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1.
Chemosphere ; 247: 125953, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32069724

RESUMO

In conventional membrane bioreactor (MBR) treatment systems, Gram-negative bacterial population appears to be always outnumbered Gram-positive community. Thereby, acyl homoserine lactones (AHLs), major signaling molecules utilized by Gram-negative bacteria, have been targeted for biofouling control in quorum quenching (QQ) based studies. This study investigated the impact of AHL and autoinducer-2 (AI-2)-degrading QQ consortium on the selective accumulation of microbial communities in a QQ MBR (MBR-QQb). The results show that addition of the QQ consortium (in the form of beads) increased the filtration time of MBR-QQb by 3.5 times. The distribution of mixed liquor extracellular polymeric substances (EPS), especially the tightly bound (TB) proteinous EPS and the floc size were strongly affected by the QQ activity, and the endless 'battle' between QQ and quorum sensing (QS). More importantly, QQ induced the significant suppression of Gram-negative bacterial community. The average abundance of Gram-positive bacteria at the genus level in the biocake of MBR-QQb (51%) was significantly higher than that of the control MBR (11%) and the MBR with vacant beads (28%). These findings suggest that an unintended condition is created to favor the growth of Gram-positive bacteria in QQ MBRs, resulting in a distinct microbial social network in both bulk sludge and biocake.


Assuntos
Reatores Biológicos/microbiologia , Membranas Artificiais , Microbiota , Percepção de Quorum , Acil-Butirolactonas/metabolismo , Incrustação Biológica , Bactérias Gram-Positivas/crescimento & desenvolvimento , Esgotos/microbiologia
2.
J Med Microbiol ; 69(3): 361-371, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32043956

RESUMO

Pseudomonas chlororaphis isolates have been studied intensively for their beneficial traits. P. chlororaphis species function as probiotics in plants and fish, offering plants protection against microbes, nematodes and insects. In this review, we discuss the classification of P. chlororaphis isolates within four subspecies; the shared traits include the production of coloured antimicrobial phenazines, high sequence identity between housekeeping genes and similar cellular fatty acid composition. The direct antimicrobial, insecticidal and nematocidal effects of P. chlororaphis isolates are correlated with known metabolites. Other metabolites prime the plants for stress tolerance and participate in microbial cell signalling events and biofilm formation among other things. Formulations of P. chlororaphis isolates and their metabolites are currently being commercialized for agricultural use.


Assuntos
Anti-Infecciosos/metabolismo , Biofilmes/crescimento & desenvolvimento , Fenazinas/metabolismo , Plantas/microbiologia , Probióticos , Pseudomonas chlororaphis/classificação , Acil-Butirolactonas/metabolismo , Agricultura , Antinematódeos/metabolismo , Cianeto de Hidrogênio/metabolismo , Inseticidas/metabolismo , Fenótipo , Plantas/imunologia , Pseudomonas chlororaphis/química , Pseudomonas chlororaphis/crescimento & desenvolvimento , Pseudomonas chlororaphis/fisiologia , Pirrolnitrina/metabolismo , Resorcinóis/metabolismo , Sideróforos/metabolismo , Compostos Orgânicos Voláteis/metabolismo
3.
J Agric Food Chem ; 68(8): 2516-2527, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32050067

RESUMO

In the Gram-negative bacterium Aeromonas hydrophila, N-acyl homoserine lactone (AHL)-mediated quorum sensing (QS) influences pathogenicity, protein secretion, and motility. However, the catalytic mechanism of AHL biosynthesis and the structural basis and substrate specificity for AhyI members remain unclear. In this study, we cloned the ahyI gene from the isolate A. hydrophila HX-3, and the overexpressed AhyI protein was confirmed to produce six types of AHLs by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis, contrasting with previous reports that AhyI only produces N-butanoyl-l-homoserine lactone (C4-HSL) and N-hexanoyl-l-homoserine lactone (C6-HSL). The results of an in vitro biosynthetic assay showed that purified AhyI can catalyze the formation of C4-HSL using S-adenosyl-l-methionine (SAM) and butyryl-acyl carrier protein (ACP) as substrates and indicated that the fatty acyl substrate used in AhyI-mediated AHL synthesis is derived from acyl-ACP rather than acyl-CoA. The kinetic data of AhyI using butyryl-ACP as an acyl substrate indicated that the catalytic efficiency of the A. hydrophila HX-3 AhyI enzyme is within an order of magnitude compared to other LuxI homologues. In this study, for the first time, the tertiary structural modeling results of AhyI and those of molecular docking and structural and functional analyses showed the importance of several crucial residues, as well as the secondary structure with respect to acylation. A Phe125-Phe152 clamp grasps the terminal methyl group to assist in stabilizing the long acyl chains in a putative binding pocket. The stacking interactions within a strong hydrophobic environment, a hydrogen-bonding network, and a ß bulge presumably stabilize the ACP acyl chain for the attack of the SAM α-amine toward the thioester carbon, offering a relatively reasonable explanation for how AhyI can synthesize AHLs with diverse acyl-chain lengths. Moreover, Trp34 participates in forming the binding pocket for C4-ACP and becomes ordered upon SAM binding, providing a good basis for catalysis. The novel finding that AhyI can produce both short- and long-chain AHLs enhances current knowledge regarding the variety of AHLs produced by this enzyme. These structural data are expected to serve as a molecular rationale for AHL synthesis by AhyI.


