Inhibition of microbial growth by silver nanoparticles synthesized from Fraxinus xanthoxyloides leaf extract.

AIMS: Conventional antibiotics have been failed to treat infectious diseases due to emergence of multidrug resistance (MDR) in some common pathogens. The current study aimed to formulate new antimicrobials from greener sources. In the midst of these efforts, nanotechnology is a newly emerged field, in which the synthesis of new nanoparticles through novel and efficient means is on the rise. METHODS AND RESULTS: The current work has been carried out to assess the potential of Fraxinus xanthoxyloides (FX) leaf extract in biosynthesis of silver nanoparticles (FX-AgNPs). This method is economical and simple one-step approach to synthesize AgNPs. Characterization of FX-AgNPs has been done by UV-Visible spectroscopy, scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electronic microscope (TEM) and Fourier transforms infrared spectroscopy (FT-IR). The formation of FX-AgNPs has confirmed through UV-Visible spectroscopy (at 430 nm) by change of colour owing to surface Plasmon resonance. Based on the XRD pattern, the crystalline property of FX-AgNPs has established. Functional groups existing in F. xanthoxyloides leaf extract are confirmed by FT-IR spectrum. SEM and TEM authenticated morphology of the AgNPs. The newly synthesized nanoparticles were evaluated for their antimicrobial potential. Minimum inhibitory concentration was determined against Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA) strains, Pseudomonas aeruginosa and Candida albicans by microtiter plate assay. The lowest inhibition (69%) observed against MRSA was at a concentration of 50 ppm FX-AgNPs and maximum inhibition (81%) observed was against P. aeruginosa. The biosynthesized AgNPs triggered up to 68·6% reduction of the P. aeruginosa biofilm when compared to the control. CONCLUSION: It can be concluded that nanoparticles could be a better alternative of antibiotics with greater efficacies and represent a valuable milestone to fight against infections caused by MDR pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: This study imparts a useful insight into the development of a new antimicrobial agent from a novel source.

Atomic-scale 3D imaging of individual dopant atoms in an oxide semiconductor.

The physical properties of semiconductors are controlled by chemical doping. In oxide semiconductors, small variations in the density of dopant atoms can completely change the local electric and magnetic responses caused by their strongly correlated electrons. In lightly doped systems, however, such variations are difficult to determine as quantitative 3D imaging of individual dopant atoms is a major challenge. We apply atom probe tomography to resolve the atomic sites that donors occupy in the small band gap semiconductor Er(Mn,Ti)O3 with a nominal Ti concentration of 0.04 at. %, map their 3D lattice positions, and quantify spatial variations. Our work enables atomic-level 3D studies of structure-property relations in lightly doped complex oxides, which is crucial to understand and control emergent dopant-driven quantum phenomena.

Enhanced biodegradation and emulsification of crude oil and hyperproduction of biosurfactants by a gamma ray-induced mutant of Pseudomonas aeruginosa.

A gamma ray-induced mutant of Pseudomonas aeruginosa strain S8, capable of hyperproduction of biosurfactant from hydrocarbons, was isolated and named as EBN-8. The mutant showed 3-4 times more hydrocarbon emulsification/conversion as compared to the parent when grown on Khaskheli crude oil in minimal medium. Enhanced biosurfactant production and hydrocarbon utilization by the mutant was also observed during growth on heptadecane in minimal medium as indicated by emulsion index and surface tension of cell-free culture broth. Using heptadecane as carbon and energy source, time course for the growth (cfu ml-1) and biosurfactant production were compared for both parent and mutant. These studies were carried out for 24 d at 30 +/- 2 degrees C and for 20 d at 37 degrees C. Growth of EBN-8 was much faster compared to the parent as well as being 2-3 times more hyperproductive.