Articoli di riviste: "Vibrio. luxR"

1

Bazhenov, Sergey, Olga Melkina, Vadim Fomin, Ekaterina Scheglova, Pavel Krasnik, Svetlana Khrulnova, Gennadii Zavilgelsky e Ilya Manukhov. "LitR directly upregulates autoinducer synthesis and luminescence in Aliivibrio logei". PeerJ 9 (21 settembre 2021): e12030. http://dx.doi.org/10.7717/peerj.12030.

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LitR is a master-regulator of transcription in the ainS/R and luxS/PQ quorum sensing (QS) systems of bacteria from Vibrio and Aliivibrio genera. Here, we for the first time directly investigated the influence of LitR on gene expression in the luxI/R QS system of psychrophilic bacteria Aliivibrio logei. Investigated promoters were fused with Photorhabdus luminescens luxCDABE reporter genes cassette in a heterological system of Escherichia coli cells, litR A. logei was introduced into the cells under control of Plac promoter. LitR has been shown to upregulate genes of autoinducer synthase (luxI), luciferase and reductase (luxCDABE), and this effect doesn’t depend on presence of luxR gene. To a much lesser degree, LitR induces luxR1, but not the luxR2 — the main luxI/R regulator. Enhanced litR expression leads to an increase in a LuxI-autoinducer synthesis and a subsequent LuxR-mediated activation of the luxI/R QS system. Effect of LitR on luxI transcription depends on lux-box sequence in luxI promoter even in absence of luxR (lux-box is binding site of LuxR). The last finding indicates a direct interaction of LitR with the promoter in the lux-box region. Investigation of the effect of LitR A. logei on luxI/R QS systems of mesophilic Aliivibrio fischeri and psychrophilic Aliivibrio salmonicida showed direct luxR-independent upregulation of luxI and luxCDABE genes. To a lesser degree, it induces luxR A. fischeri and luxR1 A. salmonicida. Therefore, we assume that the main role of LitR in cross-interaction of these three QS systems is stimulating the expression of luxI.

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Antunes, Luis Caetano M., Rosana B. R. Ferreira, C. Phoebe Lostroh e E. Peter Greenberg. "A Mutational Analysis Defines Vibrio fischeri LuxR Binding Sites". Journal of Bacteriology 190, n. 13 (14 dicembre 2007): 4392–97. http://dx.doi.org/10.1128/jb.01443-07.

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ABSTRACT Vibrio fischeri quorum sensing involves the LuxI and LuxR proteins. The LuxI protein generates the quorum-sensing signal N-3-oxohexanoyl-l-homoserine lactone (3OC6-HSL), and LuxR is a signal-responsive transcriptional regulator which activates the luminescence (lux) genes and 17 other V. fischeri genes. For activation of the lux genes, LuxR binds to a 20-base-pair inverted repeat, the lux box, which is centered 42.5 base pairs upstream of the transcriptional start of the lux operon. Similar lux box-like elements have been identified in only a few of the LuxR-activated V. fischeri promoters. To better understand the DNA sequence elements required for LuxR binding and to identify binding sites in LuxR-regulated promoters other than the lux operon promoter, we have systematically mutagenized the lux box and evaluated the activity of many mutants. By doing so, we have identified nucleotides that are critical for promoter activity. Interestingly, certain lux box mutations allow a 3OC6-HSL-independent LuxR activation of the lux operon promoter. We have used the results of the mutational analysis to create a consensus lux box, and we have used this consensus sequence to identify LuxR binding sites in 3OC6-HSL-activated genes for which lux boxes could not be identified previously.

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Urbanowski, M. L., C. P. Lostroh e E. P. Greenberg. "Reversible Acyl-Homoserine Lactone Binding to Purified Vibrio fischeri LuxR Protein". Journal of Bacteriology 186, n. 3 (1 febbraio 2004): 631–37. http://dx.doi.org/10.1128/jb.186.3.631-637.2004.

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ABSTRACT The Vibrio fischeri LuxR protein is the founding member of a family of acyl-homoserine lactone-responsive quorum-sensing transcription factors. Previous genetic evidence indicates that in the presence of its quorum-sensing signal, N-(3-oxohexanoyl) homoserine lactone (3OC6-HSL), LuxR binds to lux box DNA within the promoter region of the luxI gene and activates transcription of the luxICDABEG luminescence operon. We have purified LuxR from recombinant Escherichia coli. Purified LuxR binds specifically and with high affinity to DNA containing a lux box. This binding requires addition of 3OC6-HSL to the assay reactions, presumably forming a LuxR-3OC6-HSL complex. When bound to the lux box at the luxI promoter in vitro, LuxR-3OC6-HSL enables E. coli RNA polymerase to initiate transcription from the luxI promoter. Unlike the well-characterized LuxR homolog TraR in complex with its signal (3-oxo-octanoyl-HSL), the LuxR-30C6-HSL complex can be reversibly inactivated by dilution, suggesting that 3OC6-HSL in the complex is not tightly bound and is in equilibrium with the bulk solvent. Thus, although LuxR and TraR both bind 3-oxoacyl-HSLs, the binding is qualitatively different. The differences have implications for the ways in which these proteins respond to decreases in signal concentrations or rapid drops in population density.

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4

Egland, Kristi A., e E. P. Greenberg. "Conversion of the Vibrio fischeriTranscriptional Activator, LuxR, to a Repressor". Journal of Bacteriology 182, n. 3 (1 febbraio 2000): 805–11. http://dx.doi.org/10.1128/jb.182.3.805-811.2000.

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ABSTRACT The Vibrio fischeri luminescence (lux) operon is regulated by a quorum-sensing system that involves the transcriptional activator (LuxR) and an acyl-homoserine lactone signal. Transcriptional activation requires the presence of a 20-base inverted repeat termed the lux box at a position centered 42.5 bases upstream of the transcriptional start of the lux operon. LuxR has proven difficult to study in vitro. A truncated form of LuxR has been purified, and together with ς70 RNA polymerase it can activate transcription of the lux operon. Both the truncated LuxR and RNA polymerase are required for binding tolux regulatory DNA in vitro. We have constructed an artificial lacZ promoter with the lux box positioned between and partially overlapping the consensus −35 and −10 hexamers of an RNA polymerase binding site. LuxR functioned as an acyl-homoserine lactone-dependent repressor at this promoter in recombinant Escherichia coli. Furthermore, multiplelux boxes on an independent replicon reduced the repressor activity of LuxR. Thus, it appears that LuxR can bind tolux boxes independently of RNA polymerase binding to the promoter region. A variety of LuxR mutant proteins were studied, and with one exception there was a correlation between function as a repressor of the artificial promoter and activation of a nativelux operon. The exception was the truncated protein that had been purified and studied in vitro. This protein functioned as an activator but not as a repressor in E. coli. The data indicate that the mutual dependence of purified, truncated LuxR and RNA polymerase on each other for binding to the lux promoter is a feature specific to the truncated LuxR and that full-length LuxR by itself can bind to lux box-containing DNA.