Assuntos
Aeromonas hydrophila/enzimologia , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , 4-Butirolactona/análogos & derivados , 4-Butirolactona/metabolismo , Acil-Butirolactonas/química , Acil-Butirolactonas/metabolismo , Aeromonas hydrophila/química , Aeromonas hydrophila/genética , Aeromonas hydrophila/metabolismo , Proteínas de Bactérias/genética , S-Adenosilmetionina/metabolismo , Especificidade por Substrato , Espectrometria de Massas em Tandem
4.
Syst Appl Microbiol ; 43(1): 126018, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31733924

RESUMO

Strain MOLA 401T was isolated from marine waters in the southwest lagoon of New Caledonia and was shown previously to produce an unusual diversity of quorum sensing signaling molecules. This strain was Gram-negative, formed non-motile cocci and colonies were caramel. Optimum growth conditions were 30°C, pH 8 and 3% NaCl (w/v). Based on 16S rRNA gene sequence analysis, this strain was found to be closely related to Pseudomaribius aestuariivivens NBRC 113039T (96.9% of similarity), Maribius pontilimi DSM 104950T (96.4% of similarity) and Palleronia marisminoris LMG 22959T (96.3% of similarity), belonging to the Roseobacter group within the family Rhodobacteraceae. As its closest relatives, strain MOLA 401T is able to form a biofilm on polystyrene, supporting the view of Roseobacter group strains as prolific surface colonizers. An in-depth genomic study allowed us to affiliate strain MOLA 401T as a new species of genus Palleronia and to reaffiliate some of its closest relatives in this genus. Consequently, we describe strain MOLA 401T (DSM 106827T=CIP 111607T=BBCC 401T) for which we propose the name Palleronia rufa sp. nov. We also propose to emend the description of the genus Palleronia and to reclassify Maribius and Hwanghaeicola species as Palleronia species.


Assuntos
Acil-Butirolactonas/metabolismo , Biofilmes/crescimento & desenvolvimento , Rhodobacteraceae/classificação , Rhodobacteraceae/fisiologia , Proteínas de Bactérias/genética , DNA Bacteriano/genética , Genes Essenciais/genética , Genoma Bacteriano/genética , Nova Caledônia , Filogenia , Percepção de Quorum , RNA Ribossômico 16S/genética , Rhodobacteraceae/química , Rhodobacteraceae/citologia , Roseobacter/química , Roseobacter/classificação , Roseobacter/citologia , Roseobacter/fisiologia , Água do Mar/microbiologia , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie
5.
J Appl Microbiol ; 128(1): 15-27, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31102552

RESUMO

Acinetobacter baumannii causes several nosocomial infections and poses major threat when it is multidrug resistant. Even pan drug-resistant strains have been reported in some countries. The intensive care unit (ICU) mortality rate ranged from 45.6% to 60.9% and it is as high as 84.3% when ventilator-associated pneumonia was caused by XDR (extensively drug resistant) A. baumannii. Acinetobacter baumannii constituted 9.4% of all Gram-negative organisms throughout the hospital and 22.6% in the ICUs according to a study carried out in an Indian hospital. One of the major factors contributing to drug resistance in A. baumannii infections is biofilm development. Quorum sensing (QS) facilitates biofilm formation and therefore the search for 'quorum quenchers' has increased recently. Such compounds are expected to inhibit biofilm formation and hence reduce/prevent development of drug resistance in the bacteria. Some of these compounds also target synthesis of some virulence factors (VF). Several candidate drugs have been identified and are at various stages of drug development. Since quorum quenching, inhibition of biofilm formation and inhibition of VF synthesis do not pose any threat to the DNA replication and cell division of the bacteria, chances of resistance development to such compounds is presumably rare. Thus, these compounds ideally qualify as adjunct therapeutics and could be administered along with an antibiotic to reduce chances of resistance development and also to increase the effectiveness of antimicrobial therapy. This review describes the state-of-art in QS process in Gram-negative bacteria in general and in A. baumannii in particular. This article elaborates the nature of QS mediators, their characteristics, and the methods for their detection and quantification. Various potential sites in the QS pathway have been highlighted as drug targets and the candidate quorum quenchers which inhibit the mediator's synthesis or function are enlisted.


