Physicochemical Processes of Biofilm Formation on The Surface of Structures in Water / 生物化学与生物物理进展

Microorganisms can form biofilms, complex, heterogeneous, multicellular communities that adhere to surfaces. Biofilm formation on the surface of structures in water will accelerate structures’ corrosion, seriously affect their service efficiency and life, and significantly impact the growth of animals, plants, and human life. Hence, clarifying the mechanism of biofilm formation contributes to developing new strategies to control biofilm formation on surface and then reduce infections, biofouling, and contaminations. Biofilm-targeting strategies include the regulation of established biofilms or the modulation of single-cell attachment. In most studies, physicochemical mechanism is frequently applied to explain the initial bacterial adhesion phenomena but rarely to explain other stages of biofilm formation. This review presents a five-step comprehensive description of the physicochemical process from film formation to biofilm maturation: (1) period of film formation; (2) period of bacterial adhesion; (3) period of extracellular-polymeric-substances (EPSs) membrane formation; (4) period of regulating biofilm by quorum sensing (QS); (5) period of biofilm maturation. We first clarify how the film formed by compound molecules affects the surface’s physicochemical properties and initial adhesion, summarizing many factors that affect bacterial adhesion. We then review the types of EPSs and signal molecules secreted by bacteria after irreversible adhesion, as well as their role and QS mechanism in biofilm maturation. Finally, we discuss how bacteria or microcolonies separate from the mature biofilm by physicochemical action and summarize the morphology and adhesion characterization methods after the biofilm matures. This review redefines the role of physicochemical in the whole process of biofilm formation and provides a theoretical basis for the prevention, removal, and utilization of biofilm and other related research fields.

A Rapid Method to Screen for Multi Drug Resistance (MDR) Trait in Clinical Isolates of Acinetobacter baumannii-Acyl Homoserine Lactone (AHL) Screening in CRAB and CSAB Isolates

Aims: Our proposal aimed to evaluate Acyl Homoserine Lactones (AHL) as a functional marker for Multi drug resistant (MDR) potential in clinical isolates of Acinetobacter baumannii. We investigated the AHL production potential of clinical isolates using a biosensor assay directly on a commonly used agar media. Place and Duration of Study: Department of Molecular Diagnostics and Biomarkers, Gleneagles Global Hospitals, Lakdikapul, Hyderabad-500004. Methodology: Antimicrobial drug sensitivity testing (AST) was performed on 72 clinical isolates of A. baumannii against two front-line antibiotics, Imipenem (10µg) and Meropenem (10µg), by Kirby-Bauer disk diffusion method. Production of long chain Acyl Homoserine lactone (AHLs) in the clinical isolates of A. baumannii was tested by cross streaking with the biosensor Chromobacterium violaceum mutant strain CV026 and Agrobacterium tumefaciens (NTL4pZLR4) by agar plate diffusion assay. Screening and identification of the quorum sensing mediator gene abaI was done by PCR to confirm its presence in all the 72 clinical isolates. Results: Out of the 72 clinical isolates, 58 were Carbapenem resistant Acinetobacter baumannii (CRAB) and 14 were Carbapenem sensitive Acinetobacter baumannii (CSAB) for AST by agar disc diffusion method. None of our isolates produced short chain AHLs whereas all the isolates could produce varying amounts of long chain AHLs. Genotypic confirmation of AHL gene was obtained by abaI gene PCR. Conclusion: Carbapenems are the front-line antibiotics used to treat gram negative bacterial infections in emergencies and in the critical care units of hospitals. Clinical isolates A. baumannii has innate resistance to several antibiotics due to various mechanisms, biofilms forming the first line of defense against antibiotics for the bacterium. Our study used AST to carbapenem as the leading marker for MDR, assuming the innate resistance of A. baumannii to other beta lactam antibiotics. Our study brought out certain important observations namely: a) All clinical isolates of A. baumannii produced Quorum Sensing signal molecules, the AHLs b) the clinical isolates of A. baumannii did not produce any short chain AHLs b) All the clinical isolates of A. baumannii produced long chain AHLs c) AHL production is not specific to carbapenem drug resistance because even CSAB isolates produced AHL d) AHL production is inherent to all clinical isolates of A. baumannii and it apparently indicates an underlying biofilm potential and MDR trait in these A. baumannii isolates. e) AHLs could be a universal marker for revealing MDR trait and biofilm potential in clinical microbiology AST profiling protocols.