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5

Antunes, Luis Caetano M., Amy L. Schaefer, Rosana B. R. Ferreira, Nan Qin, Ann M. Stevens, Edward G. Ruby e E. Peter Greenberg. "Transcriptome Analysis of the Vibrio fischeri LuxR-LuxI Regulon". Journal of Bacteriology 189, n. 22 (7 settembre 2007): 8387–91. http://dx.doi.org/10.1128/jb.00736-07.

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ABSTRACT The Vibrio fischeri quorum-sensing signal N-3-oxohexanoyl-l-homoserine lactone (3OC6-HSL) activates expression of the seven-gene luminescence operon. We used microarrays to unveil 18 additional 3OC6-HSL-controlled genes, 3 of which had been identified by other means previously. We show most of these genes are regulated by the 3OC6-HSL-responsive transcriptional regulator LuxR directly. This demonstrates that V. fischeri quorum sensing regulates a substantial number of genes other than those involved in light production.

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6

Zhang, Jun, Bing Liu, Dan Gu, Yuan Hao, Mo Chen, Yue Ma, Xiaohui Zhou, David Reverter, Yuanxing Zhang e Qiyao Wang. "Binding site profiles and N-terminal minor groove interactions of the master quorum-sensing regulator LuxR enable flexible control of gene activation and repression". Nucleic Acids Research 49, n. 6 (8 marzo 2021): 3274–93. http://dx.doi.org/10.1093/nar/gkab150.

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Abstract LuxR is a TetR family master quorum sensing (QS) regulator activating or repressing expression of hundreds of genes that control collective behaviors in Vibrios with underlying mechanism unknown. To illuminate how this regulator controls expression of various target genes, we applied ChIP-seq and DNase I-seq technologies. Vibrio alginolyticus LuxR controls expression of ∼280 genes that contain either symmetric palindrome (repDNA) or asymmetric (actDNA) binding motifs with different binding profiles. The median number of LuxR binding sites for activated genes are nearly double for that of repressed genes. Crystal structures of LuxR in complex with the respective repDNA and actDNA motifs revealed a new mode of LuxR DNA binding that involves contacts of its N-terminal extension to the minor groove. The N-terminal contacts mediated by Arginine-9 and Arginine-11 differ when LuxR binds to repDNA vs actDNA, leading to higher binding affinity at repressed targets. Moreover, modification of LuxR binding sites, binding profiles, and N-terminal extension have important consequences on QS-regulated phenotypes. These results facilitate fundamental understanding of the high flexibility of mechanisms of LuxR control of gene activation and repression in Vibrio QS, which may facilitate to design QS inhibiting chemicals that interfere with LuxR regulation to effectively control pathogens.

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7

Callahan, Sean M., e Paul V. Dunlap. "LuxR- and Acyl-Homoserine-Lactone-Controlled Non-luxGenes Define a Quorum-Sensing Regulon in Vibrio fischeri". Journal of Bacteriology 182, n. 10 (15 maggio 2000): 2811–22. http://dx.doi.org/10.1128/jb.182.10.2811-2822.2000.

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ABSTRACT 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, andluxR 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, andribB 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 ribBpromoter regions each contained a sequence similar to thelux operon lux box, a 20-bp region of dyad symmetry necessary for LuxR/3-oxo-C6-HSL-dependent activation oflux operon transcription. V. fischeri qsrP andribB 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.

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Qin, Nan, Sean M. Callahan, Paul V. Dunlap e Ann M. Stevens. "Analysis of LuxR Regulon Gene Expression during Quorum Sensing in Vibrio fischeri". Journal of Bacteriology 189, n. 11 (30 marzo 2007): 4127–34. http://dx.doi.org/10.1128/jb.01779-06.

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ABSTRACT The regulation of the lux operon (luxICDABEG) of Vibrio fischeri has been intensively studied as a model for quorum sensing in proteobacteria. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis previously identified several non-Lux proteins in V. fischeri MJ-100 whose expression was dependent on LuxR and 3-oxo-hexanoyl-l-homoserine lactone (3-oxo-C6-HSL). To determine if the LuxR-dependent regulation of the genes encoding these proteins was due to direct transcriptional control by LuxR and 3-oxo-C6-HSL or instead was due to indirect control via an unidentified regulatory element, promoters of interest were cloned into a lacZ reporter and tested for their LuxR and 3-oxo-C6-HSL dependence in recombinant Escherichia coli. The promoters for qsrP, acfA, and ribB were found to be directly activated via LuxR-3-oxo-C6-HSL. The sites of transcription initiation were established via primer extension analysis. Based on this information and the position of the lux box-binding site near position −40, all three promoters appear to have a class II-type promoter structure. In order to more fully characterize the LuxR regulon in V. fischeri MJ-100, real-time reverse transcription-PCR was used to study the temporal expression of qsrP, acfA, and ribB during the exponential and stationary phases of growth, and electrophoretic mobility shift assays were used to compare the binding affinities of LuxR to the promoters under investigation. Taken together, the results demonstrate that regulation of the production of QsrP, RibB, and AcfA is controlled directly by LuxR at the level of transcription, thereby establishing that there is a LuxR regulon in V. fischeri MJ-100 whose genes are coordinately expressed during mid-exponential growth.

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McDougald, Diane, Scott A. Rice e Staffan Kjelleberg. "SmcR-Dependent Regulation of Adaptive Phenotypes inVibrio vulnificus". Journal of Bacteriology 183, n. 2 (15 gennaio 2001): 758–62. http://dx.doi.org/10.1128/jb.183.2.758-762.2001.

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ABSTRACT Vibrio vulnificus contains homologues of the V. harveyi luxR and luxS genes. A null mutation insmcR (luxR) resulted in a defect in starvation survival, inhibition of starvation-induced maintenance of culturability that occurs when V. vulnificusis starved prior to low-temperature incubation, and increased expression of stationary-phase phenotypes.

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10

Miyamoto, Carol M., Paul V. Dunlap, Edward G. Ruby e Edward A. Meighen. "LuxO controls luxR expression in Vibrio harveyi: evidence for a common regulatory mechanism in Vibrio". Molecular Microbiology 48, n. 2 (4 aprile 2003): 537–48. http://dx.doi.org/10.1046/j.1365-2958.2003.03453.x.