Assuntos
Infecções por Acinetobacter/microbiologia , Acinetobacter baumannii/fisiologia , Percepção de Quorum , Infecções por Acinetobacter/tratamento farmacológico , Acinetobacter baumannii/efeitos dos fármacos , Acinetobacter baumannii/patogenicidade , Acil-Butirolactonas/metabolismo , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Proteínas de Bactérias/metabolismo , Biofilmes/efeitos dos fármacos , Biofilmes/crescimento & desenvolvimento , Desenvolvimento de Medicamentos , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Farmacorresistência Bacteriana Múltipla/genética , Percepção de Quorum/efeitos dos fármacos , Fatores de Virulência/metabolismo
6.
Sci Total Environ ; 698: 134236, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31493577

RESUMO

The widespread emergence of antibiotic resistance genes (ARGs) in drinking water systems endangers human health, and may be exacerbated by their horizontal gene transfer (HGT) among microbiota. In our previous study, Quorum sensing (QS) molecules produced by bacteria from biological activated carbon (BAC) biofilms were demonstrated to influence the transfer efficiency of a model conjugative plasmid, here RP4. In this study, we further explored the effect and mechanism of QS on conjugation transfer. The results revealed that Acyl-homoserine lactones producing (AHL-producing) bacteria isolated from BAC biofilm play a role in the propagation of ARGs. We selected several quorum sensing inhibitors (QSIs) to study their effects on AHL-producing bacteria, including the formation of biofilm and the regulating effect on conjugation transfer. In addition, the possible molecular mechanisms for AHLs that promote conjugative transfer were attributable to enhancing the mRNA expression, which involved altered expressions of conjugation-related genes. We also found that QSIs could inhibit conjugative transfer by downregulating the conjugation-relevant genes. We believe that this is the first insightful exploration of the mechanism by which AHLs will facilitate and QSIs will inhibit the conjugative transfer of ARGs. These results provide creative insight into ARG pollution control that involves blocking QS during BAC treatment in drinking water systems.


Assuntos
Acil-Butirolactonas/metabolismo , Biofilmes , Percepção de Quorum , Carvão Vegetal , Água Potável/microbiologia , Transferência Genética Horizontal , Plasmídeos
7.
Microbes Environ ; 34(4): 429-435, 2019 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-31666459

RESUMO

The plant pathogen Pectobacterium carotovorum subsp. carotovorum (Pcc) regulates the expression of virulence factors by N-acylhomoserine lactone (AHL)-mediated quorum sensing. The LuxI family protein, ExpI, catalyzes AHL biosynthesis in Pcc. The structure of the predominant AHL produced by ExpI differs among Pcc strains, which may be divided into two quorum-sensing classes (QS classes) based on the AHL produced. In the present study, AHL produced by 282 Pcc strains were extracted and identified by LC-MS/MS. Seventy Pcc strains produced N-(3-oxooctanoyl)-l-homoserine lactone (3-oxo-C8-HSL) as the predominant AHL and were categorized into QS class I. Two hundred Pcc strains produced N-(3-oxohexanoyl)-l-homoserine lactone (3-oxo-C6-HSL) as the predominant AHL, and were categorized into QS class II-1. Twelve Pcc strains produced only small amounts of 3-oxo-C6-HSL, and were categorized into QS class II-2. The phylogenetic analysis revealed that the amino acid sequences of ExpI may be divided into two major clades (I and II). The Pcc strains categorized into ExpI clades I and II entirely matched QS classes I and II, respectively. A multiple alignment analysis demonstrated that only 6 amino acid substitutions were observed among ExpI from QS classes II-1 and II-2. Furthermore, many amino acid substitutions between QS classes I and II were concentrated at the C-terminal region. These amino acid substitutions are assumed to cause significant reductions in 3-oxo-C6-HSL in QS class II-2 or affect the substrate specificity of ExpI between QS classes I and II.


