Antimicrobial potential and in vitro cytotoxicity study of polyvinyl pyrollidone-stabilised silver nanoparticles synthesised from Lysinibacillus boronitolerans

The main emphasis herein is on the eco‐friendly synthesis and assessment of the antimicrobial potential of silver nanoparticles (AgNPs) and a cytotoxicity study. Silver nanoparticles were synthesised by an extracellular method using bacterial supernatant. Biosynthesised silver nanoparticles were characterised by UV‐vis spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, dynamic light scattering, and zeta potential analysis. The synthesised silver nanoparticles exhibited a characteristic peak at 420 nm. TEM analysis depicted the spherical shape and approximately 20 nm size of nanoparticles. Silver nanoparticles carry a charge of −33.75 mV, which confirms their stability. Biogenic polyvinyl pyrrolidone‐coated AgNPs exhibited significant antimicrobial effects against all opportunistic pathogens (Gram‐positive and Gram‐negative bacteria, and fungi). Silver nanoparticles equally affect the growth of both Gram‐positive and Gram‐negative bacteria, with a maximum inhibition zone observed at 22 mm and a minimum at 13 mm against Pseudomonas aeruginosa and Fusarium graminearum, respectively. The minimum inhibitory concentration (MIC) of AgNPs against P. aeruginosa and Staphylococcus aureus was recorded at between 15 and 20 μg/ml. Synthesised nanoparticles exhibited a significant synergistic effect in combination with conventional antibiotics. Cytotoxicity estimates using C2C12 skeletal muscle cell line via 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) test and lactate dehydrogenase assay were directly related to the concentration of AgNPs and length of exposure. On the basis of the MTT test, the IC50 of AgNPs for the C2C12 cell line was approximately 5.45 μg/ml concentration after 4 h exposure.

Antimicrobial activity of PVP coated silver nanoparticles synthesized by Lysinibacillus varians

Emergence of resistant microbes to conventional antibiotics and increased emphasis on health-care costs has raised the concern for the development of new effective antimicrobial reagents. Silver nanoparticles being an excellent broad-spectrum antibacterial agent could be considered as a suitable alternative for existing antibiotic. This study demonstrates the extra-cellular synthesis of stable silver nanoparticles using supernatant of Lysinibacillus varians. The synthesized silver nanoparticles were characterized by using UV-visible spectrum analysis, X-ray diffraction, Transmission electron microscopy (TEM) and FT-IR analysis. The synthesized silver nanoparticles showed a peak around 420 nm. TEM analysis revealed that the size of silver nanoparticles was in the range of 10-20 nm. Silver nanoparticles carry a charge of -39.86 mV, which confirmed the stability of silver nanoparticles. The biologically synthesized silver nanoparticles showed antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. Therefore, the current study reveals an efficient and eco-friendly synthesis of silver nanoparticles by L. varians with potent antimicrobial activity.

Isolation and characterization of chlorpyrifos degrading soil bacteria of environmental and agronomic significance

Chlorpyrifos is being used globally as an agriculture based pesticide. Microbial degrada tion of chlorpyrifos pesticide is of particular interest because of high mammalian toxicity. Six bacterial cultures were isolated from chlorpyrifos contaminated soil by using enrich- ment technique. All the isolates showed good growth in basal salt medium containing chlorpyrifos and suggested their ability to utilize chlorpyrifos as sole carbon and energy source. All the six bacterial cultures were examined for various plant growth promoting properties, out of six only one bacteirial culture Pseudomonas aeruginosa DKC2 was found to be positive for various plant growth promoting activities (phosphate solubiliza- tion, protease activity, IAA production and antagonistic properties against plant patho- genic fungi). The resting cell study confirmed that the bacterial strain DKC2 degrade chlorpyrifos by 71 % within 2 days. Isolated bacterial culture can be used successfully for the removal of chlorpyrifos from contaminated soil along with plant growth promotion, but further research is required before commercial utilization of this isolate in removing chlorpyrifos from contaminated soil.