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11

McCarter, Linda L. "OpaR, a Homolog of Vibrio harveyi LuxR, Controls Opacity of Vibrio parahaemolyticus". Journal of Bacteriology 180, n. 12 (15 giugno 1998): 3166–73. http://dx.doi.org/10.1128/jb.180.12.3166-3173.1998.

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ABSTRACT Vibrio parahaemolyticus is an organism well adapted to communal life on surfaces. When grown on a surface or in a viscous layer, the bacterium induces a large gene system and differentiates to swarmer cells capable of movement over and colonization of surfaces.V. parahaemolyticus displays additional phenotypic versatility manifested as variable colony morphology, switching between translucent and opaque colony types. Although not itself luminescent,V. parahaemolyticus produces autoinducer molecules capable of inducing luminescence in Vibrio harveyi. To examine the role of quorum signaling in the lifestyles of V. parahaemolyticus, the functional homolog of the gene encoding theV. harveyi autoinducer-controlled transcriptional regulatory protein LuxR was cloned. Sequence analysis of the clone predicted an open reading frame with a deduced product 96% identical to LuxR. Introduction of the clone carrying the luxR-like locus into V. parahaemolyticus dramatically affected colony morphology, converting a translucent strain to an opaque one. When the coding sequence for the luxR homolog was placed under the control of the Ptac promoter, conversion to the opaque phenotype became inducible by isopropyl-β-d-thiogalactopyranoside. Allelic disruption of the luxR-like gene on the chromosome of an opaque strain produced a translucent strain proficient in swarming ability. Primer extension mapping demonstrated opaRtranscription in opaque but not translucent cell types. It is postulated that this gene, which has been named opaR, encodes a transcription factor controlling cell type. The underlying genetic basis for opaque-translucent variation may be the consequence of a genomic alteration detected in the opaR locus of opaque and translucent strains.

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Trott, Amy E., e Ann M. Stevens. "Amino Acid Residues in LuxR Critical for Its Mechanism of Transcriptional Activation during Quorum Sensing inVibrio fischeri". Journal of Bacteriology 183, n. 1 (1 gennaio 2001): 387–92. http://dx.doi.org/10.1128/jb.183.1.387-392.2001.

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ABSTRACT PCR-based site-directed mutagenesis has been used to generate 38 alanine-substitution mutations in the C-terminal 41 amino acid residues of LuxR. This region plays a critical role in the mechanism of LuxR-dependent transcriptional activation of the Vibrio fischeri lux operon during quorum sensing. The ability of the variant forms of LuxR to activate transcription of the lux operon was examined by using in vivo assays in recombinant Escherichia coli. Eight recombinant strains produced luciferase at levels less than 50% of that of a strain expressing wild-type LuxR. Western immunoblotting analysis verified that the altered forms of LuxR were expressed at levels equivalent to those of the wild type. An in vivo DNA binding-repression assay in recombinant E. coli was subsequently used to measure the ability of the variant forms of LuxR to bind to the lux box, the binding site of LuxR at thelux operon promoter. All eight LuxR variants found to affect cellular luciferase levels were unable to bind to thelux box. An additional 11 constructs that had no effect on cellular luciferase levels were also found to exhibit a defect in DNA binding. None of the alanine substitutions in LuxR affected activation of transcription of the lux operon without also affecting DNA binding. These results support the conclusion that the C-terminal 41 amino acids of LuxR are important for DNA recognition and binding of the lux box rather than positive control of the process of transcription initiation.

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Stevens, Ann M., Nobuyuki Fujita, Akira Ishihama e E. P. Greenberg. "Involvement of the RNA Polymerase α-Subunit C-Terminal Domain in LuxR-Dependent Activation of the Vibrio fischeri Luminescence Genes". Journal of Bacteriology 181, n. 15 (1 agosto 1999): 4704–7. http://dx.doi.org/10.1128/jb.181.15.4704-4707.1999.

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ABSTRACT LuxR is a ς70 RNA polymerase (RNAP)-dependent transcriptional activator that controls expression of the Vibrio fischeri lux operon in response to an acylhomoserine lactone-cell density signal. We have investigated whether the α-subunit C-terminal domain (αCTD) of RNAP is required for LuxR activity. A purified signal-independent, LuxR C-terminal domain-containing polypeptide (LuxRΔN) was used to study the activation of transcription from theluxI promoter in vitro. Initiation of luxoperon transcription was observed in the presence of LuxRΔN and wild-type RNAP but not in the presence of LuxRΔN and RNAPs with truncated αCTDs. We also studied the in vivo role of the RNAP αCTD in activation of lux transcription in Escherichia coli. This enabled a comparison of results obtained with full-length LuxR to those obtained with LuxRΔN. These in vivo studies indicated that both LuxR and LuxRΔN require the RNAP αCTD for activity. The results of DNase I protection studies showed that LuxRΔN-RNAP complexes can bind and protect the luxIpromoter, but with less efficacy when the αCTD is truncated in comparison to the wild type. Thus, both in vitro and in vivo experiments demonstrated that LuxR-dependent transcriptional activation of the lux operon involves the RNAP αCTD and suggest that αCTD-LuxR interactions may play a role in recruitment of RNAP to theluxI promoter.

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Shao, Chung-Ping, e Lien-I. Hor. "Regulation of Metalloprotease Gene Expression in Vibrio vulnificus by a Vibrio harveyi LuxR Homologue". Journal of Bacteriology 183, n. 4 (15 febbraio 2001): 1369–75. http://dx.doi.org/10.1128/jb.183.4.1369-1375.2001.

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ABSTRACT Expression of the Vibrio vulnificus metalloprotease gene, vvp, was turned up rapidly when bacterial growth reached the late log phase. A similar pattern of expression has been found in the metalloprotease gene of Vibrio cholerae, and this has been shown to be regulated by a Vibrio harveyiLuxR-like transcriptional activator. To find out whether a LuxR homologue exists in V. vulnificus, a gene library of this organism was screened by colony hybridization using a probe derived from a sequence that is conserved in various luxR-like genes of vibrios. A gene containing a 618-bp open reading frame was identified and found to be identical to the smcR gene ofV. vulnificus reported previously. An isogenic SmcR-deficient (RD) mutant was further constructed by an in vivo allelic exchange technique. This mutant exhibited an extremely low level of vvp transcription compared with that of the parent strain. On the other hand, the cytolysin gene, vvhA, was expressed at a higher level in the RD mutant than in the parent strain during the log phase of growth. These data suggested that SmcR might not only be a positive regulator of the protease gene but might also be involved in negative regulation of the cytolysin gene. Virulence of the RD mutant in either normal or iron-overloaded mice challenged by intraperitoneal injection was comparable to that of the parent strain, indicating that SmcR is not required for V. vulnificusvirulence in mice.