Targeting Multidrug Resistant A. Baumannii to Evaluate Anti-Biofilm and Anti-Quorum Sensing Potential of Some Compounds

Background: The continuing search for new and novel antimicrobials for their potential as anti-biofilm and anti-quorum sensing agents has turned to many plant products possessing broad-spectrum anti-microbial activities. This potential has gained importance recently because the plant secondary metabolites exhibit anti-quorum sensing activity without interfering with the growth of the organism which thus would minimize the development of multidrug resistance. A. baumannii was the test organism in this study and we used carbapenem-resistant and sensitive clinical isolates. We have evaluated the anti-biofilm and anti-quorum sensing potential of two popular plant sources, namely mango seed kernels and guava leaves. Commonly used antimicrobial food preservative ?-Poly lysine was also evaluated for its anti-quorum sensing potential. Methods: Ethanolic extracts of these plant materials and ?-Poly lysine were tested for their Minimum Inhibitory Concentration (MIC) by disc diffusion method. The antibiofilm activity of the compounds was determined using a Microtitre Plate Test (MTP) and Scanning Electron Microscopy (SEM). The compounds were also evaluated for their anti-quorum sensing activity by the MTP method. Finally, these plant extracts were partially characterized by Gas Chromatography?Mass Spectrometry (GC?MS), and the major components were identified. Results: The MICs of GLE, MSKE and ?-Poly lysine against planktonic cells of the isolates were 60 µg/mL, 40 µg/mL, and 60 µg/mL respectively. The MTP test showed a significant inhibition by the natural extracts on the biofilm formation at sub?MIC concentrations. MSKE and ?-Poly lysine were the strong biofilm inhibitors that could hinder biofilm growth by over 60%-80% in both Carbapenem-Resistant Acinetobacter Baumannii (CRAB) and CSAB isolates. GLE exhibited a moderate effect on 54.5% of CRAB and 25% of CSAB isolates respectively. These results were confirmed by SEM where the biofilm has been reduced to individual cells scattered over the matrix surface. In addition, the relative number of bacteria in the biofilm matrix was significantly less compared to the untreated samples. A. baumannii cells after exposure have lost the biofilm integrity and the cells became flat and elongated. Inhibition of the quorum sensing signal molecule AHL, in terms of blue-green complex production, by MSKE was 47% in CRAB and 82% in CSAB isolates. However, GLE extract showed 42% and 69% inhibition of AHL production in CRAB and CSAB isolates respectively. Streptomycin and ?Poly lysine could inhibit the production of AHL by about 40% in CRAB and 80% in CSAB isolates. Conclusions: The present study demonstrated that MSKE, GLE ethanolic extracts, and ?-Poly lysine have strong potential as antibiofilm and anti?QS compounds which could be developed further as adjunct drugs for treating multi-drug resistant A. baumannii and for co-therapy-with-other-antibiotics-to-eliminate-development of resistance

Research progress of research on the effect of quorum-sensing system on periodontal pathogens / 口腔医学

@#Periodontitis is one of the most common oral diseases in humans. As the initiating factor of periodontitis, dental plaque bacteria, is the primary factor leading to periodontitis. Quorum-sensing system relies on quorum-sensing signaling molecules to regulate and strengthenthe communication between different kinds of bacteria, strengthen the communication between bacteria, and promote the occurrence and development of diseases. Quorum-sensing system also plays an important role in promoting the formation of dental plaque biofilm by dental plaque bacteria. In recent years, many studies have shown that quorum-sensing inhibitors can effectively attenuate quorum sensing between bacteria and inhibit and reduce the formation of plaque biofilms between bacteria and the expression of their virulence factors. In this paper, we will review the progress of research on the effects of quorum-sensing signaling molecules on periodontitis pathogens.

Mechanism of action of the microbial quorum-sensing system in the development of skin inflammation / 中华皮肤科杂志

Quorum-sensing system is a way of communication between cells that depends on changes in population density of microorganisms, and is closely associated with variety and pathogenicity of skin microbiota. The synthesis of virulence factors of Staphylococcus aureus ( S. aureus) is regulated by the accessory gene regulator (Agr) quorum-sensing system. Various skin commensals such as coagulase-negative Staphylococcus and Corynebacterium can inhibit the Agr quorum-sensing system of S. aureus, thus decrease the synthesis of virulence factors and attenuate skin inflammation. This review summarizes the mechanism of action of microbial quorum-sensing system in skin inflammation and various quorum-sensing inhibitors.