Assuntos
Acil-Butirolactonas/metabolismo , Variação Genética , Pectobacterium carotovorum/genética , Pectobacterium carotovorum/metabolismo , Doenças das Plantas/microbiologia , 4-Butirolactona/análogos & derivados , 4-Butirolactona/química , 4-Butirolactona/metabolismo , Acil-Butirolactonas/química , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Homosserina/análogos & derivados , Homosserina/química , Homosserina/metabolismo , Pectobacterium carotovorum/classificação , Filogenia , Percepção de Quorum
8.
Int J Mol Sci ; 20(22)2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31717364

RESUMO

Numerous gram-negative phytopathogenic and zoopathogenic bacteria utilise acylated homoserine lactone (AHL) in communication systems, referred to as quorum sensing (QS), for induction of virulence factors and biofilm development. This phenomenon positions AHL-mediated QS as an attractive target for anti-infective therapy. This review focused on the most significant groups of plant-derived QS inhibitors and well-studied individual compounds for which in silico, in vitro and in vivo studies provide substantial knowledge about their modes of anti-QS activity. The current data about sulfur-containing compounds, monoterpenes and monoterpenoids, phenylpropanoids, benzoic acid derivatives, diarylheptanoids, coumarins, flavonoids and tannins were summarized; their plant sources, anti-QS effects and bioactivity mechanisms have also been summarized and discussed. Three variants of plant-derived molecules anti-QS strategies are proposed: (i) specific, via binding with LuxI-type AHL synthases and/or LuxR-type AHL receptor proteins, which have been shown for terpenes (carvacrol and l-carvone), phenylpropanoids (cinnamaldehyde and eugenol), flavonoid quercetin and ellagitannins; (ii) non-specific, by affecting the QS-related intracellular regulatory pathways by lowering regulatory small RNA expression (sulphur-containing compounds ajoene and iberin) or c-di-GMP metabolism reduction (coumarin); and (iii) indirect, via alteration of metabolic pathways involved in QS-dependent processes (vanillic acid and curcumin).


Assuntos
Acil-Butirolactonas/metabolismo , Bactérias/metabolismo , Plantas/química , Percepção de Quorum
9.
Appl Microbiol Biotechnol ; 103(21-22): 9169-9180, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31673743

RESUMO

Pseudomonas stutzeri strain XL-2 exhibited significant performance on biofilm formation. Extracellular polymeric substances (EPS) secreted by strain XL-2 were characterized by colorimetry and Fourier transform infrared (FT-IR) spectroscopy. The biofilm growth showed a strong positive correlation (rP=0.96, P<0.01) to extracellular protein content, but no correlation to exopolysaccharide content. Hydrolyzing the biofilm with proteinase K caused a significant decrease in biofilm growth (t=3.7, P<0.05), whereas the changes in biofilm growth were not significant when the biofilm was hydrolyzed by α-amylase and ß-amylase, implying that proteins rather than polysaccharides played the dominant role in biofilm formation. More specifically, confocal laser scanning microscopy (CLSM) revealed that the extracellular proteins were tightly bound to the cells, resulting in the cells with EPS presenting more biofilm promotion protein secondary structures, such as three-turn helices, ß-sheet, and α-helices, than cells without EPS. Both bio-assays and quantitative analysis demonstrated that strain XL-2 produced signal molecules of N-acylhomoserine lactones (AHLs) during biofilm formation process. The concentrations of C6-HLS and C6-oxo-HLS were both significantly positively correlated with protein contents (P<0.05). Dosing exogenous C6-HLS and C6-oxo-HLS also resulted in the increase in protein content. Therefore, it was speculated that C6-HLS and C6-oxo-HLS released by strain XL-2 could up-regulate the secretion of proteins in EPS, and thus promote the formation of biofilm.


Assuntos
Biofilmes/crescimento & desenvolvimento , Matriz Extracelular de Substâncias Poliméricas/microbiologia , Pseudomonas stutzeri/crescimento & desenvolvimento , Pseudomonas stutzeri/metabolismo , Acil-Butirolactonas/metabolismo , Microscopia Confocal , Espectroscopia de Infravermelho com Transformada de Fourier , alfa-Amilases/metabolismo , beta-Amilase/metabolismo
10.
ACS Chem Biol ; 14(10): 2305-2314, 2019 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-31545595