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Hawkins, Andrew C., Frances H. Arnold, Rainer Stuermer, Bernhard Hauer e Jared R. Leadbetter. "Directed Evolution of Vibrio fischeri LuxR for Improved Response to Butanoyl-Homoserine Lactone". Applied and Environmental Microbiology 73, n. 18 (3 agosto 2007): 5775–81. http://dx.doi.org/10.1128/aem.00060-07.

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ABSTRACT LuxR is the 3-oxohexanoyl-homoserine lactone (3OC6HSL)-dependent transcriptional activator of the prototypical acyl-homoserine lactone (AHL) quorum-sensing system of Vibrio fischeri. Wild-type LuxR exhibits no response to butanoyl-HSL (C4HSL) in quantitative bioassays at concentrations of up to 1 μM; a previously described LuxR variant (LuxR-G2E) exhibits a broadened response to diverse AHLs, including pentanoyl-HSL (C5HSL), but not to C4HSL. Here, two rounds of directed evolution of LuxR-G2E generated variants of LuxR that responded to C4HSL at concentrations as low as 10 nM. One variant, LuxR-G4E, had only one change, I45F, relative to the parent LuxR-G2E, which itself differs from the wild type at three residues. Dissection of the four mutations within LuxR-G4E demonstrated that at least three of these changes were simultaneously required to achieve any measurable C4HSL response. The four changes improved both sensitivity and specificity towards C4HSL relative to any of the other 14 possible combinations of those residues. These data confirm that LuxR is evolutionarily pliable and suggest that LuxR is not intrinsically asymmetric in its response to quorum-sensing signals with different acyl-side-chain lengths.

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O'Grady, Elizabeth A., e Charles F. Wimpee. "Mutations in the lux Operon of Natural Dark Mutants in the Genus Vibrio". Applied and Environmental Microbiology 74, n. 1 (2 novembre 2007): 61–66. http://dx.doi.org/10.1128/aem.01199-07.

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ABSTRACT Bacterial bioluminescence can display a wide range of intensities among strains, from very bright to undetectable, and it has been shown previously that there are nonluminous vibrios that possess lux genes. In this paper, we report the isolation and characterization of completely dark natural mutants in the genus Vibrio. Screening of over 600 Vibrio isolates with a luxA gene probe revealed that approximately 5% carried the luxA gene. Bioluminescence assays of the luxA-positive isolates, followed by repetitive extragenic palindromic-PCR fingerprinting, showed three unique genotypes that are completely dark. The dark mutants show a variety of lesions, including an insertion sequence, point mutations, and deletions. Strain BCB451 has an IS10 insertion sequence in luxA, a mutated luxE stop codon, and a truncated luxH. Strain BCB494 has a 396-bp deletion in luxC, and strain BCB440 has a frameshift in luxC. This paper represents the first molecular characterization of natural dark mutants and the first demonstration of incomplete lux operons in natural isolates.

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Perry, Lynda L., Nathan G. Bright, Richard J. Carroll, Jr., M. Cathy Scott, Michael S. Allen e Bruce M. Applegate. "Molecular characterization of autoinduction of bioluminescence in the Microtox® indicator strain Vibrio fischeri ATCC 49387". Canadian Journal of Microbiology 51, n. 7 (1 luglio 2005): 549–57. http://dx.doi.org/10.1139/w05-019.

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Repeated attempts to clone the luxI from Vibrio fischeri ATCC 49387 failed to produce a clone carrying a functional LuxI. Sequence data from the clones revealed the presence of a polymorphism when compared with previously published luxI sequences, prompting further characterization of bioluminescence regulation in V. fischeri ATCC 49387. Further investigation of V. fischeri ATCC 49387 revealed that its LuxI protein lacks detectable LuxI activity due to the presence of a glutamine residue at position 125 in the deduced amino acid sequence. Specific bioluminescence in V. fischeri ATCC 49387 increases with increasing cell density, indicative of a typical autoinduction response. However, conditioned medium from this strain does not induce bioluminescence in an ATCC 49387 luxR-plux-based acyl homoserine lactone reporter strain, but does induce bioluminescence in ATCC 49387. It has been previously shown that a V. fischeri MJ-1 luxI mutant exhibits autoinduction of bioluminescence through N-octanoyl-L-homoserine lactone, the product of the AinS autoinducer synthase. However, a bioreporter based on luxR-plux from V. fischeri ATCC 49387 responded poorly to conditioned medium from V. fischeri ATCC 49387 and also responded poorly to authentic N-octanoyl-DL-homoserine lactone. A similar MJ-1-based bioreporter showed significant induction under the same conditions. A putative ainS gene cloned from ATCC 49387, unlike luxI from ATCC 49387, expresses V. fischeri autoinducer synthase activity in Escherichia coli. This study suggests that a regulatory mechanism independent of LuxR and LuxI but possibly involving AinS is responsible for the control of autoinduction of bioluminescence in V. fischeri ATCC 49387.Key words: quorum sensing, bioluminescence, Vibrio fischeri.

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Williams, Joshua W., A. L. Ritter e Ann M. Stevens. "CsrA modulates luxR transcript levels in Vibrio fischeri". FEMS Microbiology Letters 329, n. 1 (8 febbraio 2012): 28–35. http://dx.doi.org/10.1111/j.1574-6968.2012.02499.x.

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Kimura, Yuki, Yohei Tashiro, Kyoichi Saito, Shigeko Kawai-Noma e Daisuke Umeno. "Directed evolution of Vibrio fischeri LuxR signal sensitivity". Journal of Bioscience and Bioengineering 122, n. 5 (novembre 2016): 533–38. http://dx.doi.org/10.1016/j.jbiosc.2016.04.010.

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Plener, Laure, Nicola Lorenz, Matthias Reiger, Tiago Ramalho, Ulrich Gerland e Kirsten Jung. "The Phosphorylation Flow of the Vibrio harveyi Quorum-Sensing Cascade Determines Levels of Phenotypic Heterogeneity in the Population". Journal of Bacteriology 197, n. 10 (9 marzo 2015): 1747–56. http://dx.doi.org/10.1128/jb.02544-14.

