Chromobacterium Violaceum Research Articles

The Regulatory Protein ChuP Connects Heme and Siderophore-Mediated Iron Acquisition Systems Required for Chromobacterium violaceum Virulence.

Chromobacterium violaceum is an environmental Gram-negative beta-proteobacterium that causes systemic infections in humans. C. violaceum uses siderophore-based iron acquisition systems to overcome the host-imposed iron limitation, but its capacity to use other iron sources is unknown. In this work, we characterized ChuPRSTUV as a heme utilization system employed by C. violaceum to explore an important iron reservoir in mammalian hosts, free heme and hemoproteins. We demonstrate that the chuPRSTUV genes comprise a Fur-repressed operon that is expressed under iron limitation. The chu operon potentially encodes a small regulatory protein (ChuP), an outer membrane TonB-dependent receptor (ChuR), a heme degradation enzyme (ChuS), and an inner membrane ABC transporter (ChuTUV). Our nutrition growth experiments using C. violaceum chu deletion mutants revealed that, with the exception of chuS, all genes of the chu operon are required for heme and hemoglobin utilization in C. violaceum. The mutant strains without chuP displayed increased siderophore halos on CAS plate assays. Significantly, we demonstrate that ChuP connects heme and siderophore utilization by acting as a positive regulator of chuR and vbuA, which encode the TonB-dependent receptors for the uptake of heme (ChuR) and the siderophore viobactin (VbuA). Our data favor a model of ChuP as a heme-binding post-transcriptional regulator. Moreover, our virulence data in a mice model of acute infection demonstrate that C. violaceum uses both heme and siderophore for iron acquisition during infection, with a preference for siderophores over the Chu heme utilization system.

Accurate Identification of Diverse N-acyl Homoserine Lactones in Marine Vibrio fluvialis by UHPLC-MS/MS.

Vibrio fluvialis is a marine opportunistic pathogen that frequently causes diseases in aquatic animals and humans. V. fluvialis can produce quorum sensing signaling molecules to coordinate cell density-dependent behavioral changes, including N-acyl homoserine lactone (AHL), which acts as a vital mediator of virulence-associated gene expression. Currently, several AHL molecules in V. fluvialis have been detected via biological and physicochemical methods, although different detection approaches have generated diverse AHL profiles. Here, we describe the AHL-producing bacterium, V. fluvialis BJ-1, which was isolated from marine sediments from the East China Sea. V. fluvialis BJ-1 could stimulate AHL-mediated β-galactosidase synthesis of the biosensor Agrobacterium tumefaciens NTL4 (pZLR4) but couldnot induce violacein production in the AHL reporter strain, Chromobacterium violaceum CV026. This bacterial isolate exhibited strong AHL-producing activity atlowcelldensity; however, the AHL activity declined when populationdensity remained at high levels. Analysis of the AHLs by Ultra-High-Performance Liquid Chromatography tandem Mass Spectrometry demonstrated that V. fluvialis BJ-1 produced five different AHL signaling molecules, including two linear chain AHL products (C8- and C10-HSL), and three β-carbon-oxidative AHL products (3-O-C8-, 3-O-C10- and 3-O-C12-HSL). Significantly, the present study is the first to accurately define the AHL profile of marine V. fluvialis. In future, the coupling of UHPLC to ESI-MS/MS is expected to be utilized for the accurate determination of AHL profiles in marine Vibrio.

Aromatherapeutic essential oils and their pharmaceutical combinations: Tools for inhibition of quorum sensing activity and biofilm formation of human pathogens

Background and Aims: Aromatherapy, as one of the complementary therapies, uses essential oils as the main therapeutic agents to treat several diseases. In the present study, it was aimed to investigate inhibition of quorum sensing (QS) and biofilm formation of aromatherapeutic essential oils (AEOs) and their pharmaceutical combinations (PC-I and PC-II). Methods: The anti-QS potential of AEOs were determined using the biosensor strains Chromobacterium violaceum ATCC 12472 and Pseudomonas aeruginosa PAO1. Anti-QS activity was detected by agar-well diffusion and violacein pigment inhibition assays. Blocking of PAO1 swim and swarm motilities and biofilm formation was also performed. Results: Most of the AEOs demonstrated highly active (>95%) violacein pigment inhibition. Additionally, they inhibited swarming (40.34%-72.80%) and swimming (20.06%-50.08%) motilities of PAO1. Moreover, the majority of AEOs also decreased the biofilm formation, particularly on P. aeruginosa and S. aureus. Conclusion: Consequently, aromatherapeutic formulations might be a complementary or prophylactic cure for infectious disease by their anti-QS and antibiofilm activities rather than just antimicrobial effects.