Dynamic regulation using a quorum-sensing circuit enhances the production of tyrosol by Escherichia coli / 生物工程学报

Tyrosol is a natural polyphenolic product that is widely used in chemical, pharmaceutical and food industries. Currently, the de novo synthesis of tyrosol by Escherichia coli suffers from issues such as low cell density and poor yield. Therefore, the phenylpyruvate decarboxylase mutant ARO10F138L/D218G obtained in our previous study was fused with an alcohol dehydrogenase from different microorganisms for fusion expression, and the optimal ARO10F138L/D218G-L-YahK produced 1.09 g/L tyrosol in shake flasks. In order to further improve tyrosol production, feaB, a key gene in the competing pathway of 4-hydroxyphenylacetic acid, was knocked out, and the resulted strain produced 1.26 g/L tyrosol with an increase of 21.15% compared to that of the control. To overcome the low cell density in tyrosol fermentation, the quorum-sensing circuit was used to dynamically regulate the tyrosol synthesis pathway, so as to alleviate the toxic effect of tyrosol on chassis cells and relieve the growth inhibition. Using this strategy, the yield of tyrosol was increased to 1.74 g/L, a 33.82% increase. In a 2 L fermenter, the production of tyrosol in the engineered strain TRFQ5 dynamically regulated by quorum-sensing reached 4.22 g/L with an OD600 of 42.88. Compared with those in the engineered strain TRF5 statically regulated by induced expression, the yield was increased by 38.58% and the OD600 was enhanced by 43.62%. The combination of blocking the competing pathway using gene knockout technology, and reducing the inhibitory effect of tyrosol toxicity on chassis cells through quorum-sensing dynamic regulation increased the production of tyrosol. This study may facilitate the biosynthesis of other chemicals with high toxicity.

In vitro antibacterial-antibiofilm effect of Hypericum atomarium Boiss and chemical composition

Abstract Treatment with plant is considered an effective option against increased antibiotic resistance. In this study antibiofilm activity of methanol (CH3OH), chloroform (CHCl3), ethyl acetate (EtOAc) and water (H2O) extracts of Hypericum atomarium Boiss. which is member of Hypericum genus was evaluated in Pseudomonas aeruginosa PAO1 and antibacterial performance against Gram (+) and Gram (-) strains and also bioactive compounds of extract were analysed using by HPLC and GC-MS. According to antibacterial activity test results the extracts were effective all Gram (+) bacteria and Gram (-) Chromobacterium violaceum (MICs ranging from 0.42 µg/ml to 4.3 mg). Inhibition effect of biofilm formation was found to be different rate in extracts (methanol-63%, chloroform-52%). The major flavonoids were detected (−)-epicatechin (2388.93 µg/ml) and (+)-catechin (788.94 µg/ml). The main phenolic acids were appeared as caffeic acid 277.34 µg/ml and chlorogenic acid 261.79 µg/ml. And according to GC results α-pinene was found main compound for three solvent extracts methanol, chloroform and ethyl acetate 67.05, 62.69, 49.28% rate respectively

Screening strategies for quorum sensing inhibitors in combating bacterial infections / 药物分析学报

Interference with quorum sensing(QS)represents an antivirulence strategy with a significant promise for the treatment of bacterial infections and a new approach to restoring antibiotic tolerance.Over the past two decades,a novel series of studies have reported that quorum quenching approaches and the discovery of quorum sensing inhibitors(QSIs)have a strong impact on the discovery of anti-infective drugs against various types of bacteria.The discovery of QSI was demonstrated to be an appropriate strategy to expand the anti-infective therapeutic approaches to complement classical antibiotics and antimicrobial agents.For the discovery of QSIs,diverse approaches exist and develop in-step with the scale of screening as well as specific QS systems.This review highlights the latest findings in strategies and methodologies for QSI screening,involving activity-based screening with bioassays,chemical methods to seek bacterial QS pathways for QSI discovery,virtual screening for QSI screening,and other potential tools for interpreting QS signaling,which are innovative routes for future efforts to discover additional QSIs to combat bacterial infections.

Using plant extracts and their active ingredients to inhibit bacterial biofilms / 生物工程学报

Numerous studies have reported that the resistance of biofilm bacteria to antibiotics can be up to 10-1 000 fold higher than that of planktonic bacteria. Bacterial biofilms are reported to be responsible for more than 80% of human microbial infection, posing great challenges to the healthcare sector. Many studies have reported that plant extracts and their active ingredients can inhibit the formation and development of bacterial biofilms, including reducing biofilm biomass and the number of viable bacteria in biofilms, as well as eradicating mature biofilms. This review summarized the plant extracts and their active ingredients that are inhibitory to bacterial biofilms, and analyzed the underpinning mechanisms. This review may serve as a reference for the development of plant drugs to prevent and treat biofilm infections.