RESUMO

Virulence in the Gram-negative pathogen Pseudomonas aeruginosa relies in part on the efficient functioning of two LuxI/R dependent quorum sensing (QS) cascades, namely, the LasI/R and RhlI/R systems that generate and respond to N-(3-oxo)-dodecanoyl-l-homoserine lactone and N-butyryl-l-homoserine lactone, respectively. The two acyl homoserine lactone (AHL) synthases, LasI and RhlI, use 3-oxododecanoyl-ACP and butyryl-ACP, respectively, as the acyl-substrates to generate the corresponding autoinducer signals for the bacterium. Although AHL synthases represent excellent targets for developing QS modulators in P. aeruginosa, and in other related bacteria, the identification of potent and signal synthase specific inhibitors has represented a significant technical challenge. In the current study, we sought to test the utility of AHL analogs as potential modulators of an AHL synthase and selected RhlI in P. aeruginosa as an initial target. We systematically varied the chemical functionalities of the AHL headgroup, acyl chain tail, and head-to-tail linkage to construct a small library of signal analogs and evaluated them for RhlI modulatory activity. Although the native N-butyryl-l-homoserine lactone did not inhibit RhlI, we discovered that several of our long-chain, unsubstituted acyl-d-homoserine lactones and acyl-d-homocysteine thiolactones inhibited while a few of the 3-oxoacyl-chain counterparts activated the enzyme. Additional mechanistic investigations with acyl-substrate analogs and docking experiments with AHL analogs revealed two distinct inhibitor and activator binding pockets in the enzyme. This study provides the first evidence of the yet untapped potential of AHL analogs as signal synthase modulators of QS pathways.


Assuntos
Acil-Butirolactonas/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Ligases/antagonistas & inibidores , Pseudomonas aeruginosa/efeitos dos fármacos , Percepção de Quorum/efeitos dos fármacos , Fatores de Transcrição/antagonistas & inibidores , Acil-Butirolactonas/química , Acil-Butirolactonas/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Inibidores Enzimáticos/química , Inibidores Enzimáticos/metabolismo , Ligases/química , Ligases/metabolismo , Simulação de Acoplamento Molecular , Estrutura Molecular , Estudo de Prova de Conceito , Ligação Proteica , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo
11.
Appl Microbiol Biotechnol ; 103(21-22): 9181-9189, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31468088

RESUMO

Aerobic granule is widely recognized as a promising biological wastewater treatment technique. Acyl-homoserine lactone (AHL)-mediated quorum sensing and quenching are reported to be involved in the formation of aerobic granules. However, little is known about how environmental factors affect the AHL-producing and AHL-quenching communities and their activities in aerobic granules. Therefore, in this work, the bacterial community of aerobic granules was explored and the impacts of substrate, electron acceptor, sludge concentration, pH, and temperature on the AHL-related communities and activities of aerobic granules were examined. These factors were found to affect the AHL-related activities, and thereby change the AHL level. The AHL-producing activities were observed to be more sensitive to the variation of these factors than the AHL-quenching activities. These findings help to establish the links between environmental factors and AHL-related activities and thus provide useful guides for the operation of aerobic granule systems.


Assuntos
Acil-Butirolactonas/metabolismo , Bactérias/metabolismo , Esgotos/microbiologia , Águas Residuárias/microbiologia , Aerobiose , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Reatores Biológicos/microbiologia , Percepção de Quorum
12.
Int J Biol Macromol ; 140: 368-376, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31425763

RESUMO

Quorum Quenching (QQ) enzymes can be used to prevent bacterial antibiotic resistance by degradation of Quorum Sensing (QS) signaling molecules, for example N-acyl homoserine lactones (AHLs). This paper is aimed at the in silico investigation of the possible combinations of hexahistidine-tagged organophosphorus hydrolase (His6-OPH) with antimicrobial peptides (AMPs) to improve the enzyme activity and, promisingly, stability. This shall help creating a nanosized QQ preparation capable to hydrolyze different AHLs and possessing an antimicrobial activity. To achieve this, binding of AMPs and His6-OPH was simulated by molecular docking, and various interaction parameters (affinity, charge, contact area, etc.) of the generated models were studied. Both anionic and cationic polypeptides were shown to bind to His6-OPH with negligible effect of their charge, that significantly deviates from the charge-to-charge interaction concept. The (nano)complexes of His6-OPH with Indolicidin and Temporin A appear to have the most balanced characteristics which were issued experimentally also.