Improvement in Violacein Production by Utilizing Formic Acid to Induce Quorum Sensing in Chromobacterium violaceum.

Violacein has attracted increasing attention due to its various biological activities, such as antibacterial, antifungal, antioxidative, and antitumor effects. To improve violacein production, formic acid (FA) was added to a culture medium, which resulted in a 20% increase (1.02 g/L) compared to the no-FA-addition group (0.85 g/L). The use of a stirred-tank bioreactor system also improved violacein production (by 0.56 g/L). A quorum-sensing (QS)-related gene (cviI) was induced by FA treatment, which revealed that the mechanism induced by FA utilized regulation of the cviI gene to induce the vio gene cluster for violacein production. To analyze the antioxidative properties of the violacein produced, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) scavenging tests were conducted, and results reveal that the values of the 50% inhibitory concentration (IC50) of DPPH and ABTS were 0.286 and 0.182 g/L, respectively. Violacein also showed strong inhibitory activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis). In summary, this study found that the addition of formic acid can promote QS of Chromobacterium violaceum, thereby promoting the synthesis of violacein. Subsequently, the promoting effect was also evaluated in a bioreactor system. These findings will be helpful in establishing an economically beneficial production model for violacein in future work.

Effect of (+) usnic Acid on Pigment Production in Bacteria

Antibiotic resistance is a universal problem in bacterial infections. Hence it gives high priority for new therapeutic methods to alternate conventional antibiotic treatment. Pigment production is one of the virulence characteristics of bacteria regulated by a quorum-sensing mechanism. Antiquorum sensing activities will not directly affect the viability of bacteria; however, they will reduce the pathogenicity of bacteria. Thereby it gives an adverse probability of the development of drug resistance. Aim of our study is to evaluate the activity of (+) usnic acid on pigment production in Pseudomonas aeruginosa MTCC 2453, Chromobacterium violaceum MTCC 2656 and Serratia marcescens MTCC 8708. (+) usnic acid eluted by column chromatography. Dimethyl sulphoxide (DMSO) was used as the solvent for (+) usnic acid. Antibacterial activity determined by Agar well diffusion and broth microdilution methods. Effect on pigment production was assessed by spectroscopy. (+) usnic acid showed accumulative inhibition as its concentration increases on pigment production by Pseudomonas aeruginosa MTCC 2453, Chromobacterium violaceum MTCC 2656 and Serratia marcescens MTCC 8708. The lowest concentrations of (+) usnic acid manifested 50% inhibition of pigment production was 122.67, 87.73 and 205.26 µg/ml respectively on above mentioned order in bacteria. The concentration of (+) usnic acid that showed pigment production inhibition did not hinder the growth of the bacteria, but it can reduce the virulence of the bacteria. This property can be used to resolve the drug resistance in bacteria. Further studies are required to check the action of (+) usnic acid on other virulence factors of the bacteria to prove the quorum quenching activity.

New diarylpentanoids and chalcones as potential antimicrobial adjuvants

Antimicrobial resistance arises due to several adaptation mechanisms, being the overexpression of efflux pumps (EPs) one of the most worrisome. In bacteria, EPs can also play important roles in virulence, quorum-sensing (QS) and biofilm formation. To identify new potential antimicrobial adjuvants, a library of diarylpentanoids and chalcones was synthesized and tested. These compounds presented encouraging results in potentiating the activity of antimicrobials, being diarylpentanoid 13 the most promising. Compounds 9, 13, 16, 19, 22, and 23 displayed EP inhibitory effect, mainly in Staphylococcus aureus 272123. Compounds 13, 19, 22, and 23 exhibited inhibitory effect on biofilm formation in S. aureus 272,123 while 13 and 22 inhibited QS in the pair Sphingomonas paucimobilis Ezf 10–17 and Chromobacterium violaceum CV026. The overall results, demonstrated that diarylpentanoid 13 and chalcone 22 were active against all the resistance mechanisms tested, suggesting their potential as antimicrobial adjuvants.