Interações populacionais mediadas por quorum sensing na microbiota do soro-fermento utilizado na produção do queijo Canastra / Population interactions mediated by quorum sensing in the microbiota of the endogenous culture used in the production of canasta cheese

Bactérias regulam a expressão de diversos fenótipos de acordo com a sua densidade populacional, em um comportamento conhecido como quorum sensing. Em micro-organismos de origem alimentar, o quorum sensing pode influenciar na formação de biofilmes, produção de toxinas e de enzimas hidrolíticas. Em bactérias Gram-negativas a sinalização é normalmente mediada por moléculas de N-acilhomoserina lactona (AHLs), conhecidas por autoindutor 1 (AI-1). Estudos revelam a inibição do quorum sensing nestas bactérias por enzimas que degradam as AHLS, em um processo denominado quorum quenching. Tipicamente brasileiro, o queijo Canastra é um produto artesanal maturado, produzido a partir de leite cru e do pingo, um tipo de soro-fermento coletado e utilizado diariamente na produção. A composição microbiana do pingo é diversificada e característica da região produtora. Essa combinação de bactérias, única em cada queijaria, resulta em aroma e textura típicos. Enquanto a microbiota Gram-positiva contribui para o desenvolvimento de sabor, textura e aroma no produto, bactérias Gram-negativas nesses queijos são geralmente associadas à formação de olhaduras, aromas desagradáveis, má coagulação da massa e até à patogenicidade. Este trabalho visou analisar a interação entre a microbiota Gram-positiva e Gram-negativa presente no pingo pela detecção dos sistemas de quorum sensing e quorum quenching nas amostras. A presença de AHLs foi avaliada em 45 amostras de pingo, a partir da extração em acetato de etila acidificado e da avaliação dos extratos por meio de bioensaios com Agrobacterium tumefaciens WCF47(pCF218)(pCF372) e KYC55(pJZ410)(pJZ372)(pJZ384), resultando em apenas uma amostra positiva. Em seguida, 350 isolados foram obtidos a partir de 11 amostras de pingo, sendo 200 isolados classificados como Gram-positivos e 150 Gram-negativos. Os Gramnegativos foram avaliados quanto à produção de AHLs in vitro através de ensaio em placa utilizando as estirpes biossensoras A. tumefaciens WCF47(pCF218)(pCF372), Chromobacterium violaceum CV026 e Escherichia coli pSB403, resultando em 39 isolados produtores de AHLs, provenientes de 10 pingos diferentes. Já os isolados Gram-positivos foram analisados quanto à capacidade de inibição do QS utilizando as estirpes biossensoras C. violaceum CV026 e A. tumefaciens WCF47(pCF218)(pCF372), em meio suplementado com C6-HSL ou 3-oxo-C12-HSL. Foi detectada a inibição total da resposta ao quórum por 78 isolados testados, enquanto a inibição parcial foi provocada por outros 63. A inibição do crescimento das estirpes biossensoras também foi observada para 24 isolados. Os isolados promotores de inibição parcial foram recultivados em meio mínimo com C6-HSL ou 3-oxo-C12-HSL como únicas fontes de carbono. Foram recuperados 28 isolados, e a ação desses sobre diferentes substratos foi avaliada, resultando em 22 isolados produtores de lactonases e 6 produtores de acilase. Os 39 isolados Gram-negativos e os 28 isolados Gram-positivos finais foram identificados por MALDI-TOF MS, resultando, segundo o conhecimento do autor, no primeiro relato de produção de AHLs por Pseudomonas fulva, Enterobacter xiangfangensis e Lelliottia amnigena, bem como a produção de lactonases por Staphylococcus xylosus e a produção de acilase por S. aureus, Microbacterium maritypicum e Rothia kristinae. Este trabalho mostrou que interações populacionais mediadas por quorum sensing dependente de AHLs na microbiota do soro-fermento são possíveis. Porém, essas interações estão propensas a serem inibidas por meio de lactonases e acilases produzidas por parte das bactérias Gram-positivas

