Metal sensing-carbon dots loaded TiO2-nanocomposite for photocatalytic bacterial deactivation and application in aquaculture.

Nowadays, bioactive nanomaterials have been attracted the researcher's enthusiasm in various fields. Herein, Diplocyclos palmatus leaf extract-derived green-fluorescence carbon dots (DP-CDs) were prepared using the hydrothermal method. Due to the strong fluorescence stability, the prepared DP-CDs were coated on filter-paper to make a fluorometric sensor-strip for Fe3+ detection. After, a bandgap-narrowed DP-CDs/TiO2 nanocomposite (DCTN) was prepared using the methanolic extract of D. palmatus. The prepared DCTN exhibited improved photocatalytic bacterial deactivation under sunlight irradiation. The DCTN-photocatalysis slaughtered V. harveyi cells by the production of reactive oxygen species, which prompting oxidative stress, damaging the cell membrane and cellular constituents. These results suggest the plausible mode of bactericidal action of DCTN-photocatalysis under sunlight. Further, the DCTN has shown potent anti-biofilm activity against V. harveyi, and thereby, DCTN extended the survival of V. harveyi-infected shrimps during the in vivo trial with Litopenaeus vannamei. Notably, this is the first report for the disinfection of V. harveyi-mediated acute-hepatopancreatic necrosis disease (AHPND) using nanocomposite. The reduced internal-colonization of V. harveyi on the hepatopancreas as well as the rescue action of the pathognomonic effect in the experimental animals demonstrated the anti-infection potential of DCTN against V. harveyi-mediated AHPND in aquaculture.

Protective effect of neglected plant Diplocyclos palmatus on quorum sensing mediated infection of Serratia marcescens and UV-A induced photoaging in model Caenorhabditis elegans.

Plants are considered to be a leading source for possible human therapeutic agents. This holistic study has investigated the anti-quorum sensing (anti-QS), anti-infection, antioxidant and anti-photoaging properties of neglected plant Diplocyclos palmatus. The results showed that D. palmatus methanolic leaf extract (DPME) effectively inhibited the quorum sensing (QS) regulated virulence factor production as well as biofilm formation in Serratia marcescens. The transcriptomic analysis revealed that DPME significantly downed the expression of QS-regulated genes such as fimA, fimC, flhC, bsmB, pigP and shlA in S. marcescens, which supports the outcome of in vitro bioassays. Further, the docking study revealed that the presence of active compounds, namely tocopherols and phytol, DPME exhibited its anti-QS activity against S. marcescens. In addition, DPME treatment extended the lifespan of S. marcescens infected C. elegans by the action of dropping the internal accumulation. Further, qPCR analysis clearly revealed that DPME treatment significantly up-regulated the expression of the lifespan-related gene (daf-16) and immune-related genes (clec-60, clec-87, lys-7 and bec-1) in S. marcescens infected C.elegans. On the other hand, DPME extensively reduced the UV-A induced ROS stress, thereby, extended the lifespan in UV-A photoaged C. elegans. Further, the qPCR analysis also confirmed the up-regulation of daf-16, clec-60, clec-87 and col-19 genes which advocated the improvement of the lifespan, healthspan and collagen production in UV-A photoaged C. elegans. Further bioassays evidenced that that the lifespan extension of photoaged C. elegans was accomplished by the actions of antioxidants such as tocopherols and phytol in DPME.

Rapid biosynthesized AgNPs from Gelidiella acerosa aqueous extract mitigates quorum sensing mediated biofilm formation of Vibrio species-an in vitro and in vivo approach.

The present study explores the non-bactericidal anti-virulence efficacy of green synthesized silver nanoparticles (AgNPs) from Gelidiella acerosa against multi-drug resistant Vibrio spp. Spectral characterization of AgNPs was performed through UV-Visible, FT-IR, and energy-dispersive spectroscopic techniques followed by X-ray crystallography and zeta potential analysis. Further, the structural characterization was done by electron and atomic force microscopic techniques. AgNPs profoundly quelled the quorum sensing mediated violacein production in Chromobacterium violaceum and CV026. Characterized AgNPs at 100 µg mL-1 concentrations depicted a phenomenal anti-biofilm efficacy against Vibrio parahaemolyticus (71%) and Vibrio vulnificus (83%) biofilms, which was further confirmed through light, confocal, and scanning electron microscopic analyses. In vitro bioassays revealed the remarkable inhibitory values of AgNPs, by inhibiting the exopolysaccharide production, hydrophobicity, and motility. In vivo studies using Artemia franciscana larvae also confirmed the anti-infective proficiency, as the AgNPs effectively reduced the bacterial colonization and enhanced the survival rate of larvae up to 100% without any toxicity effect. Graphical abstract Rapid biosynthesized AgNPs from Gelidiella acerosa quench quorum sensing controlled virulence traits in vibrios.