Computational screening of natural compounds as putative quorum sensing inhibitors targeting drug resistance bacteria: Molecular docking and molecular dynamics simulations

Quorum sensing (QS) is a bacterial communication strategy controlling cells density, biofilm formation, virulence, sporulation, and survival. Since QS is considered a virulence factor in drug-resistant pathogenic bacteria, inhibition of QS can contribute to control the spread of these bacteria. We propose in this study to test in silico, 19 natural compounds for their potential to inhibit QS transcriptional regulators of Pseudomonas aeruginosa (LasR and PqsE) and Chromobacterium violaceum (CviR and CviR′). Molecular docking was performed to explore the binding energies between selected compounds, and QS signaling proteins. Additionally, molecular dynamics (MD) simulations of the complexes protein-ligand were tested to evaluate the stability of the complexs throughout the simulation process. The simulation interaction diagram (SID) was achieved to compute the radius of gyration (rGyr), solvent accessible surface area (SASA), intramolecular HBs, molecular surface area (MolSA), and polar surface area (PSA). Additionally, the physicochemical properties, pharmacokinetics, drug-likeness, and toxicity analysis of the best-selected compounds were determined. Among these compounds, catechin and nakinadine B were identified as potent QS antagonists that showed the best XP GScore and stable interaction during molecular dynamic simulation. Catechin interacts with LasR and CviR′ displaying XP GScore −10.969 kcal/mol and −9.936 kcal/mol respectively. Additionally, nakinadine B interacts with PqsE and CviR giving XP GScore −7.442 kcal/mol and −10.34 kcal/mol respectively. RMSD plot analysis showed that both catechin and nakinadine B were stable during 50 ns simulation time with the tested target proteins. The predictive result of toxicity demonstrated that catechin and nakinadine B doesn't induce cytotoxicity, immunotoxicity, carcinogenicity, mutagenicity, hepatotoxicity and were at medium risk for hERG inhibition. Also they were found to be inactive for androgen receptor and aromatase. These results imply that catechin and nakinadine B may be suggested as QS modulators, which may reduce the virulence factors of drug-resistant bacteria.

Indole inhibits quorum sensing‐dependent phenotypes and virulence of acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus

Acute hepatopancreatic necrosis syndrome (AHPND) caused by a unique Vibrio parahaemolyticus strain (VPAHPND) has emerged as a serious disease of cultured shrimps and is causing great economic losses worldwide. In this work, the effects of indole on quorum sensing-dependent (QS) phenotypes of VPAHPND were assessed. In QS-inhibitory bioassay using biomonitor strains, indole could interfere with N-acyl homoserine lactones (AHL)-mediated violacein pigment production of Chromobacterium violaceum, and autoinducer-1 (AI-1) and autoinducer-2 (AI-2)-mediated QS response (bioluminescence) in V. campbellii. Further testing of indole with VPAHPND demonstrated significant decrease in the swimming and swarming motilities. In addition, VPAHPND grown in the presence of indole exhibited a reduction in biofilm formation, extracellular polymeric substances (EPSs) production and autoaggregation index. However, indole did not affect the ability of VPAHPND to use ferrous sulphate (FeSO4) as an iron source. Interestingly, indole reduced the expression of pirA (~2 fold), pirB (~2 fold), cpsA (~1.5 fold) and scrA (~1.7 fold) resulting in the reduction of toxin and capsule production. Lastly, indole-treated VPAHPND exhibited lower virulence towards an infected model and its specific host, Galleria mellonella larvae and Litopenaeus vannamei respectively. These demonstrated the effects of indole in reducing multiple QS-dependent phenotypes and virulence of VPAHPND. Thus, using indole, indole-containing compounds, or indole-producing organisms might be an attractive anti-virulence strategy to control infections caused by VPAHPND.

Identification of a 3-(5-methyl-2-thiazolylamino)phthalide as a new minor groove agent

