms. Here we show that in Burkholderia cenocepacia the DSF-family signal cis-2-dodecenoic acid (BDSF) negatively controls the intracellular cyclic dimeric guanosine monophosphate (c-di-GMP) level through a receptor protein RpfR, which contains Per/Arnt/Sim (PAS)-GGDEF-EAL domains. RpfR regulates the same phenotypes as BDSF including swarming motility, biofilm formation, and virulence. In addition, the BDSF− mutant phenotypes could be rescued by in trans expression of RpfR, or its EAL domain that functions as a c-di-GMP phosphodiesterase. BDSF is shown to bind to the PAS domain of RpfR with high affinity and stimulates its phosphodiesterase activity through induction of allosteric conformational changes. Our work presents a unique and widely conserved DSF-family signal receptor that directly links the signal perception to c-di-GMP turnover in regulation of bacterial physiology.

‣ 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

Udine, Claudia; Brackman, Gilles; Bazzini, Silvia; Buroni, Silvia; Van Acker, Heleen; Pasca, Maria Rosalia; Riccardi, Giovanna; Coenye, Tom
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 28/01/2013 Português
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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...

‣ Phenotype Overlap in Xylella fastidiosa Is Controlled by the Cyclic Di-GMP Phosphodiesterase Eal in Response to Antibiotic Exposure and Diffusible Signal Factor-Mediated Cell-Cell Signaling

de Souza, Alessandra A.; Ionescu, Michael; Baccari, Clelia; da Silva, Aline M.; Lindow, Steven E.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2013 Português
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Eal is an EAL domain protein in Xylella fastidiosa homologous to one involved in resistance to tobramycin in Pseudomonas aeruginosa. EAL and HD-GYP domain proteins are implicated in the hydrolysis of the secondary messenger bis-(3′-5′)-cyclic dimeric GMP (cyclic di-GMP). Cell density-dependent communication mediated by a Diffusible Signal Factor (DSF) also modulates cyclic di-GMP levels in X. fastidiosa, thereby controlling the expression of virulence genes and genes involved in insect transmission. The possible linkage of Eal to both extrinsic factors such as antibiotics and intrinsic factors such as quorum sensing, and whether both affect virulence, was thus addressed. Expression of eal was induced by subinhibitory concentrations of tobramycin, and an eal deletion mutant was more susceptible to this antibiotic than the wild-type strain and exhibited phenotypes similar to those of an rpfF deletion mutant blocked in DSF production, such as hypermotility, reduced biofilm formation, and hypervirulence to grape. Consistent with that, the rpfF mutant was more susceptible than the wild-type strain to tobramycin. Therefore, we propose that cell-cell communication and antibiotic stress can apparently lead to similar modulations of cyclic di-GMP in X. fastidiosa...

‣ Diffusible Signal Factor (DSF) Synthase RpfF of Xylella fastidiosa Is a Multifunction Protein Also Required for Response to DSF

Ionescu, Michael; Baccari, Clelia; Da Silva, Aline Maria; Garcia, Angelica; Yokota, Kenji; Lindow, Steven E.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2013 Português
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Xylella fastidiosa, like related Xanthomonas species, employs an Rpf cell-cell communication system consisting of a diffusible signal factor (DSF) synthase, RpfF, and a DSF sensor, RpfC, to coordinate expression of virulence genes. While phenotypes of a ΔrpfF strain in Xanthomonas campestris could be complemented by its own DSF, the DSF produced by X. fastidiosa (XfDSF) did not restore expression of the XfDSF-dependent genes hxfA and hxfB to a ΔrpfF strain of X. fastidiosa, suggesting that RpfF is involved in XfDSF sensing or XfDSF-dependent signaling. To test this conjecture, rpfC and rpfF of X. campestris were replaced by those of X. fastidiosa, and the contribution of each gene to the induction of a X. campestris DSF-dependent gene was assessed. As in X. fastidiosa, XfDSF-dependent signaling required both X. fastidiosa proteins RpfF and RpfC. RpfF repressed RpfC signaling activity, which in turn was derepressed by XfDSF. A mutated X. fastidiosa RpfF protein with two substitutions of glutamate to alanine in its active site was incapable of XfDSF production yet enabled a response to XfDSF, indicating that XfDSF production and the response to XfDSF are two separate functions in which RpfF is involved. This mutant was also hypervirulent to grape...