In vitro antibiofilm efficacy of Piper betle against quorum sensing mediated biofilm formation of luminescent Vibrio harveyi.

Vibrio harveyi is a potent biofilm former, which confers resistance to multiple antimicrobials, disinfectants, chemicals and biocides. The prevalence of biofilm mediated antibiotic resistance among aquatic bacterial pathogens stresses the search for novel alternative approach to treat vibriosis in aquaculture. Exploring suitable therapeutics from natural resources could be a novel area of research. Therefore, this work was executed to evaluate the inhibitory effect of Piper betle ethyl acetate extract (PBE) on bioluminescence production and biofilm formation of V. harveyi. Minimal inhibitory concentration (MIC) of PBE against planktonic V. harveyi was found to be 1600 µg ml-1; furthermore, PBE inhibited the quorum sensing (QS) mediated bioluminescence production and biofilm formation in V. harveyi upto 98 and 74% respectively, at its sub-MIC concentration of 400 µg ml-1 without affecting their cell viability. Similar results were obtained for exopolysaccharides production and swimming motility related to biofilm formation of V. harveyi, where PBE reduced EPS production upto 64%. Light and confocal laser scanning microscopic analyses further confirmed that the PBE effectively prevented the initial attachment as well as microcolonies formation of V. harveyi biofilm, when compared to their untreated controls. This study demonstrates the promising antibiofilm activity of PBE and confirms the ethnopharmacological potential of this plant against V. harveyi infections.

Antibiofilm activity of Vetiveria zizanioides root extract against methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading human pathogen responsible for causing chronic clinical manifestation worldwide. In addition to antibiotic resistance genes viz. mecA and vanA, biofilm formation plays a prominent role in the pathogenicity of S. aureus by enhancing its resistance to existing antibiotics. Considering the role of folk medicinal plants in the betterment of human health from the waves of multidrug resistant bacterial infections, the present study was intended to explore the effect of Vetiveria zizanioides root on the biofilm formation of MRSA and its clinical counterparts. V. zizanioides root extract (VREX) showed a concentration-dependent reduction in biofilm formation without hampering the cellular viability of the tested strains. Micrographs of scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) portrayed the devastating impact of VREX on biofilm formation. In addition to antibiofilm activity, VREX suppresses the production of biofilm related phenotypes such as exopolysaccharide, slime and α-hemolysin toxin. Furthermore, variation in FT-IR spectra evidenced the difference in cellular factors of untreated and VREX treated samples. Result of mature biofilm disruption assay and down regulation of genes like fnbA, fnbB, clfA suggested that VREX targets these adhesin genes responsible for initial adherence. GC-MS analysis revealed the presence of sesquiterpenes as a major constituent in VREX. Thus, the data of present study strengthen the ethnobotanical value of V. zizanioides and concludes that VREX contain bioactive molecules that have beneficial effect over the biofilm formation of MRSA and its clinical isolates.

Piper betle and its bioactive metabolite phytol mitigates quorum sensing mediated virulence factors and biofilm of nosocomial pathogen Serratia marcescens in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Piper betle, a tropical creeper plant belongs to the family Piperaceae. The leaves of this plant have been well known for their therapeutic, religious and ceremonial value in South and Southeast Asia. It has also been reported to possess several biological activities including antimicrobial, antioxidant, antinociceptive, antidiabetic, insecticidal and gastroprotective activities and used as a common ingredient in indigenous medicines. In Indian system of ayurvedic medicine, P. betle has been well recognized for its antiseptic properties and is commonly applied on wounds and lesions for its healing effects. AIM OF THE STUDY: To evaluate the anti-quorum sensing (anti-QS) and antibiofilm efficacy of P. betle and its bioactive metabolite phytol against Serratia marcescens. MATERIALS AND METHODS: The P. betle ethyl acetate extract (PBE) was evaluated for its anti-QS efficacy against S. marcescens by assessing the prodigiosin and lipase production at 400 and 500µgml-1 concentrations. In addition, the biofilm biomass quantification assay was performed to evaluate the antibiofilm activity of PBE against S. marcescens. Besides, the influence of PBE on bacterial biofilm formation was assessed through microscopic techniques. The biofilm related phenomenons like exopolysaccharides (EPS) production, hydrophobicity and swarming motility were also examined to support the antibiofilm activity of PBE. Transcriptional analysis of QS regulated genes in S. marcescens was also done. Characterization of PBE was done by separation through column chromatography and identification of active metabolites by gas chromatography -mass spectrometry. The major compounds of active fractions such as hexadecanoic acid, eugenol and phytol were assessed for their anti-QS activity against S. marcescens. Further, the in vitro bioassays such as protease, biofilm and HI quantification were also carried out to confirm the anti-QS and antibiofilm potential of phytol in PBE. RESULTS: PBE inhibits QS mediated prodigiosin pigment production in S. marcescens, which confirmed its anti-QS potential against S. marcescens. At 500µgml-1 concentration, PBE significantly inhibited the production of protease, lipase, biofilm and EPS to the level of 71%, 68%, 65% and 43% in S. marcescens, respectively. Further, their antibiofilm efficacy was confirmed through microscopic techniques. In addition, PBE effectively inhibited the hydrophobicity and swarming motility. Additionally, the results of qPCR analysis validated the downregulation of QS genes. Chromatographic techniques the presence of hexadecanoic acid, eugenol and phytol in PBE and the potential bioactive compound with anti-QS activity was identified as phytol. In vitro assays with phytol evidenced the potent inhibition of QS-controlled prodigiosin, protease, biofilm and hydrophobicity in S. marcescens, without exerting any deleterious effect on its growth. CONCLUSION: This study demonstrates the promising anti-QS and antibiofilm activities of PBE and its active metabolite phytol, and confirms the ethnopharmacological applications of these leaves against S. marcescens infections.