A new 3-(5-methyl-2-thiazolylamino)phthalide molecule, 3-((5-methylthiazol-2-yl)amino)isobenzofuran-1(3H)-one, was synthesized and characterized experimentally by FT-IR, NMR, UV-Vis, and single-crystal X-ray analysis and theoretically by quantum chemical calculations. The single-crystal X-ray studies revealed that the compound crystallizes in the monoclinic space group P-21/c with unit-cell parameters a = 8.0550(6) Å, b = 6.1386(3) Å, c = 23.3228(18) Å, β = 97.724(6)° and Z = 4. Optimized geometries and the vibrational frequencies were studied at the density functional theory (DFT) level by using the hybrid functional B3LYP with a 6-311 G (d,p) basis set. The title compound was evaluated for its anti-quorum sensing (anti-QS) activity on Chromobacterium violaceum 12472 and additionally for its antibacterial activity against Staphylococcus aureus 29213, Staphylococcus epidermidis 12228, Pseudomonas aeruginosa 27853, Escherichia coli 25922, and Proteus mirabilis 14153. The lowest MIC value was 0.24 μg/mL for S. aureus 29213 and the highest MIC value was 30.75 μg/mL for E. coli 25922. While anti-bacterial activity was observed in those other than the S. epidermidis and P. Mirabilis, anti-QS activity wasn’t detected. Investigations on dsDNA binding affinity indicate that the title compound binds to dsDNA via the groove binding mode. Molecular docking calculations and molecular dynamics simulations results showed also that the title compound prefers binding to the minor groove of dsDNA and remains stable in the minor groove throughout the molecular dynamics simulation. Communicated by Ramaswamy H. Sarma

EFFECT OF ISOFLAVONES AS ANTIBACTERIAL AND ANTI-QUORUM SENSING AGENTS AGAINST CHROMOBACTERIUM VIOLACEUM

Multidrug resistance is one of the emerging challenges confronted by the human race by pathogenic microorganisms causing dreadful diseases. Usage of antibiotics inappropriately has caused resistance which could lead to extreme consequences on the lives of humans. Quorum sensing (QS) is communication between cells based on the bacterial population and density. QS plays a vital role in bacterial virulence and emerging bacterial resistance. Chromobacterium violaceum aids in detecting QS modulation which is measured by violacein pigment quantification. Genistein and daidzein are isoflavones-phytoestrogen found to be beneficial in managing post menopause systems and also antioxidant-rich. The present study was conducted to understand whether these phytoestrogens genistein and daidzein interfere to inhibit biofilm formation and quorum sensing by preventing cross talk between bacteria. AntimicrobialChromobacterium violaceum. Results indicated the cytotoxic effect of genistein wherein daidzein and genistein were found to have anti-quorum sensing and biofilm inhibition. This could be of therapeutic influence against antibiotic resistance in future.

Inhibition of Quorum Sensing Regulated Virulence Factors and Biofilm Formation by Eucalyptus globulus against Multidrug-Resistant Pseudomonas aeruginosa.

ObjectivesThe quorum-sensing–inhibitory and anti-biofilm activities of the methanol extract of E. globulus leaves were determined against clinically isolated multidrug-resistant Pseudomonas aeruginosa.MethodsThe preliminary anti-quorum–sensing (AQS) activity of eucalyptus was investigated against a biosensor strain Chromobacterium violaceum ATCC 12472 (CV12472) by using the agar well diffusion method. The effect of sub-minimum inhibitory concentrations (sub-MICs) of the methanol extract of eucalyptus on different quorum-sensing–regulated virulence factors, such as swarming motility, pyocyanin pigment, exopolysaccharide (EPS), and biofilm formation, against clinical isolates (CIs 2, 3, and 4) and reference PA01 of Pseudomonas aeruginosa were determined using the swarm diameter (mm)-measurement method, chloroform extraction method, phenol (5%)-sulphuric acid (concentrated) method, and the microtiter plate assay respectively, and the inhibition (%) in formation were calculated.ResultsThe preliminary AQS activity (violacein pigment inhibition) of eucalyptus was confirmed against Chromobacterium violaceum ATCC 12472 (CV12472). The eucalyptus extract also showed concentration-dependent inhibition (%) of swarming motility, pyocyanin pigment, EPS, and biofilm formation in different CIs and PA01 of P. aeruginosa.ConclusionOur results revealed the effectiveness of the E. globulus extract for the regulation of quorum-sensing–dependent virulence factors and biofilm formation at a reduced dose (sub-MICs) and suggest that E. globulus may be a therapeutic agent for curing and controlling bacterial infection and thereby reducing the possibility of resistance development in pathogenic strains.

Terazosin Interferes with Quorum Sensing and Type Three Secretion System and Diminishes the Bacterial Espionage to Mitigate the Salmonella Typhimurium Pathogenesis.