Bacteria regulate the expression of different phenotypes according to their population density, in a behavior known as quorum sensing. In food-borne microorganisms, quorum sensing can influence the formation of biofilms, production of toxins and hydrolytic enzymes. In Gram-negative bacteria, signaling is normally mediated by Nacyl homoserine lactone molecules (AHLs), known as autoinducer 1 (AI-1). Studies reveal the inhibition of quorum sensing in these bacteria by enzymes that degrade AHLS, in a process called quorum quenching. Typically Brazilian, Canastra cheese is a matured artisanal product, produced from raw milk and pingo, a type of endogenous culture collected and used daily in production. The microbial composition of pingo is diverse and characteristic of the producing region. This combination of bacteria, unique in each cheese factory, results in a typical aroma and texture. While the Gram-positive microbiota contributes to the development of flavor, texture and aroma in the product, Gram-negative bacteria in these cheeses are generally associated with the formation of eyes, off-flavors, poor curd coagulation and even pathogenicity. Thus, this work aimed to analyze the interaction between the Gram-positive and Gram-negative microbiota present in this culture by detecting quorum sensing and quorum quenching systems in the samples. The presence of AHLs was evaluated in 45 samples of pingo, with extraction with acidified ethyl acetate and the evaluation of the extracts through bioassays with Agrobacterium tumefaciens WCF47(pCF218)(pCF372) and KYC55(pJZ410)(pJZ372)(pJZ384 ), resulting in only one positive sample. Then, 350 isolates were obtained from 11 endogenous culture samples, with 200 being classified as Gram-positive and 150 Gram-negative. Gram-negatives were evaluated for the production of AHLs in vitro by plaque assay using the biosensor strains A. tumefaciens WCF47(pCF218)(pCF372), Chromobacterium violaceum CV026 and Escherichia coli pSB403, resulting in 39 AHL-producing isolates from 10 different samples. Gram-positive isolates were analyzed for their ability to inhibit quorum sensing using biosensor strains C. violaceum CV026 and A. tumefaciens WCF47(pCF218)(pCF372), in medium supplemented with N-hexanoyl-L-homoserine lactone or 3-oxo-dodecanoyl-Lhomoserine lactone. Total inhibition of the quorum response was detected by 78 tested isolates, while partial inhibition was caused by 63. Growth inhibition of biosensor strains was also observed for 24 isolates. Partial inhibition promoter isolates were recultured on minimal medium with C6-HSL or 3-oxo-C12-HSL as sole carbon sources. Twenty-eight isolates were recovered, and the action of these isolates on different substrates was evaluated, resulting in 22 lactonase producers and 6 acylase producers. The 39 Gram-negative isolates and the final 28 Grampositive isolates were identified by MALDI-TOF MS, resulting, to the best of the author's knowledge, in the first report of AHL production by Pseudomonas fulva, Enterobacter xiangfangensis and Lelliottia amnigena, as well as the lactonase production by Staphylococcus xylosus and acylase production by S. aureus, Microbacterium maritypicum and Rothia kristinae. This work demonstrated that population interactions mediated by AHLs-dependent quorum sensing in Canastra cheese endogenous culture microbiota are possible. However, these interactions are prone to inhibition by lactonases and acylases produced by Gram-positive bacteria

Corchorus olitorius aqueous extract attenuates quorum sensing-regulated virulence factor production and biofilm formation

Objective:To investigate the effect of Corchorus olitorius aqueous fraction (COAF) on quorum sensing (QS)-regulated virulence factors and biofilm formation in Pseudomonas aeruginosa (PAO1). Methods:The preliminary screening of the anti-QS effect of COAF was performed by evaluating the anti-pathogenic activity against Chromobacterium violaceum CV026 biosensor strain. Next, the inhibitory effects of COAF on QS-regulated pyocyanin production, proteolytic and elastolytic activities, swarming motility, and biofilm formation were evaluated in PAO1.Results:The results showed that the treatment of COAF significantly decreased the biofilm biomass, attenuated virulence factors, and inhibited swarming motility of PAO1 without affecting the growth of the bacteria in a dose-dependent manner. COAF at 2000 μg/mL significantly decreased Las B elastase activity in PAO1 culture, exopolysaccharide production, swarming motility, pyocyanin level, and biomass of PAO1 by 55％ (P<0.05), 60％ (P<0.01), 61％ (P<0.01), 65％(P<0.01) and 73％ (P<0.01), respectively. In addition, the production of violacein was decreased by 62％ (P<0.01) with the treatment of a high dose of COAF. Conclusions:These findings indicate that COAF can be a potential source of anti-QS agents.

The effect of tryptamine on Serratia marcescens, Pseudomonas aeruginosa and Escherichia coli

Aims@#Tryptamine is an amine compound derived from tryptophan by decarboxylation process. This compound can be found in fermented food and beverages, and in human gut and skin as well. This study aims to investigate the effect of tryptamine, on Gram-negative bacteria, namely Escherichia coli, Serratia marcescens and Pseudomonas aeruginosa.@*Methodology and results@#In this study, we used E. coli, S. marcescens and P. aeruginosa due to their relatively observable quorum sensing-regulated phenotype, such as motility, prodigiosin and pyocyanin sequentially. Our results showed that tryptamine started to inhibit the growth and prodigiosin production of S. marcescens at concentration 250 μg/mL, while it inhibits the growth and pyocyanin production of P. aeruginosa at concentration 250 μg/mL and 500 μg/mL, respectively. Tryptamine inhibits both the growth and motility of E. coli at concentration 100 μg/mL. @*Conclusion, significance and impact of study@# These results suggest that tryptamine is able to inhibit the growth of E. coli, S. marcescens and P. aeruginosa at relatively high concentration, thus decreases the quorum sensing-regulated phenotypes. It implies that the growth and quorum sensing of Gram-negative bacteria most likely will not be affected by the low concentration of tryptamine that present in the gut.

