Biogenic nanoparticles bearing antibacterial activity and their synergistic effect with broad spectrum antibiotics: Emerging strategy to combat drug resistant pathogens

AbstractThe present study emphasizes on synthesis of bimetallic silver–gold nanoparticles from cell free supernatant of Pseudomonas veronii strain AS41G inhabiting Annona squamosa L. The synthesized nanoparticles were characterized using hyphenated techniques with UV–Visible spectra ascertained absorbance peak between 400 and 800nm. Possible interaction of biomolecules in mediating and stabilization of nanoparticles was depicted with Fourier transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) displayed Bragg’s peak conferring the 100, 111, 200, and 220 facets of the face centered cubic symmetry of nanoparticles suggesting that these nanoparticles were crystalline in nature. Size and shape of the nanoparticles were determined using Transmission electron microscopy (TEM) microgram with size ranging from 5 to 50nm forming myriad shapes. Antibacterial activity of nanoparticles against significant human pathogens was conferred with well diffusion assay and its synergistic effect with standard antibiotics revealed 87.5% fold increased activity with antibiotic “bacitracin” against bacitracin resistant strains Bacillus subtilis, Escherichia coli and Klebsiella pneumoniae followed by kanamycin with 18.5%, gentamicin with 11.15%, streptomycin with 10%, erythromycin with 9.7% and chloramphenicol with 9.4%. Thus the study concludes with biogenic and ecofriendly route for synthesizing nanoparticles with antibacterial activity against drug resistant pathogens and attributes growing interest on endophytes as an emerging source for synthesis of nanoparticles

Endo-symbiont mediated synthesis of gold nanobactericides and their activity against human pathogenic bacteria

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Synthesis of gold nanobactericides (AuNBs) were achieved by treating 1 mM chloroaurate with cell free supernatant of Aneurinibacillus migulanus. Formation of AuNBs was initially was monitored with change in colour to ruby red. Further confirmation was assessed with UV–visible spectra with maximum absorption occurring at 510 nm. Transmission electron microscopy (TEM) analysis revealed the polydispersity of AuNBs with size distribution ranging from 10 to 60 nm with an average size of 30 nm. Crystalline nature was studied using X-ray diffraction which exhibited characteristic peaks indexed to Bragg's reflection at 2θ angle which confers (111), (200), (220), and (311) planes suggesting AuNBs were face-centred cubic. Fourier transform infrared spectroscopy (FTIR) analysis revealed absorption peaks occurring at 3341 cm⁠−1, 1635 cm⁠−1 and 670 cm⁠−1 which corresponds to functional groups attributing to synthesis. The antibacterial efficacy of AuNBs was tested against selective human pathogenic bacteria and activity was measured as zone of inhibition by using disc and well diffusion. Bactericidal activity was interpreted with standard antibiotics gentamicin and kanamycin. Micro broth dilution assay expressed the minimal concentration of AuNBs to inhibit the growth of test pathogens. Highest activity was observed against Pseudomonas aeruginosa (MTCC 7903) with 21.00 ± 0.57 mm compared to other pathogens. The possible mode of action of AuNBs on DNA was carried out with in vitro assay as preliminary test against pathogenic DNA isolated from P. aeruginosa. Further studies will be interesting enough to reveal the exact interactive mechanism of AuNBs with DNA. Overall study contributes towards biogenic synthesis of AuNBs as one of the alternative in combating drug resistant pathogens

Plants: Emerging as Nanofactories towards Facile Route in Synthesis of Nanoparticles

Plant mediated nanoparticles’ synthesis has led to a remarkable progress via unfolding a green synthesis protocol towards nanoparticles’ synthesis. It seems to have drawn quite an unequivocal attention with a view of reformulating the novel strategies as alternatives for popular conventional methods. Hence, the present review summarizes the literature reported thus far and envisions towards plants as emerging sources of nanofactories

Bioactivity-guided isolation of antimicrobial metabolite from Xylaria sp.