Assuntos
Antibacterianos/química , Arildialquilfosfatase/química , Histidina/química , Simulação de Acoplamento Molecular , Oligopeptídeos/química , Peptídeos/química , Polieletrólitos/química , Percepção de Quorum , Acil-Butirolactonas/metabolismo , Peptídeos Catiônicos Antimicrobianos/química , Hidrólise , Modelos Moleculares , Nanocompostos/química , Proteínas/química
13.
Res Microbiol ; 170(6-7): 296-299, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31279087

RESUMO

Quorum sensing (QS) is a molecular communication system that bacteria use to harmonize the regulation of genes in a cell density-dependent manner. In proteobacteria, QS is involved, among others, in virulence, biofilm formation or CRISPR-Cas gene regulation. Here, we report for the first time the effect of a QS-interfering enzyme to alter the regulation of CRISPR-Cas systems in model and clinical strains of Pseudomonas aeruginosa, as well as in the marine bacterium Chromobacterium violaceum CV12472. The expression of CRISPR-Cas genes decreased in most cases suggesting that enzymatic disruption of QS is promising for modulating phage-bacteria interactions.


Assuntos
Acil-Butirolactonas/metabolismo , Sistemas CRISPR-Cas/genética , Chromobacterium/genética , Regulação Bacteriana da Expressão Gênica/genética , Pseudomonas aeruginosa/genética , Percepção de Quorum/genética , Bacteriófagos/genética , Bacteriófagos/crescimento & desenvolvimento , Biofilmes/crescimento & desenvolvimento , Chromobacterium/isolamento & purificação , Chromobacterium/metabolismo , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Humanos , Pseudomonas aeruginosa/isolamento & purificação , Pseudomonas aeruginosa/metabolismo
14.
Microbiology ; 165(12): 1265-1281, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31264956

RESUMO

Quorum sensing (QS) refers to chemical signalling between micro-organisms and defines a social concord among them. Once a threshold of signal is accumulated, certain virulent traits are regulated within bacteria in response to the surrounding environment. These virulence traits are known to contribute in the pathogenicity of bacterial diseases. To prevent the activation of virulence factors, QS is inhibited in different ways through a strategy known as quorum quenching. Various types of quorum-quenching strategies have already been used and characterized, as discussed in this review. The phenomenon of quorum quenching has long been considered as an alternative therapy to circumvent the ill-effects of the overuse of antibiotics. Considering the need to compare and evaluate various strategies, selected quorum-quenching paradigms are detailed along with their pros and cons in this review. A rationale has been drawn between naturally evolved quorum-quenching strategies and synthetically modified approaches adopted to abrogate QS.


Assuntos
Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Percepção de Quorum/efeitos dos fármacos , Acil-Butirolactonas/química , Acil-Butirolactonas/metabolismo , Antibacterianos/biossíntese , Antibacterianos/síntese química , Antibacterianos/uso terapêutico , Bactérias/enzimologia , Bactérias/patogenicidade , Infecções Bacterianas/tratamento farmacológico , Infecções Bacterianas/microbiologia , Biofilmes/efeitos dos fármacos , Farmacorresistência Bacteriana , Humanos , Transdução de Sinais/efeitos dos fármacos , Virulência/efeitos dos fármacos
15.
Res Microbiol ; 170(6-7): 243-255, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31325485

RESUMO

Bacteria usually produce, release and detect quorum sensing (QS)-based signal molecules, and successively orchestrate gene expression in respond to environmental changes. Pseudoalteromonas are typical marine bacteria, but knowledge on their QS systems is extremely fragmentary. In this study, genome sequencing of Pseudoalteromonas sp. R3 was performed. Accordingly, a QS working model including three sets of hierarchically organized QS systems was proposed in strain R3. Among them, the typical LuxI/R-type QS system using acyl-homoserine lactones (AHLs) as signal molecules was characterized. Sequence similarity analysis indicated luxI encoding AHLs synthase is novel. The luxR encoding AHLs receptor is directly adjacent to luxI downstream. Notably, mutagenesis demonstrated LuxI and LuxR affect each other at transcriptional level, and both control the AHLs formation. Interestingly, it was found that LuxI/R-type QS system positively involves resistance to streptomycin. Thin-layer chromatography analysis showed strain R3 can produce 3-OH-C6-HSL and C8-HSL, which was supported by heterologous expression of LuxI in Escherichia coli. Sequence alignment analysis indicated that the N-terminal region of LuxI is more conservative than the C-terminal region, revealing the importance of N-terminal region in AHLs synthesis. The obtained findings enrich our knowledge on LuxI/R-type QS system in Pseudoalteromonas and its regulation on adaptation to marine environments.