‣ Two Different rpf Clusters Distributed among a Population of Stenotrophomonas maltophilia Clinical Strains Display Differential Diffusible Signal Factor Production and Virulence Regulation

Huedo, Pol; Yero, Daniel; Martínez-Servat, Sònia; Estibariz, Iratxe; Planell, Raquel; Martínez, Paula; Ruyra, Àngels; Roher, Nerea; Roca, Ignasi; Vila, Jordi; Daura, Xavier; Gibert, Isidre
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/2014 Português
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The quorum-sensing (QS) system present in the emerging nosocomial pathogen Stenotrophomonas maltophilia is based on the signaling molecule diffusible signal factor (DSF). Production and detection of DSF are governed by the rpf cluster, which encodes the synthase RpfF and the sensor RpfC, among other components. Despite a well-studied system, little is known about its implication in virulence regulation in S. maltophilia. Here, we have analyzed the rpfF gene from 82 S. maltophilia clinical isolates. Although rpfF was found to be present in all of the strains, it showed substantial variation, with two populations (rpfF-1 and rpfF-2) clearly distinguishable by the N-terminal region of the protein. Analysis of rpfC in seven complete genome sequences revealed a corresponding variability in the N-terminal transmembrane domain of its product, suggesting that each RpfF variant has an associated RpfC variant. We show that only RpfC–RpfF-1 variant strains display detectable DSF production. Heterologous rpfF complementation of ΔrpfF mutants of a representative strain of each variant suggests that RpfF-2 is, however, functional and that the observed DSF-deficient phenotype of RpfC–RpfF-2 variant strains is due to permanent repression of RpfF-2 by RpfC-2. This is corroborated by the ΔrpfC mutant of the RpfC–RpfF-2 representative strain. In line with this observations...

‣ The PAS domain‐containing histidine kinase RpfS is a second sensor for the diffusible signal factor of Xanthomonas campestris

An, Shi‐Qi; Allan, John H.; McCarthy, Yvonne; Febrer, Melanie; Dow, J. Maxwell; Ryan, Robert P.
Fonte: Blackwell Scientific Publications Publicador: Blackwell Scientific Publications
Tipo: Artigo de Revista Científica
Português
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A cell–cell signalling system mediated by the fatty acid signal DSF controls the virulence of Xanthomonas campestris pv. campestris (Xcc) to plants. The synthesis and recognition of the DSF signal depends upon different Rpf proteins. DSF signal generation requires RpfF whereas signal perception and transduction depends upon the sensor RpfC and regulator RpfG. Detailed analyses of the regulatory roles of different Rpf proteins have suggested the occurrence of further sensors for DSF. Here we have used a mutagenesis approach coupled with high‐resolution transcriptional analysis to identify XC_2579 (RpfS) as a second sensor for DSF in Xcc. RpfS is a complex sensor kinase predicted to have multiple Per/Arnt/Sim (PAS) domains, a histidine kinase domain and a C‐terminal receiver (REC) domain. Isothermal calorimetry showed that DSF bound to the isolated N‐terminal PAS domain with a Kd of 1.4 μM. RpfS controlled expression of a sub‐set of genes distinct from those controlled by RpfC to include genes involved in type IV secretion and chemotaxis. Mutation of XC_2579 was associated with a reduction in virulence of Xcc to Chinese Radish when assayed by leaf spraying but not by leaf inoculation, suggesting a role for RpfS‐controlled factors in the epiphytic phase of the disease cycle.