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ABSTRACTQuorum sensing (QS) is a communication process that enables a bacterial population to coordinate and synchronize specific behaviors. The bioluminescent marine bacteriumVibrio harveyiintegrates three autoinducer (AI) signals into one quorum-sensing cascade comprising a phosphorelay involving three hybrid sensor kinases: LuxU; LuxO, an Hfq/small RNA (sRNA) switch; and the transcriptional regulator LuxR. Using a new set ofV. harveyimutants lacking genes for the AI synthases and/or sensors, we assayed the activity of the quorum-sensing cascade at the population and single-cell levels, with a specific focus on signal integration and noise levels. We found that the ratios of kinase activities to phosphatase activities of the three sensors and, hence, the extent of phosphorylation of LuxU/LuxO are important not only for the signaling output but also for the degree of noise in the system. The pools of phosphorylated LuxU/LuxO per cell directly determine the amounts of sRNAs produced and, consequently, the copy number of LuxR, generating heterogeneous quorum-sensing activation at the single-cell level. We conclude that the ability to drive the heterogeneous expression of QS-regulated genes inV. harveyiis an inherent feature of the architecture of the QS cascade.IMPORTANCEV. harveyipossesses one of the most complex quorum-sensing (QS) cascades known, using three different autoinducers (AIs) to control the induction of, e.g., bioluminescence, virulence factors, and biofilm and exoprotease production. We constructed variousV. harveyimutants to study the impact of each component and subsystem of the QS signaling cascade on QS activation at the population and single-cell levels. We found that the output was homogeneous only in the presence of all AIs. In the absence of any one AI, QS activation varied from cell to cell, resulting in phenotypic heterogeneity. This study elucidates a molecular design principle which enables a tightly integrated signaling cascade to control the expression of diverse phenotypes within a genetically homogeneous population.

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21

Nelson, Eric J., Hege S. Tunsjø, Pat M. Fidopiastis, Henning Sørum e Edward G. Ruby. "A Novel lux Operon in the Cryptically Bioluminescent Fish Pathogen Vibrio salmonicida Is Associated with Virulence". Applied and Environmental Microbiology 73, n. 6 (2 febbraio 2007): 1825–33. http://dx.doi.org/10.1128/aem.02255-06.

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ABSTRACT The cold-water-fish pathogen Vibrio salmonicida expresses a functional bacterial luciferase but produces insufficient levels of its aliphatic-aldehyde substrate to be detectably luminous in culture. Our goals were to (i) better explain this cryptic bioluminescence phenotype through molecular characterization of the lux operon and (ii) test whether the bioluminescence gene cluster is associated with virulence. Cloning and sequencing of the V. salmonicida lux operon revealed that homologs of all of the genes required for luminescence are present: luxAB (luciferase) and luxCDE (aliphatic-aldehyde synthesis). The arrangement and sequence of these structural lux genes are conserved compared to those in related species of luminous bacteria. However, V. salmonicida strains have a novel arrangement and number of homologs of the luxR and luxI quorum-sensing regulatory genes. Reverse transcriptase PCR analysis suggests that this novel arrangement of quorum-sensing genes generates antisense transcripts that may be responsible for the reduced production of bioluminescence. In addition, infection with a strain in which the luxA gene was mutated resulted in a marked delay in mortality among Atlantic salmon relative to infection with the wild-type parent in single-strain challenge experiments. In mixed-strain competition between the luxA mutant and the wild type, the mutant was attenuated up to 50-fold. It remains unclear whether the attenuation results from a direct loss of luciferase or a polar disturbance elsewhere in the lux operon. Nevertheless, these findings document for the first time an association between a mutation in a structural lux gene and virulence, as well as provide a new molecular system to study Vibrio pathogenesis in a natural host.

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22

Chatterjee, Jaidip, Carol M. Miyamoto e Edward A. Meighen. "Autoregulation of luxR: the Vibrio harveyi lux-operon activator functions as a repressor". Molecular Microbiology 20, n. 2 (aprile 1996): 415–25. http://dx.doi.org/10.1111/j.1365-2958.1996.tb02628.x.

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23

Finney, Angela H., Robert J. Blick, Katsuhiko Murakami, Akira Ishihama e Ann M. Stevens. "Role of the C-Terminal Domain of the Alpha Subunit of RNA Polymerase in LuxR-Dependent Transcriptional Activation of the lux Operon during Quorum Sensing". Journal of Bacteriology 184, n. 16 (15 agosto 2002): 4520–28. http://dx.doi.org/10.1128/jb.184.16.4520-4528.2002.

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ABSTRACT During quorum sensing in Vibrio fischeri, the luminescence, or lux, operon is regulated in a cell density-dependent manner by the activator LuxR in the presence of an acylated homoserine lactone autoinducer molecule [N-(3-oxohexanoyl) homoserine lactone]. LuxR, which binds to the lux operon promoter at a position centered at −42.5 relative to the transcription initiation site, is thought to function as an ambidextrous activator making multiple contacts with RNA polymerase (RNAP). The specific role of the α-subunit C-terminal domain (αCTD) of RNAP in LuxR-dependent transcriptional activation of the lux operon promoter has been investigated. The effects of 70 alanine substitution variants of the α subunit were determined in vivo by measuring the rate of transcription of the lux operon via luciferase assays in recombinant Escherichia coli. The mutant RNAPs from strains exhibiting at least twofold-increased or -decreased activity in comparison to the wild type were further examined by in vitro assays. Since full-length LuxR has not been purified, an autoinducer-independent N-terminally truncated form of LuxR, LuxRΔN, was used for in vitro studies. Single-round transcription assays were performed using reconstituted mutant RNAPs in the presence of LuxRΔN, and 14 alanine substitutions in the αCTD were identified as having negative effects on the rate of transcription from the lux operon promoter. Five of these 14 α variants were also involved in the mechanisms of both LuxR- and LuxRΔN-dependent activation in vivo. The positions of these residues lie roughly within the 265 and 287 determinants in α that have been identified through studies of the cyclic AMP receptor protein and its interactions with RNAP. This suggests a model where residues 262, 265, and 296 in α play roles in DNA recognition and residues 290 and 314 play roles in α-LuxR interactions at the lux operon promoter during quorum sensing.

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24

Egland, Kristi A., e E. P. Greenberg. "Quorum Sensing in Vibrio fischeri: Analysis of the LuxR DNA Binding Region by Alanine-Scanning Mutagenesis". Journal of Bacteriology 183, n. 1 (1 gennaio 2001): 382–86. http://dx.doi.org/10.1128/jb.183.1.382-386.2001.