Inhibition of biofilm development of uropathogens by curcumin - an anti-quorum sensing agent from Curcuma longa.

Urinary tract infection is caused primarily by the quorum sensing (QS)-dependent biofilm forming ability of uropathogens. In the present investigation, an anti-quorum sensing (anti-QS) agent curcumin from Curcuma longa (turmeric) was shown to inhibit the biofilm formation of uropathogens, such as Escherichia coli, Pseudomonas aeruginosa PAO1, Proteus mirabilis and Serratia marcescens, possibly by interfering with their QS systems. The antibiofilm potential of curcumin on uropathogens as well as its efficacy in disturbing the mature biofilms was examined under light microscope and confocal laser scanning microscope. The treatment with curcumin was also found to attenuate the QS-dependent factors, such as exopolysaccharide production, alginate production, swimming and swarming motility of uropathogens. Furthermore, it was documented that curcumin enhanced the susceptibility of a marker strain and uropathogens to conventional antibiotics.

Antipathogenic potential of Rhizophora spp. against the quorum sensing mediated virulence factors production in drug resistant Pseudomonas aeruginosa.

Quorum sensing (QS) is a process of cell-cell communication mechanism occurs between the bacterial cells through the secretary signal molecules. This QS mechanism has been shown to control over the expression of various genes responsible for the production of virulence factors in several bacterial pathogens. Hence, the present study was intended to evaluate the antipathogenic potential of mangrove trees of the genus Rhizophora against the QS dependent virulence factors production in Pseudomonas aeruginosa PAO1, clinical isolates CI-I (GU447237) and CI-II (GU447238). The methanol extract of Rhizophora apiculata and R. mucronata (1 mg/ml) showed significant inhibition against QS dependent virulence factors production such as LasA protease, LasB elastase, total protease, pyocyanin pigment production and biofilm formation in P. aeruginosa PAO1, CI-I and CI-II. This study for the first time, reports the quorum sensing inhibitory (QSI) potential of Rhizophora spp. against P. aeruginosa infections.

Anti-quorum sensing potential of the mangrove Rhizophora annamalayana.

The present study was carried out to assess the anti-quorum sensing (anti-QS) activity of bark extract obtained from the mangrove plant Rhizophora annamalayana Kathir. against Gram-negative bacteria. In microtitre plate assay, the bark extract at a concentration of 1 mg/ml inhibited the QS-dependent violacein production in Chromobacterium violaceum ATCC 12472. Further, the QS-dependent bioluminescence production in the aquatic bacterial pathogen Vibrio harveyi MTCC 3438 was also reduced to the level of 99 % when treated with the same concentration of the extract. Gas chromatography-mass spectrum analysis identified the presence of seven different chemical constituents, 1H-purin-6-amine, cycloheptasiloxane, cyclooctasiloxane, cyclononasiloxane, cyclononasiloxane octadecamethyl, cyclodecasiloxane eicosamethyl and 1,1,1,5,7,7,7-heptamethyl-3,3-bis(trimethylsiloxy)tetrasiloxane. The molecular docking analysis of the identified compounds revealed that the compounds cyclononasiloxane octadecamethyl and cyclodecasiloxane eicosamethyl exhibited the best docking energy with the QS receptors of C. violaceum and V. harveyi with that of the natural ligand N -hexanoyl- L -homoserine lactone (C6-HSL) and furanosyl borate diester (AI-2). Similarly, another compound 1,1,1,5,7,7,7-heptamethyl-3,3-bis(trimethylsiloxy)tetrasiloxane showed best docking energy only against C6-HSL. Thus, the results of the present study divulge the activity of R. annamalayana bark extract to interfere with bacterial QS.