‣ The DSF Family of Cell–Cell Signals: An Expanding Class of Bacterial Virulence Regulators

Ryan, Robert P.; An, Shi-qi; Allan, John H.; McCarthy, Yvonne; Dow, J. Maxwell
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 16/07/2015 Português
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Many pathogenic bacteria use cell–cell signaling systems involving the synthesis and perception of diffusible signal molecules to control virulence as a response to cell density or confinement to niches. Bacteria produce signals of diverse structural classes. Signal molecules of the diffusible signal factor (DSF) family are cis-2-unsaturated fatty acids. The paradigm is cis-11-methyl-2-dodecenoic acid from Xanthomonas campestris pv. campestris (Xcc), which controls virulence in this plant pathogen. Although DSF synthesis was thought to be restricted to the xanthomonads, it is now known that structurally related molecules are produced by the unrelated bacteria Burkholderia cenocepacia and Pseudomonas aeruginosa. Furthermore, signaling involving these DSF family members contributes to bacterial virulence, formation of biofilms and antibiotic tolerance in these important human pathogens. Here we review the recent advances in understanding DSF signaling and its regulatory role in different bacteria. These advances include the description of the pathway/mechanism of DSF biosynthesis, identification of novel DSF synthases and new members of the DSF family, the demonstration of a diversity of DSF sensors to include proteins with a Per-Arnt-Sim (PAS) domain and the description of some of the signal transduction mechanisms that impinge on virulence factor expression. In addition...

‣ Iron is a signal for Stenotrophomonas maltophilia biofilm formation, oxidative stress response, OMPs expression, and virulence

García, Carlos A.; Alcaraz, Eliana S.; Franco, Mirta A.; Passerini de Rossi, Beatriz N.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 04/09/2015 Português
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Stenotrophomonas maltophilia is an emerging nosocomial pathogen. In many bacteria iron availability regulates, through the Fur system, not only iron homeostasis but also virulence. The aim of this work was to assess the role of iron on S. maltophilia biofilm formation, EPS production, oxidative stress response, OMPs regulation, quorum sensing (QS), and virulence. Studies were done on K279a and its isogenic fur mutant F60 cultured in the presence or absence of dipyridyl. This is the first report of spontaneous fur mutants obtained in S. maltophilia. F60 produced higher amounts of biofilms than K279a and CLSM analysis demonstrated improved adherence and biofilm organization. Under iron restricted conditions, K279a produced biofilms with more biomass and enhanced thickness. In addition, F60 produced higher amounts of EPS than K279a but with a similar composition, as revealed by ATR-FTIR spectroscopy. With respect to the oxidative stress response, MnSOD was the only SOD isoenzyme detected in K279a. F60 presented higher SOD activity than the wt strain in planktonic and biofilm cultures, and iron deprivation increased K279a SOD activity. Under iron starvation, SDS-PAGE profile from K279a presented two iron-repressed proteins. Mass spectrometry analysis revealed homology with FepA and another putative TonB-dependent siderophore receptor of K279a. In silico analysis allowed the detection of potential Fur boxes in the respective coding genes. K279a encodes the QS diffusible signal factor (DSF). Under iron restriction K279a produced higher amounts of DSF than under iron rich condition. Finally...

‣ Xanthomonas campestris cell–cell signalling molecule DSF (diffusible signal factor) elicits innate immunity in plants and is suppressed by the exopolysaccharide xanthan

Kakkar, Akanksha; Nizampatnam, Narasimha Rao; Kondreddy, Anil; Pradhan, Binod Bihari; Chatterjee, Subhadeep
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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The Xanthomonas conserved cell–cell quorum-sensing molecule elicits innate immunity in plants. The defence response provoked by DSF is suppressed by the exopolysaccharide xanthan, a quorum-sensing-regulated virulence factor.