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ABSTRACT LuxR is the transcriptional activator for quorum-sensing control of luminescence in Vibrio fischeri. A series of alanine-scanning mutants spanning a predicted helix-turn-helix region in the DNA binding domain of LuxR was constructed, and the activity of each of the LuxR mutant proteins in recombinant Escherichia coli was investigated. The region covered by the mutagenesis spanned residues 190 to 224. About half of the alanine-scanning mutants showed activities similar to that of the wild-type LuxR: at least two were positive-control mutants, four appeared to be defective in DNA binding, and several others were characterized as DNA binding affinity mutants. This analysis, taken together with information about other bacterial transcription factors, provides insights into amino acid residues in LuxR that are involved in DNA binding and transcriptional activation.

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25

Rutherford, Steven T., Julie S. Valastyan, Thibaud Taillefumier, Ned S. Wingreen e Bonnie L. Bassler. "Comprehensive analysis reveals how single nucleotides contribute to noncoding RNA function in bacterial quorum sensing". Proceedings of the National Academy of Sciences 112, n. 44 (19 ottobre 2015): E6038—E6047. http://dx.doi.org/10.1073/pnas.1518958112.

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Five homologous noncoding small RNAs (sRNAs), called the Qrr1-5 sRNAs, function in the Vibrio harveyi quorum-sensing cascade to drive its operation. Qrr1-5 use four different regulatory mechanisms to control the expression of ∼20 mRNA targets. Little is known about the roles individual nucleotides play in mRNA target selection, in determining regulatory mechanism, or in defining Qrr potency and dynamics of target regulation. To identify the nucleotides vital for Qrr function, we developed a method we call RSort-Seq that combines saturating mutagenesis, fluorescence-activated cell sorting, high-throughput sequencing, and mutual information theory to explore the role that every nucleotide in Qrr4 plays in regulation of two mRNA targets, luxR and luxO. Companion biochemical assays allowed us to assign specific regulatory functions/underlying molecular mechanisms to each important base. This strategy yielded a regional map of nucleotides in Qrr4 vital for stability, Hfq interaction, stem-loop formation, and base pairing to both luxR and luxO, to luxR only, and to luxO only. In terms of nucleotides critical for sRNA function, the RSort-Seq analysis provided strikingly different results from those predicted by commonly used regulatory RNA-folding algorithms. This approach is applicable to any RNA–RNA interaction, including sRNAs in other bacteria and regulatory RNAs in higher organisms.

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26

White, Catharine E., e Stephen C. Winans. "Cell–cell communication in the plant pathogen Agrobacterium tumefaciens". Philosophical Transactions of the Royal Society B: Biological Sciences 362, n. 1483 (13 marzo 2007): 1135–48. http://dx.doi.org/10.1098/rstb.2007.2040.

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The plant pathogen Agrobacterium tumefaciens induces the formation of crown gall tumours at wound sites on host plants by directly transforming plant cells. This disease strategy benefits the bacteria as the infected plant tissue produces novel nutrients, called opines, that the colonizing bacteria can use as nutrients. Almost all of the genes that are required for virulence, and all of the opine uptake and utilization genes, are carried on large tumour-inducing (Ti) plasmids. The observation more than 25 years ago that specific opines are required for Ti plasmid conjugal transfer led to the discovery of a cell–cell signalling system on these plasmids that is similar to the LuxR–LuxI system first described in Vibrio fischeri . All Ti plasmids that have been described to date carry a functional LuxI-type N -acylhomoserine lactone synthase (TraI), and a LuxR-type signal receptor and transcriptional regulator called TraR. The traR genes are expressed only in the presence of specific opines called conjugal opines. The TraR–TraI system provides an important model for LuxR–LuxI-type systems, especially those found in the agriculturally important Rhizobiaceae family. In this review, we discuss current advances in the biochemistry and structural biology of the TraR–TraI system.

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27

Newman, Jane D., Meghan M. Russell, Lixin Fan, Yun-Xing Wang, Giovanni Gonzalez-Gutierrez e Julia C. van Kessel. "The DNA binding domain of the Vibrio vulnificus SmcR transcription factor is flexible and binds diverse DNA sequences". Nucleic Acids Research 49, n. 10 (22 maggio 2021): 5967–84. http://dx.doi.org/10.1093/nar/gkab387.

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Abstract Quorum sensing gene expression in vibrios is regulated by the LuxR/HapR family of transcriptional factors, which includes Vibrio vulnificus SmcR. The consensus binding site of Vibrio LuxR/HapR/SmcR proteins is palindromic but highly degenerate with sequence variations at each promoter. To examine the mechanism by which SmcR recognizes diverse DNA sites, we generated SmcR separation-of-function mutants that either repress or activate transcription but not both. SmcR N55I is restricted in recognition of single base-pair variations in DNA binding site sequences and thus is defective at transcription activation but retains interaction with RNA polymerase (RNAP) alpha. SmcR S76A, L139R and N142D substitutions disrupt the interaction with RNAP alpha but retain functional DNA binding activity. X-ray crystallography and small angle X-ray scattering data show that the SmcR DNA binding domain exists in two conformations (wide and narrow), and the protein complex forms a mixture of dimers and tetramers in solution. The three RNAP interaction-deficient variants also have two DNA binding domain conformations, whereas SmcR N55I exhibits only the wide conformation. These data support a model in which two mechanisms drive SmcR transcriptional activation: interaction with RNAP and a multi-conformational DNA binding domain that permits recognition of variable DNA sites.

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28

Lu, Yang. "Engineering Vibrio fischeri transcriptional activator LuxR for diverse transcriptional activities". Biotechnology Letters 38, n. 9 (3 giugno 2016): 1459–63. http://dx.doi.org/10.1007/s10529-016-2134-z.

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29

Swartzman, E., M. Silverman e E. A. Meighen. "The luxR gene product of Vibrio harveyi is a transcriptional activator of the lux promoter." Journal of Bacteriology 174, n. 22 (1992): 7490–93. http://dx.doi.org/10.1128/jb.174.22.7490-7493.1992.

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30

Shadel, G. S., e T. O. Baldwin. "Positive autoregulation of the Vibrio fischeri luxR gene. LuxR and autoinducer activate cAMP-catabolite gene activator protein complex-independent and -dependent luxR transcription." Journal of Biological Chemistry 267, n. 11 (aprile 1992): 7696–702. http://dx.doi.org/10.1016/s0021-9258(18)42571-9.