Potential of polyphenols in curbing quorum sensing and biofilm formation in Gram-negative pathogens

Polyphenols are the secondary metabolic products of plants and are considered as active constituents to possess therapeutic effects. To date, a vast number of scientific literature addressed the potential of polyphenols as bio-efficient compounds owing to their structural diversity. Due to the presence of several hydroxyl groups, they are metabolized quickly due to conjugation reaction and thus, readily produce toxic metabolites as a defense material against many pathogens, reflecting their safety strategy. This review focuses on the anti-quorum sensing and biofilm inhibition activity of polyphenols, which display their potential to treat bacterial infections by combating the virulence caused by pathogenic agents. Thus, for mitigating quorum sensing-controlled pathogenesis, the use of polyphenol-based phytochemicals holds immense potential to cure infections. The application of polyphenol as sensitizing agent/ adjuvant therapeutics which act in synergism with antibiotics is highly remarkable.

Transcriptional regulation of pilABCD by OpaR in Vibrio parahaemolyticus / 中华微生物学和免疫学杂志

Objective:To study the transcriptional regulation of pilABCD by the master quorum sensing (QS) regulator OpaR in Vibrio parahaemolyticus. Methods:Total RNAs were extracted from the wild type (WT) and opaR mutant (Δ opaR) strain. Quantitative real-time PCR (qPCR) was employed to calculate the transcriptional variation of pilA (the first gene of pilABCD operon) between WT and Δ opaR. The regulatory DNA region of pilABCD was cloned into the corresponding restriction endonuclease sites of pHRP309 harboring a promoterless lacZ reporter gene. The recombinant pHRP309 plasmid was then transferred into WT and Δ opaR, respectively, to detect the β-galactosidase activity in cellular extracts using a β-Galactosidase Enzyme Assay System (Promega). The primer extension assay was applied to map the transcription start site of pilABCD using the total RNAs extracted from the WT strain as the template. The regulatory DNA region of pilABCD was amplified by PCR, and the over-expressed His-OpaR was purified under native conditions with nickel loaded HiTrap Chelating Sepharose columns (Amersham). Thereafter, the electrophoretic mobility shift assay (EMSA) was applied to analyze the DNA-binding activity of His-OpaR to the target DNA in vitro, and the DNase I footprinting assay was further employed to detect the DNA-binding sites of His-OpaR within the target DNA. Results:The results of qPCR and LacZ fusion assays showed that OpaR activated the transcription of pilABCD, leading to a gradual increase in the expression level of pilA with the extension of culture time. The primer extension assay detected only one transcription start site located at 155 bp upstream of pilA. The results of EMSA and DNase Ⅰ footprinting assays showed that His-OpaR protected two DNA regions located from -246 to -197 bp and -181 to -131 bp upstream of pilA. Conclusions:Vibrio parahaemolyticus OpaR activated the transcription of pilABCD in a direct manner.

Anti-infective potential of a quorum modulatory polyherbal extract (panchvalkal) against certain pathogenic bacteria

BackgroundIn view of the gravity of the problem of antimicrobial resistance among pathogenic bacteria against conventional bactericidal agents, investigation on alternative approaches to combat bacterial infections is warranted.ObjectiveCurrent study aimed at investigating anti-infective potential of a polyherbal ayurvedic formulation namely panchvalkal against three different pathogenic bacteria.Materials and methodsThe panchvalkal formulation available as Pentaphyte P5® was tested for its possible in vitro quorum-modulatory potential against Chromobacterium violaceum, Serratia marcescens, and Staphylococcus aureus through broth dilution assay. Invivo efficacy was demonstrated employing Caenorhabditis elegans as the model host for test pathogens.ResultsThis formulation was found to exert quorum-modulatory effect on C. violaceum, S. marcescens, and S. aureus at 250–750 μg/ml. Besides altering production of the quorum sensing-regulated pigments in these bacteria, the test formulation also had in vitro effect on antibiotic susceptibility, catalase activity and haemolytic potential of the pathogens. Invivo assay confirmed the protective effect of this panchvalkal formulation on C. elegans, when challenged with the pathogenic bacteria. Repeated exposure of S. aureus to panchvalkal did not induce resistance in this bacterium.ConclusionTo the best of our awareness, this the first report on quorum-modulatory potential of panchvalkal formulation, validating the anti-infective potential and moderate prebiotic property of this polyherbal preparation.