Symbiotic plant-microbe metabolic interactions not only have beneficial effects on plants but also contribute to rich, unmatched and complex chemical biodiversity with biological potential. Systematic delineated bioprospecting of fungal diversity associated with Ficus pumila Linn (Moraceae) for antimicrobial metabolite revealed Xylaria sp. FPL-25(M). The present study describes bioactivity guided fractionation prioritized for antimicrobial potential. Thus, chemical investigation of culture broth of Xylaria sp. FPL-25(M) by bioactivity guided fractionation with spectroscopic techniques revealed bioactive metabolite xylobovide-9-methyl ester. The xylobovide-9-methyl ester exhibited broad-spectrum antimicrobial activity. However, Gram-positive bacteria and fungi were more susceptible than Gram-negative bacteria. The present study results represent bioassay-based screening strategy which facilitates rapid, efficient and reliable approach for endophytic strain prioritization for novel bioactive molecules

Phylogenetic tree derived from NJ analysis showing the evolutionary relationship of <i>Emericella variecolor</i> CLB38 with its closest BLAST hits.

<p>Bootstrap values (1000 replications) based on multiple sequence alignment using the MEGA-5 software. Asterisk indicates the isolate obtained in this study.</p

Application of Bioassay-Guided Fractionation Coupled with a Molecular Approach for the Dereplication of Antimicrobial Metabolites

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.A systematically delineated dereplication approach was described based on genome mining and bioassay-guided fractionation using endophytic fungus Xylaria psidii FPL-52(S) isolated from leaves of Ficus pumila Linn., (Moraceae). A polyketide synthase gene-based molecular screening strategy by a degenerate oligonucleotide primer polymerase chain reaction technique coupled with a bioinformatic phylogenomic approach revealed the presence of an iterative polyketide synthase gene within the genome of Xylaria psidii FPL-52(S). Chemical dereplication of ethyl acetate extract derived from a submerged fermentation culture broth of Xylaria psidii FPL-52(S) by bioassay-guided chromatographic and hyphenated analytical spectroscopic techniques led to the identification of polyketide mycoalexin 3-O-methylmellein. Antimicrobial profiling and minimal inhibitory concentration values for 3-O-methylmellein were determined by disc diffusion and microbroth dilution techniques. Gram-positive bacteria, dermatophytic and phytopathogenic fungi were susceptible in terms of inhibition zone and minimum inhibitory concentration values when compared to co-assayed standards. Herein, we highlight and demonstrate an improved approach which facilitates efficient dereplication and effect-guided fractionation of antimicrobial metabolite(s). The present work flow serves as a promising dereplication tool to survey the biosynthetic potential of endophytic fungal diversity, thereby identifying the most promising strains and prioritizing them for novel polyketide-derived antimicrobial metabolite discovery

Minimum inhibitory concentration (MIC in μg/ml) of purified compound Emerimidine A from endosymbiotic <i>E</i>. <i>variecolor</i> CLB38 against test microorganisms.

<p>Minimum inhibitory concentration (MIC in μg/ml) of purified compound Emerimidine A from endosymbiotic <i>E</i>. <i>variecolor</i> CLB38 against test microorganisms.</p

PCR amplification of rDNA from <i>Emericella variecolor</i> CLB38 using ITS1 and ITS4 universal primers.

<p>Lane: M—100 bp DNA ladder; CLB38 –~575 bp amplicon representing ITS region of rDNA; C–control.</p

Application of Bioassay-Guided Fractionation Coupled with a Molecular Approach for the Dereplication of Antimicrobial Metabolites

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.A systematically delineated dereplication approach was described based on genome mining and bioassay-guided fractionation using endophytic fungus Xylaria psidii FPL-52(S) isolated from leaves of Ficus pumila Linn., (Moraceae). A polyketide synthase gene-based molecular screening strategy by a degenerate oligonucleotide primer polymerase chain reaction technique coupled with a bioinformatic phylogenomic approach revealed the presence of an iterative polyketide synthase gene within the genome of Xylaria psidii FPL-52(S). Chemical dereplication of ethyl acetate extract derived from a submerged fermentation culture broth of Xylaria psidii FPL-52(S) by bioassay-guided chromatographic and hyphenated analytical spectroscopic techniques led to the identification of polyketide mycoalexin 3-O-methylmellein. Antimicrobial profiling and minimal inhibitory concentration values for 3-O-methylmellein were determined by disc diffusion and microbroth dilution techniques. Gram-positive bacteria, dermatophytic and phytopathogenic fungi were susceptible in terms of inhibition zone and minimum inhibitory concentration values when compared to co-assayed standards. Herein, we highlight and demonstrate an improved approach which facilitates efficient dereplication and effect-guided fractionation of antimicrobial metabolite(s). The present work flow serves as a promising dereplication tool to survey the biosynthetic potential of endophytic fungal diversity, thereby identifying the most promising strains and prioritizing them for novel polyketide-derived antimicrobial metabolite discovery