Assuntos
Acil-Butirolactonas/metabolismo , Proteínas de Bactérias/genética , Farmacorresistência Bacteriana/genética , Pseudoalteromonas/genética , Percepção de Quorum/genética , Proteínas Repressoras/genética , Transativadores/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Antibacterianos/farmacologia , Sequência de Bases , Regulação Bacteriana da Expressão Gênica/genética , Genoma Bacteriano/genética , Pseudoalteromonas/efeitos dos fármacos , Pseudoalteromonas/fisiologia , Alinhamento de Sequência , Transdução de Sinais/genética , Estreptomicina/farmacologia , Sequenciamento Completo do Genoma
16.
Microbiol Res ; 223-225: 72-78, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31178054

RESUMO

Pseudomonas syringae pathovars are known to produce N-acyl-homoserine lactones (AHL) as quorum-sensing molecules. However, many isolates, including P. syringae pv. tomato DC3000 (PtoDC3000), do not produce them. In P. syringae, psyI, which encodes an AHL synthase, and psyR, which encodes the transcription factor PsyR required for activation of psyI, are convergently transcribed. In P. amygdali pv. tabaci 6605 (Pta6605), there is one nucleotide between the stop codons of both psyI and psyR. However, the canonical stop codon for psyI in PtoDC3000 was converted to the cysteine codon by one nucleotide deletion, and 23 additional amino acids extended it to a C-terminal end. This resulted in overlapping of the open reading frame (ORF) for psyI and psyR. On the other hand, stop codons in the psyR ORF of P. syringae 7 isolates, including pv. phaseolicola and pv. glycinea, were found. These results indicate that many pathovars of P. syringae have genetically lost AHL production ability by the mutation of their responsible genes. To examine whether PtoDC3000 modulates the gene expression profile in a population-dependent manner, we carried out microarray analysis using RNAs prepared from low- and high-density cells. We found the expressions of rsmX and rsmY remarkably activated in high-density cells. The activated expressions of rsmX and rsmY were confirmed by Northern blot hybridization, but these expressions were abolished in a ΔgacA mutant of Pta6605. These results indicate that regardless of the ability to produce AHL, P. syringae regulates expression of the small noncoding RNAs rsmX/Y by currently unknown quorum-sensing molecules.


Assuntos
Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos/genética , Pseudomonas syringae/genética , Pseudomonas syringae/metabolismo , Pequeno RNA não Traduzido/genética , Acil-Butirolactonas/metabolismo , Doenças das Plantas/microbiologia , Pseudomonas syringae/enzimologia , Pseudomonas syringae/patogenicidade , Percepção de Quorum/genética , Análise de Sequência de DNA , Fatores de Transcrição/genética , Transcriptoma , Virulência/genética
17.
Environ Int ; 130: 104946, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31252169

RESUMO

Aerobic granular sludge (AGS) is promising in wastewater treatment. However, the formation and existence of AGS under low organic loading rate (OLR) is still not fully understood due to a knowledge gap in the variations and correlations of N-acyl-homoserine lactones (AHLs), the microbial community, extracellular polymeric substances (EPS) and other physiochemical granule properties. This study comprehensively investigated the AHL-mediated quorum sensing (QS) and microbial community characters in the AGS fed with ammonium-rich wastewater under a low OLR of 0.15 kg COD (m3 d)-1. The results showed that the AGS appeared within 90 days, and the size of mature granules was over 700 µm with strong settleability and ammonium removal performance. More tightly-bound extracellular polysaccharide and tightly-bound extracelluar protein were produced in the larger AGS. C10-HSL and C12-HSL gradually became dominant in sludge, and short-chain AHLs dominated in water. EPS producers and autotrophic nitrifiers were successfully retained in the AGS under low OLR. AHL-mediated QS utilized C10-HSL, C12-HSL and 3OC6-HSL as the critical AHLs to regulate the TB-EPS in aerobic granulation, and autotrophic nitrifiers may perform interspecific communication with C10-HSL. The correlations of bacterial genera with AGS properties and AHLs were complex due to the dynamic fluctuations of microbial composition and other variable factors in the mixed-culture system. These findings confirmed the participation of AHL-mediated QS in the regulation of microbial community characters and AGS properties under low OLR, which may provide guidance for the operation of AGS systems under low OLR from a microbiological viewpoint.