Salmonella enterica is an invasive intracellular pathogen and hires diverse systems to manipulate its survival in the host cells. Salmonella could eavesdrop on the host cells, sensing and responding to the produced adrenergic hormones and other neurotransmitters, which results in the augmentation of its virulence and establishes its accommodation in host cells. The current study aims to assess the anti-virulence effect of α-adrenergic antagonist terazosin on S. Typhimurium. Our findings show that terazosin significantly reduced S. Typhimurium adhesion and biofilm formation. Furthermore, terazosin significantly decreased invasion and intracellular replication of S. Typhimurium. Interestingly, in vivo, terazosin protected the mice from S. Typhimurium pathogenesis. To understand the terazosin anti-virulence activity, its effect on quorum sensing (QS), bacterial espionage, and type three secretion system (T3SS) was studied. Strikingly, terazosin competed on the membranal sensors that sense adrenergic hormones and down-regulated their encoding genes, which indicates the ability of terazosin to diminish the bacterial eavesdropping on the host cells. Moreover, terazosin significantly reduced the Chromobacterium violaceum QS-controlled pigment production and interfered with the QS receptor Lux-homolog Salmonella SdiA, which indicates the possible terazosin-mediated anti-QS activity. Furthermore, terazosin down-regulated the expression of T3SS encoding genes. In conclusion, terazosin may mitigate S. Typhimurium virulence owing to its hindering QS and down-regulating T3SS encoding genes besides its inhibition of bacterial espionage.

Pathogen hijacks programmed cell death signaling by arginine ADPR-deacylization of caspases

Caspases are evolutionarily conserved cysteine proteases that are essential for regulating cell death and are involved in multiple development and disease processes, including immunity. Here, we show that the bacterial type III secretion system (T3SS) effector CopC (Chromobacterium outer protein C) from the environmental pathogen Chromobacterium violaceum attacks caspase-3/-7/-8/-9 by ADPR-deacylization to dysregulate programmed cell death, including apoptosis, necroptosis, and pyroptosis. This modification involves ADP-ribosylation- and deamination-mediated cyclization on Arg207 of caspase-3 by a mechanism that requires the eukaryote-specific protein calmodulin (CaM), leading to inhibition of caspase activity. The manipulation of cell death signaling by CopC is essential for the virulence of C.violaceum in a mouse infection model. CopC represents a family of enzymes existing in taxonomically diverse bacteria associated with a wide spectrum of eukaryotes ranging from humans to plants. The unique activity of CopC establishes a mechanism by which bacteria counteract host defenses through a previously unrecognized post-translational modification.

Quorum Sensing and Biofilm Disrupting Potential of Imidazole Derivatives in Chromobacterium violaceum Using Antimicrobial and Drug Discovery Approaches.

Population of drug-resistant bacteria have increased at an alarming rate in the past few decades. The major reason for increasing drug resistance is the lack of new antibiotics and limited drug targets. It has therefore been a vital task to develop new antibiotics with different drug targets. Two such targets are biofilm formation and quorum sensing. Quorum sensing is cell to cell communication used by bacteria that initiates many important survival processes and aids in establishing pathogenesis. Both biofilm and quorum sensing are inter-related processes and play a major role in physiological and pathogenesis processes. In this study, five novel imidazole derivatives (IMA-1-IMA-5) were synthesised and tested for their antibacterial and anti-quorum sensing activities against Chromobacterium violaceum using different in silico and in vitro techniques following the standard protocols. In silico results revealed that all compounds were able to effectively bind to and interact sufficiently with the target protein CviR. CviR is a protein to which autoinducers bind to initiate the quorum sensing process. In silico results also revealed that the compounds generated favourable structural dynamics implying that the compounds would be able to effectively bind to CviR and inhibit quorum sensing. Susceptibility results revealed that IMA-1 is the most active of all the derivatives against both planktonic cells and biofilms. Qualitative and quantitative evaluation of anti-quorum sensing activity at sub-inhibitory concentrations of these compounds also revealed high activity for IMA-1. Down-regulation of most of the quorum sensing genes when cells were treated with the test compounds affirmed the high anti-quorum sensing activities of these compounds. The results from this study are promising and urges on the use of anti-quorum sensing and biofilm disrupting molecules to combat multi-drug resistance problem.

Evaluation of anti-biofilm, anti-quorum, anti-dysenteric potential of designed polyherbal formulation: in vitro and in vivo study.