‣ Structural and Functional Characterization of Diffusible Signal Factor Family Quorum-Sensing Signals Produced by Members of the Burkholderia cepacia Complex▿

Deng, Yinyue; Wu, Ji'en; Eberl, Leo; Zhang, Lian-Hui
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Previous work has shown that Burkholderia cenocepacia produces the diffusible signal factor (DSF) family signal cis-2-dodecenoic acid (C12:Δ2, also known as BDSF), which is involved in the regulation of virulence. In this study, we determined whether C12:Δ2 production is conserved in other members of the Burkholderia cepacia complex (Bcc) by using a combination of high-performance liquid chromatography, mass spectrometry, and bioassays. Our results show that five Bcc species are capable of producing C12:Δ2 as a sole DSF family signal, while four species produce not only C12:Δ2 but also a new DSF family signal, which was identified as cis,cis-11-methyldodeca-2,5-dienoic acid (11-Me-C12:Δ2,5). In addition, we demonstrate that the quorum-sensing signal cis-11-methyl-2-dodecenoic acid (11-Me-C12:Δ2), which was originally identified in Xanthomonas campestris supernatants, is produced by Burkholderia multivorans. It is shown that, similar to 11-Me-C12:Δ2 and C12:Δ2, the newly identified molecule 11-Me-C12:Δ2,5 is a potent signal in the regulation of biofilm formation, the production of virulence factors, and the morphological transition of Candida albicans. These data provide evidence that DSF family molecules are highly conserved bacterial cell-cell communication signals that play key roles in the ecology of the organisms that produce them.

‣ Regulación de factores de virulencia y biofilm en Xanthomonas spp; Regulation of virulence factors and biofilm in Xanthomonas spp.

Torres, Pablo Sebastián
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2009 Português
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Xanthomonas campestris pv. campestris (Xcc) y Xanthomonas axonopodis pv. citri (Xac) son los agentes causales de la pudrición negra en crucíferas y de la cancrosis de los cítricos, respectivamente. En ambas bacterias la producción de diversos factores de virulencia está regulada por un grupo de genes denominados rpf (por regulation of pathogenicity factors) a través de la síntesis y percepción de moléculas difusibles que ellas mismas producen y que se denominan DSF (diffusible signal factor). RpfF y RpfB son responsables de la biosíntesis de DSF y RpfC y RpfG están involucrados en su detección y posterior transducción de la señal al interior de la bacteria. Mutaciones en los genes rpfF y rpfC producen una reducción en la producción de enzimas y polisacáridos extracelulares, formación de biofilm y patogenicidad cuando son comparadas con las respectivas cepas silvestres, lo que involucra a estos genes en la regulación de factores involucrados en todos éstos procesos. Entre éstos, hemos detectado un nuevo factor que es secretado por Xcc, que tiene la propiedad de revertir el cierre de estomas inducido por ácido Absísico (ABA), Lipopolisacárido (LPS) o bacterias. Las mutantes rprF y rpfC no pueden revertir el cierre de estomas...

‣ Caracterització del quorum sensing regulat per les N-acil-L-homoserina lactonas en Stenotrophomonas maltophilia

Martínez Alcalá, Paula
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion
Publicado em //2014 Português
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Els senyals de quorum sensing (QS) del tipus N-acil-L-homoserina lactonas (AHLs) són les molècules predominants detectades entre els proteobacteris. En el sistema de QS regulat per les AHLs intervenen dues proteïnes que pertanyen a la família del tipus LuxI i LuxR. Les proteïnes LuxI sintetitzen AHLs que interactuen amb un domini específic de les proteïnes LuxR. Aquest complex s'uneix a seqüències promotores específiques i permeten a la població bacteriana coordinar l'expressió gènica. En molts bacteris gram negatius, aquest sistema regula factors de virulència. L'objectiu principal d'aquest treball ha estat la identificació i caracterització de les molècules senyal del tipus AHLs i determinar diferents fenotips associats al QS mitjançant l'estudi del regulador del sistema (luxR) en Stenotrophomonas maltophilia, un patogen humà oportunista intrahospitalari emergent. Així, l'estudi s'ha centrat en primer terme en la detecció d'AHLs en diferents aïllats clínics d'aquest patogen, en concret de les soques E77, M30 i K279a. La detecció d'AHLs s'ha dut a terme emprant la soca biosensora d'Agrobacterium tumefaciens KYC55 i, posteriorment, les AHLs s'han caracteritzat per espectrometria de masses. S'ha fet també un estudi del promotor del gen luxR...