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Application of nanotechnology for the synthesis of silver nanoparticles using plant extract can be a promising alternative to traditional chemical methods. Products of biological origin have less side effects, thus are safe for human health besides being cost-effective and pollution-free. Keeping in view this, the current work was designed for the environment-friendly production of silver nanoparticles (AgNPs) utilising Isodon coetsa acetone leaf extract. The effect of some important variables including incubation time, pH, AgNO3 concentration, temperature and volume of plant extract were examined for the optimum production of AgNPs. Synthesized nanoparticles were further characterized using atomic force microscopy (AFM), X-ray diffraction spectroscopy (XRD), and UV-visible absorption spectroscopy. In addition, the antibacterial potential of nanoparticles was also determined by agar-well diffusion method. The optimal conditions for synthesis of AgNPs achieved after 24 h of incubation at pH 9.0, 2mM AgNO3, 60°C temperature, and using 10% I. coetsa leaf extract. X-ray diffraction spectroscopy revealed that the size of the strongest peak for AgNPs was 9.5 nm, while atomic force microscopy confirmed their spherical shape with smooth surface without any pinholes or cracks. AgNPs showed excellent antibacterial action against Gram-positive and Gram-negative bacteria. The current study has contributed to the development of a simple and fast bioprocess for the synthesis of AgNPs of the appropriate size and form which also have increased antibacterial activity in comparison to crude extract. Therefore, the process of biogenically synthesised AgNPs from plants is a straightforward, commercially feasible, and environmentally benign approach that can be used in disease control while utilizing their important role as therapeutic agent for treating various ailments caused by pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Multifarious plant growth-promoting Bacillus strains recovered from rhizospheric soils of the Indo Gangetic plains (IGPs) were identified as Bacillus licheniformis MNNITSR2 and Bacillus velezensis MNNITSR18 based on their biochemical characteristics and 16S rDNA gene analysis. Both strains exhibited the ability to produce IAA, siderophores, ammonia, lytic enzymes, HCN production, and phosphate solubilization capability and strongly inhibited the growth of phytopathogens such as Rhizoctonia solani and Fusariun oxysporum in vitro. In addition, these strains are also able to grow at a high temperature of 50 °C and tolerate up to 10–15% NaCl and 25% PEG 6000. The results of the pot experiment showed that individual seed inoculation and the coinoculation of multifarious plant growth promoting (PGP) Bacillus strains (SR2 and SR18) in rice fields significantly enhanced plant height, root length volume, tiller numbers, dry weight, and yield compared to the untreated control. This indicates that these strains are potential candidates for use as PGP inoculants/biofertilizers to increase rice productivity under field conditions for IGPs in Uttar Pradesh, India. [ABSTRACT FROM AUTHOR]

An investigation was carried out with bulk and pigeonpea rhizosphere soils collected from Middle Gangetic region of Uttar Pradesh (UP). Collected soils were analyzed for physicochemical characteristics, bacterial population and R/S ratio. In the present study, bacterial count of rhizosphere soils were found to range between 250x105 to 40x105 whereas in bulk soil ranging from 220x105 to 14x105. The R/S ratio ranging from 5.74 to 1.12, indicating positive rhizospheric effect in collected soil samples. In addition, bacterial population associated with bulk and pigeonpea rhizosphere soils were also evaluated in vitro plant growth promoting attributes. In the present investigation, 46%, 16.6%, 75% and 21% of bacterial population associated with rhizosphere soil were found to be phosphate solubilizing, IAA, siderophore and HCN producing respectively whereas in bulk soil 5.5%, 38.8% and 67% of bacterial population were found to be phosphate solubilizing, IAA and siderophore producing respectively. The results suggest that higher percentage of phosphate solubilizers, IAA, siderophore and HCN producers were found in rhizospheric soils of pigeonpea as comparison to bulk soils and may be exploited as biofertilizers or microbial inoculants in the soils of pigeon pea crops growing in the vicinity of middle Gangetic region of Uttar Pradesh. [ABSTRACT FROM AUTHOR]

Plant-based synthesis of nanoparticles has generated worldwide interest because of cost-effectiveness, eco-friendly nature and plethora of applications. In the present investigation, antimicrobial potential of silver nanoparticles (AgNPs) of methanolic extract of Aegle marmelos fruit has been investigated. Agar well diffusion method was used for determining antimicrobial activity of solvent extracts ( viz ., petroleum ether, chloroform, acetone, methanol and aqueous), and AgNPs. Among these, methanolic extract of A. marmelos showed highest inhibitory activity against B. cereus (16.17 ± 0.50 mm) followed by P. aeruginosa (13.33 ± 0.62 mm) and E. coli . Phytochemical analysis of methanolic extract of A. marmelos revealed the presence of tannins, saponins, steroids, alkaloids, flavonoids, and glycosides. AgNPs synthesized using A. marmelos methanolic extract, characterized by UV-Visible spectroscopy, atomic force microscopy, dynamic light scattering, and X-ray diffraction showed a peak at 436 nm and size ranged between 159 and 181 nm. Evaluation of the antimicrobial potential of green synthesized AgNPs recorded the highest inhibitory activity against B. cereus (19.25 ± 0.19 mm) followed by P. aeruginosa (16.50 ± 0.30 mm) and S. dysentriae . The minimum inhibitory concentration (MIC) of synthesized AgNPs was found to be in the range of 0.009875-0.0395 mg/100 μl which was quite lower than the MIC of crude extract i.e. 0.0781-0.3125 mg/100 μl. The results obtained indicated that the different crude extracts of A. marmelos plant as well as AgNPs have a strong and effective antimicrobial potential that provide a marvelous source for the development of new drug molecules of herbal origin which may be used for the welfare of humanity., (© 2020 Center for Food and Biomolecules, National Taiwan University. Production and hosting by Elsevier Taiwan LLC.)