Bacillary dysentery (shigellosis) continues to cause havoc worldwide, with a high infectivity rate. It causes bloody diarrhea, and around 99% of bacillary dysentery cases occur in developing countries. The objective of this study is to develop a polyherbal formulation with the scientific rationale in treating infectious bacillary dysentery disease. The anti-bacterial activity, the minimum inhibitory concentration of the formulation against bacillary dysentery, causing microbes like Shigella flexneri (MTCC 1457), Escherichia coli (MTCC 1687), and Salmonella enterica (MTCC 98), was analysed by well-diffusion method and broth dilution method, respectively. The biofilm inhibition activity was determined on 96 well polystyrene plates and anti-quorum sensing activity by Chromobacterium violaceum CV026. The cytotoxicity was examined by acute oral toxicity. Excreta and organ bacterial load were analyzed by serial dilution method. The formulation efficacy was determined by analyzing the blood sample of rats. The antimicrobial efficacy of the developed formulation was calculated by measuring the zone of inhibition which was found to be 24 mm, 25 mm, and 25 mm, and the MIC values of 1.5 mg/ml, 1.5 mg/ml, and 2.0 mg/ml against S. flexneri, S. enterica, E. coli, respectively. The results show that the polyherbal formulation significantly reduced biofilm formation and has anti-quorum sensing activity. The formulation also effectively decreases the bacterial load and increases the K+, Na+, and Ca++ ions in animals treated with the formulation. The developed formulation was found to be non-toxic and effective against bacillary dysentery; thus, it can be used for treating bacillary dysentery and related complications.

Quorum Quenching Strains Isolated from the Microbiota of Sea Anemones and Holothurians Attenuate Vibriocorallilyticus Virulence Factors and Reduce Mortality in Artemiasalina.

Interference with quorum-sensing (QS) intercellular communication systems by the enzymatic disruption of N-acylhomoserine lactones (AHLs) in Gram-negative bacteria has become a promising strategy to fight bacterial infections. In this study, seven strains previously isolated from marine invertebrates and selected for their ability to degrade C6 and C10-HSL, were identified as Acinetobacter junii, Ruegeria atlantica, Microbulbifer echini, Reinheimera aquimaris, and Pseudomonas sihuiensis. AHL-degrading activity against a wide range of synthetic AHLs were identified by using an agar well diffusion assay and Agrobacterium tumefaciens NTL4 and Chromobacterium violaceum CV026 and VIR07 as biosensors. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis indicated that this activity was not due to an AHL lactonase. All the strains degraded Vibrio coralliilyticus AHLs in coculture experiments, while some strains reduced or abolished the production of virulence factors. In vivo assays showed that strains M3-111 and M3-127 reduced this pathogen’s virulence and increased the survival rate of Artemia salina up to 3-fold, indicating its potential use for biotechnological purposes. To our knowledge, this is the first study to describe AHL-degrading activities in some of these marine species. These findings highlight that the microbiota associated with marine invertebrates constitute an important underexplored source of biological valuable compounds.

The Identification of Chromobacterium violaceum From Soil Based on The Production of Violacein

Chromobacterium violaceum is a purple coloured pathogenic bacterium mainly found in stagnant water and soil. Isolation and identification of this pathogenic bacteria are very important especially in biological science research and clinical field. It was easily identified by the production of purple coloured pigment violacein based on the solubility, colour reaction, spectrophotometry and growth temperature of C. violaceum. The density of C. violaceum found in 5 g of soil was much higher after rainy day which was about 7 X 107 located at 2°59'09.5"N 101°43'33.2"E and 1 X 107 located at 2°58'56.3"N 101°43'15.2"E compared to normal sunny day with only 6 X 105 and 9 X 104 in respectively at the same locations. The soils samples were collected 0-5 cm depth from the soil surface because of the facultative anaerobic where the C. violaceum from underground was more incline go to the top of soil since the concentration of oxygen was higher at the top.