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31

Croxatto, Antony, Victoria J. Chalker, Johan Lauritz, Jana Jass, Andrea Hardman, Paul Williams, Miguel Cámara e Debra L. Milton. "VanT, a Homologue of Vibrio harveyi LuxR, Regulates Serine, Metalloprotease, Pigment, and Biofilm Production in Vibrio anguillarum". Journal of Bacteriology 184, n. 6 (15 marzo 2002): 1617–29. http://dx.doi.org/10.1128/jb.184.6.1617-1629.2002.

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ABSTRACT Vibrio anguillarum possesses at least two N-acylhomoserine lactone (AHL) quorum-sensing circuits, one of which is related to the luxMN system of Vibrio harveyi. In this study, we have cloned an additional gene of this circuit, vanT, encoding a V. harveyi LuxR-like transcriptional regulator. A V. anguillarum ΔvanT null mutation resulted in a significant decrease in total protease activity due to loss of expression of the metalloprotease EmpA, but no changes in either AHL production or virulence. Additional genes positively regulated by VanT were identified from a plasmid-based gene library fused to a promoterless lacZ. Three lacZ fusions (serA::lacZ, hpdA-hgdA::lacZ, and sat-vps73::lacZ) were identified which exhibited decreased expression in the ΔvanT strain. SerA is similar to 3-phosphoglycerate dehydrogenases and catalyzes the first step in the serine-glycine biosynthesis pathway. HgdA has identity with homogentisate dioxygenases, and HpdA is homologous to 4-hydroxyphenylpyruvate dioxygenases (HPPDs) involved in pigment production. V. anguillarum strains require an active VanT to produce high levels of an l-tyrosine-induced brown color via HPPD, suggesting that VanT controls pigment production. Vps73 and Sat are related to Vibrio cholerae proteins encoded within a DNA locus required for biofilm formation. A V. anguillarum ΔvanT mutant and a mutant carrying a polar mutation in the sat-vps73 DNA locus were shown to produce defective biofilms. Hence, a new member of the V. harveyi LuxR transcriptional activator family has been characterized in V. anguillarum that positively regulates serine, metalloprotease, pigment, and biofilm production.

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32

van Kessel, Julia C., Steven T. Rutherford, Jian-Ping Cong, Sofia Quinodoz, James Healy e Bonnie L. Bassler. "Quorum Sensing Regulates the Osmotic Stress Response in Vibrio harveyi". Journal of Bacteriology 197, n. 1 (13 ottobre 2014): 73–80. http://dx.doi.org/10.1128/jb.02246-14.

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Bacteria use a chemical communication process called quorum sensing to monitor cell density and to alter behavior in response to fluctuations in population numbers. Previous studies withVibrio harveyihave shown that LuxR, the master quorum-sensing regulator, activates and represses >600 genes. These include six genes that encode homologs of theEscherichia coliBet and ProU systems for synthesis and transport, respectively, of glycine betaine, an osmoprotectant used during osmotic stress. Here we show that LuxR activates expression of the glycine betaine operonbetIBA-proXWV, which enhances growth recovery under osmotic stress conditions. BetI, an autorepressor of theV. harveyibetIBA-proXWVoperon, activates the expression of genes encoding regulatory small RNAs that control quorum-sensing transitions. Connecting quorum-sensing and glycine betaine pathways presumably enablesV. harveyito tune its execution of collective behaviors to its tolerance to stress.

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33

Miyamoto, Carol M., Weiqun Sun e Edward A. Meighen. "The LuxR regulator protein controls synthesis of polyhydroxybutyrate in Vibrio harveyi". Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology 1384, n. 2 (maggio 1998): 356–64. http://dx.doi.org/10.1016/s0167-4838(98)00028-4.

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34

Miyamoto, Carol M., Eric E. Smith, Eiana Swartzman, Jie‐Gang Cao, Angus F. Graham e Edward A. Meighen. "Proximal and distal sites bind LuxR independently and activate expression of the Vibrio harveyi lux operon". Molecular Microbiology 14, n. 2 (ottobre 1994): 255–62. http://dx.doi.org/10.1111/j.1365-2958.1994.tb01286.x.

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35

Miyamoto, Carol M., Jaidip Chatterjee, Elana Swartzman, Rose Szittner e Edward A. Meighen. "The role of the lux autoinducer in regulating luminescence in Vibrio harveyi; control of luxR expression". Molecular Microbiology 19, n. 4 (febbraio 1996): 767–75. http://dx.doi.org/10.1046/j.1365-2958.1996.417948.x.

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36

Freeman, Jeremy A., e Bonnie L. Bassler. "Sequence and Function of LuxU: a Two-Component Phosphorelay Protein That Regulates Quorum Sensing inVibrio harveyi". Journal of Bacteriology 181, n. 3 (1 febbraio 1999): 899–906. http://dx.doi.org/10.1128/jb.181.3.899-906.1999.

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ABSTRACT Vibrio harveyi regulates the expression of bioluminescence (lux) in response to cell density, a phenomenon known as quorum sensing. In V. harveyi, two independent quorum-sensing systems exist, and each produces, detects, and responds to a specific cell density-dependent autoinducer signal. The autoinducers are recognized by two-component hybrid sensor kinases called LuxN and LuxQ, and sensory information from both systems is transduced by a phosphorelay mechanism to the response regulator protein LuxO. Genetic evidence suggests that LuxO-phosphate negatively regulates the expression of luminescence at low cell density in the absence of autoinducers. At high cell density, interaction of the sensors with their cognate autoinducers results in dephosphorylation and inactivation of the LuxO repressor. In the present report, we show that LuxN and LuxQ channel sensory information to LuxO via a newly identified phosphorelay protein that we have named LuxU. LuxU shows sequence similarity to other described phosphorelay proteins, including BvgS, ArcB, and Ypd1. A critical His residue (His 58) of LuxU is required for phosphorelay function.

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37

Dunlap, P. V., e E. P. Greenberg. "Control of Vibrio fischeri lux gene transcription by a cyclic AMP receptor protein-luxR protein regulatory circuit." Journal of Bacteriology 170, n. 9 (1988): 4040–46. http://dx.doi.org/10.1128/jb.170.9.4040-4046.1988.

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38

Waters, Christopher M., Julie T. Wu, Meghan E. Ramsey, Rebecca C. Harris e Bonnie L. Bassler. "Control of the Type 3 Secretion System in Vibrio harveyi by Quorum Sensing through Repression of ExsA". Applied and Environmental Microbiology 76, n. 15 (11 giugno 2010): 4996–5004. http://dx.doi.org/10.1128/aem.00886-10.