antibacterial, antioxidant activities, and phytoconstituents analysis of medicinal plants used in Benin: Acacia macrostachya (Rchb

Microbial infections remain public health problems because of the upsurge of bacterial resistance. The presentstudy aimed to evaluate the anti-quorum sensing, antimicrobial activities, and chemical compositions ofAcacia macrostachya. Total phenolic, flavonoid, and condensed tannin content were determined according toFolin–Ciocalteu, aluminum chloride, and Broadhurst methods, respectively. The microdilution method usingp-iodonitrothétrazolium was used to evaluate the antibacterial activity. Inhibition of pyocyanin and violaceinproduction by extract and fraction was used to evaluate anti-quorum sensing activity. The antioxidant activitywas evaluated using 2,2-diphenyl-1-picryl-hydrazyl, Ferric reducing, and hydrogen peroxide scavengingmethods. The minimum inhibitory concentration of the extracts and fractions ranged from 0.312 to 5 mg/ml.At 100 µg/ml, ethyl acetate fraction significantly inhibited the production of violacein (56.45%) and pyocyanin(48.88%). The total phenolic, flavonoids, and condensed tannin contents ranged from 31.85 ± 0.31 to 21.26± 0.67 mg gallic acid equivalent (GAE)/100 mg, 26.35 ± 0.71 to 25.42 ± 0.36 mg quercetin equivalent (QE)/100mg, and 18.24 ± 0.12 to 15.9 ± 0.17 mg Catechin equivalent (CE)/100 mg, respectively. The antioxidantactivity correlates with phenolic, flavonoids, and tannin contents. High Pressure Liquide Chromatography(HPLC) analysis of the ethyl acetate fraction allowed to identify three phenolic acids and five flavonoids. Theresults described here could justify the use of A. macrostachya by traditional healers to treat infections, andparticularly, gastrointestinal disorders.

Effects of biotic and abiotic factors on biofilm growth dynamics and their heterogeneous response to antibiotic challenge

With the emergence of multidrug-resistant ‘superbug’, conventional treatments become obsolete. Quorumquenching (QQ), enzyme-dependent alteration of quorum sensing (QS), is now considered as a promisingantimicrobial therapy because of its potentiality to impede virulence gene expression without resulting ingrowth inhibition and antibiotic resistance. In our study, we intended to compare between two major QQenzyme groups (i.e., AHL lactonases and AHL acylases) in terms of their structural and functional aspects.The amino acid composition-based principal component analysis (PCA) suggested that probably there is nostructural and functional overlapping between the two groups of enzymes as well as within the lactonaseenzymes but the acylases may functionally be affected by one another. In subcellular localization analysis,we also found that most lactonases are cytoplasmic while acylases are periplasmic. Investigation on thesecondary structural features showed random coil dominates over a-helix and b-sheet in all evaluatedenzymes. For structural comparison, the tertiary structures of the selected proteins were modelled andsubmitted to the PMDB database (Accession ID: PM0081007 to PM0081018). Interestingly, sequencealignment revealed the presence of several conserved domains important for functions in both proteingroups. In addition, three amino acid residues, namely aspartic acid, histidine, and isoleucine, were commonin the active sites of all protein models while most frequent ligands were found to be 3C7, FEO, and PAC.Importantly, binding interactions of predicted ligands were similar to that of native QS signal molecules.Furthermore, hydrogen bonds analysis suggested six proteins are more stable than others. We believe thatthe knowledge of this comparative study could be useful for further research in the development of QSbased universal antibacterial strategies

Computational prediction of active sites and ligands in different AHL quorum quenching lactonases and acylases

Rice tungro is a serious viral disease of rice resulting from infection by two viruses, Rice tungro bacilliformvirus and Rice tungro spherical virus. To gain molecular insights into the global gene expression changes inrice during tungro, a comparative whole genome transcriptome study was performed on healthy and tungroaffected rice plants using Illumina Hiseq 2500. About 10 GB of sequenced data comprising about 50 millionpaired end reads per sample were then aligned on to the rice genome. Gene expression analysis revealedaround 959 transcripts, related to various cellular pathways concerning stress response and hormonal homeostasis to be differentially expressed. The data was validated through qRT-PCR. Gene ontology and pathwayanalyses revealed enrichment of transcripts and processes similar to the differentially expressed genes categories. In short, the present study is a comprehensive coverage of the differential gene expression landscapeand provides molecular insights into the infection dynamics of the rice-tungro virus system