Quorum quenching attenuation of rhizobacteria Chromobacterium violaceum virulence by Desmodium gangeticum root extract

Quorum sensing signal molecules used amongst bacteria for communicating cell density can be interfered with through quenching of the signal molecule, a process known as quorum quenching. Several bacteria depend upon a mechanism generally called as quorum sensing to identify their population density and initiate its colonization. The goal of this research was to test and optimize an anti-quorum sensing chemical derived from Desmodium gangeticum root extract against the biosensor strain Chromobacterium violaceum, a rhizosphere bacterium with an opportunistic pathogenic ability. Desmodium gangeticum root extract contained a chemical known as 1,6-octadien, 3,5-dimethyl-, cis, which had a promising bacterial silencing action. The studies suggested that the extract have a downregulating effect upon bacterial virulence. Response surface modelling (RSM) and the Box-Behnken technique were used to investigate the optimization of dependent variables such as bacterial density, rate of administration, and extract concentration. ANOVA and Cook's distance table were used to verify the mathematical model that resulted. The chemical exhibited anti-quorum sensing activity that is dose dependent, peaking at 300 μg/ml extract three times per day. The findings imply that the extract has no bactericidal effect but does affect the quorum sensing system.

English

South African indigenous plants have been predominantly studied for their antibacterial abilities, overlooking their antipathogenic and antivirulence (also known as antiquorum sensing) potential. Hence, this study explored the selected medicinal plants as possible agents capable of interfering with bacterial growth, quorum sensing and biofilm formation and identified their respective bioactive compounds. Ten medicinal plants were extracted with varied solvents. Melianthus comosus (dichloromethane, aqueous and methanol), Pelargonium sidoides (aqueous) and Vachellia karroo (aqueous and methanol) extracts showed potent minimum inhibitory concentration values ranging from 0.19 to 0.78 mg/ml against the tested bacterial pathogens: Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus pyogenes, and Escherichia coli. Reduced violacein production (up to 38.34%) in Chromobacterium violaceum was noted for Melianthus comosus, Plectranthus ecklonii and Pelargonium sidoides extracts. Treatment of five MDR bacterial pathogens with active extracts for anti-adhesion and biofilm development showed up to 66.34 and 31.82% inhibitory effects, respectively. Chemical characterization of active extracts revealed compounds such as α-D-glucopyranoside, methyl, linalool, octadecanoic acid and hexadecanoic acid. The biological assays validated the tested plant extracts as having antibacterial and antipathogenic potentials that could be used against multidrug resistant bacteria. Key words: Antibacterial activity, biofilm inhibition, chemical characterization, multidrug resistance, phytochemicals, quorum sensing inhibition.

Synthesis and Biological Evaluation of Novel Asymmetric (E)-3-(4-(Benzyloxy) Phenyl)-2-((Substituted Benzylidene) Amino)-1-(Thiazolidin-3-yl) Propan-1-One and Computational Validation by Molecular Docking and QSTR Studies

A novel series of asymmetric of (E)-3-(4-(benzyloxy) phenyl)-2-((substituted benzylidene) amino)-1-(thiazolidin-3-yl) propan-1-one derivatives (AAP-1 to AAP-10) have been efficiently synthesized from (S)-2-amino-3-(4-(benzyloxy)phenyl)-1-(thiazolidin-3-yl)propan-1-one (4) and various substituted aldehydes by conventional as well as microwave irradiation method. The structure of newly synthesized compounds were confirmed by IR, 1H NMR, 13C NMR, and Mass spectroscopic methods, further evaluated for their in vitro antimicrobial activities. Among these series, the compounds AAP-2, AAP-4, AAP-5, AAP-7, AAP-8 AAP-9, and AAP-10, showed excellent antibacterial activities against Gram-positive bacteria like Staphylococcus aureus (SA), Lysinibacillus sphaericus (LS), Bacillus subtilis (BS) and Klebsiella aerogenes (KA), Pseudomonas Aeruginosa (PA), Chromobacterium violaceum (CV) as Gram-negative bacteria as compared to standard Ciprofloxacin. The compounds AAP-1, AAP-4, AAP-5, AAP-6, AAP-7, and AAP-8 exhibited good antifungal activities against Fusarium oxysporum (FO), Rhizoctonia solani (RS), Colletotrichum capsici (CC) strains as compared to standard Fluconazole. Molecular docking studies of final compounds were performed using Auto Dock Vina software against Lanosterol 14α-demethylase (CYP51A1) enzyme and crystal 4WMZ and showed effective binding affinity of these molecules with enzymes. Quantitative structure toxicity relationship study of target compounds were studied by various computational animal models and defined oral rat LD50 values for cytotoxicity. The AAP-2, AAP-4, AAP-5, and AAP-7 to AAP-10 showed low toxicity. In addition, the pharmacokinetic of target compounds were studied and revealed acceptable good drug-likeness score properties as well as follow Lipinski's rule of five.