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ABSTRACT The type 3 secretion system (T3SS) genes of Vibrio harveyi are activated at low cell density and repressed at high cell density by quorum sensing (QS). Repression requires LuxR, the master transcriptional regulator of QS-controlled genes. Here, we determine the mechanism underlying the LuxR repression of the T3SS system. Using a fluorescence-based cell sorting approach, we isolated V. harveyi mutants that are unable to express T3SS genes at low cell density and identified two mutations in the V. harveyi exsBA operon. While LuxR directly represses the expression of exsBA, complementation and epistasis analyses reveal that it is the repression of exsA expression, but not exsB expression, that is responsible for the QS-mediated repression of T3SS genes at high cell density. The present work further defines the genes in the V. harveyi QS regulon and elucidates a mechanism demonstrating how multiple regulators can be linked in series to direct the expression of QS target genes specifically at low or high cell density.

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39

Schaefer, A. L., B. L. Hanzelka, A. Eberhard e E. P. Greenberg. "Quorum sensing in Vibrio fischeri: probing autoinducer-LuxR interactions with autoinducer analogs." Journal of bacteriology 178, n. 10 (1996): 2897–901. http://dx.doi.org/10.1128/jb.178.10.2897-2901.1996.

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40

Colton, Deanna M., Eric V. Stabb e Stephen J. Hagen. "Modeling Analysis of Signal Sensitivity and Specificity by Vibrio fischeri LuxR Variants". PLOS ONE 10, n. 5 (11 maggio 2015): e0126474. http://dx.doi.org/10.1371/journal.pone.0126474.

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41

Kolibachuk, D., e E. P. Greenberg. "The Vibrio fischeri luminescence gene activator LuxR is a membrane-associated protein." Journal of Bacteriology 175, n. 22 (1993): 7307–12. http://dx.doi.org/10.1128/jb.175.22.7307-7312.1993.

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42

Slock, J., D. VanRiet, D. Kolibachuk e E. P. Greenberg. "Critical regions of the Vibrio fischeri luxR protein defined by mutational analysis." Journal of Bacteriology 172, n. 7 (1990): 3974–79. http://dx.doi.org/10.1128/jb.172.7.3974-3979.1990.

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43

Tashiro, Yohei, Yuki Kimura, Maiko Furubayashi, Akira Tanaka, Kei Terakubo, Kyoichi Saito, Shigeko Kawai-Noma e Daisuke Umeno. "Directed evolution of the autoinducer selectivity of Vibrio fischeri LuxR". Journal of General and Applied Microbiology 62, n. 5 (2016): 240–47. http://dx.doi.org/10.2323/jgam.2016.04.005.

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44

Choi, S. H., e E. P. Greenberg. "The C-terminal region of the Vibrio fischeri LuxR protein contains an inducer-independent lux gene activating domain." Proceedings of the National Academy of Sciences 88, n. 24 (15 dicembre 1991): 11115–19. http://dx.doi.org/10.1073/pnas.88.24.11115.

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45

Stevens, A. M., K. M. Dolan e E. P. Greenberg. "Synergistic binding of the Vibrio fischeri LuxR transcriptional activator domain and RNA polymerase to the lux promoter region." Proceedings of the National Academy of Sciences 91, n. 26 (20 dicembre 1994): 12619–23. http://dx.doi.org/10.1073/pnas.91.26.12619.

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46

Devine, Jerry H., Cari Countryman e Thomas O. Baldwin. "Nucleotide sequence of the luxR and luxI genes and structure of the primary regulatory region of the lux regulon of Vibrio fischeri ATCC 7744". Biochemistry 27, n. 2 (26 gennaio 1988): 837–42. http://dx.doi.org/10.1021/bi00402a052.

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47

Shadel, G. S., e T. O. Baldwin. "The Vibrio fischeri LuxR protein is capable of bidirectional stimulation of transcription and both positive and negative regulation of the luxR gene." Journal of Bacteriology 173, n. 2 (1991): 568–74. http://dx.doi.org/10.1128/jb.173.2.568-574.1991.

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48

Koch, B., T. Liljefors, T. Persson, J. Nielsen, S. Kjelleberg e M. Givskov. "The LuxR receptor: the sites of interaction with quorum-sensing signals and inhibitors". Microbiology 151, n. 11 (1 novembre 2005): 3589–602. http://dx.doi.org/10.1099/mic.0.27954-0.

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The function of LuxR homologues as quorum sensors is mediated by the binding of N-acyl-l-homoserine lactone (AHL) signal molecules to the N-terminal receptor site of the proteins. In this study, site-directed mutagenesis was carried out of the amino acid residues comprising the receptor site of LuxR from Vibrio fischeri, and the ability of the L42A, L42S, Y62F, W66F, D79N, W94D, V109D, V109T and M135A LuxR mutant proteins to activate green fluorescent protein expression from a PluxI promoter was measured. X-ray crystallographic studies of the LuxR homologue TraR indicated that residues Y53 and W57 form hydrogen bonds to the 1-carbonyl group and the ring carbonyl group, respectively, of the cognate AHL signal. Based on the activity and signal specificity of the LuxR mutant proteins, and on molecular modelling, a model is suggested in which Y62 (corresponding to Y53 in TraR) forms a hydrogen bond with the ring carbonyl group rather than the 1-carbonyl group, while W66 (corresponding to W57 in TraR) forms a hydrogen bond to the 1-carbonyl group. This flips the position of the acyl side chain in the LuxR/signal molecule complex compared to the TraR/signal molecule complex. Halogenated furanones from the marine alga Delisea pulchra and the synthetic signal analogue N-(sulfanylacetyl)-l-homoserine lactone can block quorum sensing. The LuxR mutant proteins were insensitive to inhibition by N-(propylsulfanylacetyl)-l-homoserine lactone. In contrast, the mutations had only a minor effect on the sensitivity of the proteins to halogenated furanones, and the data strongly suggest that these compounds do not compete in a ‘classic’ way with N-3-oxohexanoyl-l-homoserine lactone for the binding site. Based on modelling and experimental data it is suggested that these compounds bind in a non-agonist fashion.

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49

Adar, Y. Y., M. Simaan e S. Ulitzur. "Formation of the LuxR protein in the Vibrio fischeri lux system is controlled by HtpR through the GroESL proteins." Journal of Bacteriology 174, n. 22 (1992): 7138–43. http://dx.doi.org/10.1128/jb.174.22.7138-7143.1992.

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50

Rui, Haopeng. "Role of Alkaline Serine Protease, Asp, in Vibrio alginolyticus Virulence and Regulation of Its Expression by LuxO-LuxR Regulatory System". Journal of Microbiology and Biotechnology 19, n. 5 (28 maggio 2009): 431–38. http://dx.doi.org/10.4014/jmb.0807.404.

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