Assuntos
Acil-Butirolactonas/metabolismo , Reatores Biológicos , Microbiota , Percepção de Quorum , Esgotos/microbiologia , Bactérias/metabolismo
18.
Chemosphere ; 234: 310-317, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31228833

RESUMO

Quorum sensing (QS) has been thoroughly investigated during initial biofilm formation stages, while the role of QS in mature biofilms has received little research attention. This study assessed QS in 22 biofilm samples from full-scale wastewater treatment plants in China. Results showed that the concentration of acyl-homoserine lactones (AHLs) in various biofilm bound forms, ranged from 15.63 to 609.76 ng/g. The highest concentration of AHLs was found in the tightly bound biofilm fraction, while the lowest concentrations were observed in the surface biofilm fraction. Environmental variables, C/N ratio and temperature, were found to be significant factors influencing biofilm AHL distribution (p < 0.01). Higher C/N ratios (ranging from 3 to 12) and low temperatures contributed to the higher concentration of AHLs in biofilms. Dominant AHLs (C10-HSL and C12-HSL) were significantly associated with biofilm activity (R2 = 0.98/0.97, p < 0.05), with the tightly bound biofilm fraction (TB-biofilm) presenting the highest activity (ATP concentration). Biofilm aging and re-formation processes were more active in the surface biofilm layer (S-biofilm), while the stable structure of the TB-biofilm layer which is attached to the surface of bio-carriers ensures high biofilm activity. This study furthers our understanding of the roles of AHLs in the regulation of mature biofilm activities.


Assuntos
Acil-Butirolactonas/análise , Biofilmes , Percepção de Quorum , Águas Residuárias/microbiologia , Purificação da Água/métodos , Acil-Butirolactonas/metabolismo , Carbono , China , Nitrogênio , Temperatura
19.
Mol Microbiol ; 112(2): 678-698, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31124196

RESUMO

The genome of Sinorhizobium meliloti, a model for studying plant-bacteria symbiosis, contains eight genes coding for LuxR-like proteins. Two of these, SinR and ExpR, are essential for quorum sensing (QS). Roles and regulation surrounding the others are mostly unknown. Here, we reveal the DNA recognition sequence and regulon of the LuxR-like protein SMc00877. Unlike ExpR, which uses the long-chain acyl homoserine lactones (AHLs) as inducers, SMc00877 functioned independently of AHLs and was even functional in Escherichia coli. A target of SMc00877 is SinR, the major regulator of AHL production in S. meliloti. Disruption of SMc00877 decreased AHL production. A weaker production of AHLs resulted in smaller microcolonies, starting from single cells, and delayed AHL-dependent regulation. SMc00877 was expressed only in growing cells in the presence of replete nutrients. Therefore, we renamed it NurR (nutrient sensitive LuxR-like regulator). We traced this nutrient-sensitive expression to transcription control by the DNA replication initiation factor, DnaA, which is essential for growth. These results indicate that NurR has a role in modulating the threshold of QS activation according to growth. We propose growth behavior as an additional prerequisite to population density for the activation of QS in S. meliloti.


Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Ligação a DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Percepção de Quorum , Proteínas Repressoras/metabolismo , Sinorhizobium meliloti/fisiologia , Transativadores/metabolismo , Acil-Butirolactonas/metabolismo , Proteínas de Bactérias/genética , Replicação do DNA , Proteínas de Ligação a DNA/genética , Regulon , Proteínas Repressoras/genética , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/crescimento & desenvolvimento , Transativadores/genética
20.
Science ; 364(6436): 178-181, 2019 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-30975887

RESUMO

In plants, cell-surface immune receptors sense molecular non-self-signatures. Lipid A of Gram-negative bacterial lipopolysaccharide is considered such a non-self-signature. The receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (LORE) mediates plant immune responses to Pseudomonas and Xanthomonas but not enterobacterial lipid A or lipopolysaccharide preparations. Here, we demonstrate that synthetic and bacterial lipopolysaccharide-copurified medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) metabolites elicit LORE-dependent immunity. The mc-3-OH-FAs are sensed in a chain length- and hydroxylation-specific manner, with free (R)-3-hydroxydecanoic acid [(R)-3-OH-C10:0] representing the strongest immune elicitor. By contrast, bacterial compounds comprising mc-3-OH-acyl building blocks but devoid of free mc-3-OH-FAs-including lipid A or lipopolysaccharide, rhamnolipids, lipopeptides, and acyl-homoserine-lactones-do not trigger LORE-dependent responses. Hence, plants sense low-complexity bacterial metabolites to trigger immune responses.


Assuntos
Arabidopsis/imunologia , Arabidopsis/microbiologia , Ácidos Decanoicos/metabolismo , Pseudomonas aeruginosa/metabolismo , Acil-Butirolactonas/metabolismo , Ácidos Decanoicos/química , Glicolipídeos/metabolismo , Lipídeo A/metabolismo , Lipopeptídeos/metabolismo
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