Influence of abaR gene knockout on growth metabolism and biofilm formation of Acinetobacter baumannii / 中华烧伤杂志

Objective@#To investigate the influence of abaR gene knockout on growth metabolism and biofilm formation of Acinetobacter baumannii.@*Methods@#The abaR gene was knocked out from Acinetobacter baumannii standard strain ATCC 17978 (wild strain) by homologous recombination method, and then the ATCC 17978 abaR knockout strain (ATCC 17978/ΔabaR: : Kn) was obtained and verified by polymerase chain reaction (PCR) electrophoresis and sequencing. The growth curves of Acinetobacter baumannii wild strain and Acinetobacter baumannii knockout strain were determined by microplate reader within cultivation hour (CH) 18, and the biofilm formation ability was measured by crystal violet staining at CH 8, 24, and 48, respectively. The sample number at each time point was 3.The results were denoted as absorbance value. Data were processed with analysis of variance of factorial design, one-way analysis of variance, t test, and least-significant difference test.@*Results@#(1) The length of PCR product of target fragment ΔabaR: : Kn was 3 029 bp. The abaR gene was knocked out to obtain the knockout strain ATCC 17978/ΔabaR: : Kn. The length of PCR product of the knockout strain was 3 300 bp. The abaR gene was successfully knocked out. (2) At CH 2, 3, and 4, the absorbance values of Acinetobacter baumannii wild strain were slightly higher than those of the knockout strain. The absorbance values of Acinetobacter baumannii wild strain and knockout strain were similar from CH 5 to 18. (3) At CH 8 and 24, the biofilm formation ability of Acinetobacter baumannii wild strains (0.644±0.066, 0.574±0.184) was similar to that of knockout strains (0.559±0.008, 0.394±0.030, t=2.209, 1.167, P>0.05). At CH 48, the biofilm formation ability of Acinetobacter baumannii wild strains (1.157±0.259) was significantly stronger than that of Acinetobacter baumannii knockout strains (0.576±0.026, t=3.865, P<0.05). The biofilm formation ability of Acinetobacter baumannii wild strains at CH 48 was significantly stronger than that at CH 8 and 24 (P<0.05). The biofilm formation ability of Acinetobacter baumannii knockout strains at CH 24 was significantly weaker than that at CH 8 and 48 (P<0.05).@*Conclusions@#The abaR gene of Acinetobacter baumannii ATCC 17978 can be successfully knocked out by homologous recombination to obtain its knockout strain ATCC 17978/ΔabaR: : Kn. The abaR gene does not affect the growth and metabolism of Acinetobacter baumanniibut can weaken its biofilm formation ability.

Screening Quorum-sensing-associated sRNA and construction of its overexpression and deletion mutant in Pseudomonas aeruginosa / 医学研究生学报

ObjectiveQuorum-sensing (QS) and small regulatory RNA (sRNA) play key regulatory roles in many signaling cascades of Pseudomonas aeruginosa. To investigate whether sRNA is involved in P. aeruginosa QS system, screening QS system-related sRNA, and to construct sRNA overexpression and deletion strains of Pseudomonas aeruginosa for further study of sRNA function.MethodsSRNA associated with the QS system was screened by qPCR and RNA-sequencing (RNA-seq). The target gene were amplified by PCR and inserted into the overexpression vector pROp200 or the homologous recombination vector pGSM-MR, respectively. The connection reaction solution of pROp200-sRNA and pGSM-ΔsRNA was transformed into Escherichia coli DH5a and SM10lp, respectively. The recombinant vectors were identified by PCR. The pROp200-sRNA was transformed into PAO1 by heat shock method, and the pGSM-ΔsRNA was transferred from SM10lp to PAO1 by conjugation. SRNA overexpression and deletion strains were identified by PCR, DNA sequencing and qPCR, the determination of the growth curves and the pyocyanin levels of strains.ResultsFive QS -associated sRNA P26, P5316.1, P30, P34 and AmiL were successfully screened by RNA-seq and qPCR. PCR, DNA sequencing and qPCR showed that sRNA of AmiL, P30 and P34 overexpression and knockout were successful. Compared with wild-type strain, sRNA overexpression and knockout had no significant effect on bacterial growth curve. It were notably that overexpression of AmiL and P30 inhibited and increase the production of pyocyanin, respectively (P0.05).ConclusionThe sRNA overexpression and deletion strains have been successfully constructed and can be used to study the regulatory relationship between sRNA and QS systems, and to further functional study.