Jitendra Panwar

A biomimetic approach towards synthesis of zinc oxide nanoparticles

Using natural processes as inspiration, the present study demonstrates a positive correlation between zinc metal tolerance ability of a soil fungus and its potential for the synthesis of zinc oxide (ZnO) nanoparticles. A total of 19 fungal cultures were isolated from the rhizospheric soils of plants naturally growing at a zinc mine area in India and identified on the genus, respectively the species level. Aspergillus aeneus isolate NJP12 has been shown to have a high zinc metal tolerance ability and a potential for extracellular synthesis of ZnO nanoparticles under ambient conditions. UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, and energy dispersive spectroscopy studies further confirmed the crystallinity, morphology, and composition of synthesized ZnO nanoparticles. The results revealed the synthesis of spherical nanoparticles coated with protein molecules which served as stabilizing agents. Investigations on the role of fungal extracellular proteins in the synthesis of nanoparticles indicated that the process is nonenzymatic but involves amino acids present in the protein chains.

Secondary plant metabolites and root exudates: guiding tools for polychlorinated biphenyl biodegradation

Abstract Synthetic organic compounds are hallmark of modern society. They are ubiquitous ranging from home, workplace to agriculture industry, which leads to their non-judicious dispensing into environment. Unfortunately most of them, especially polychlorinated biphenyls (PCBs), are deemed as persistent organic pollutants posing serious health risks to human. Hence, there is an alarming need of phasing out these chemicals and remediating contaminated sites in eco-friendly manner. Phytoremediation has emerged as a highly promising approach which capitalizes on plants and their associated microorganisms for removal of pollutants from targeted sites. Plant root exudations and secondary metabolites efficiently orchestrate selective recruitment of potential PCB-degrading microbial consortia within the rhizosphere and inside plant tissues. Structural analogy between organic contaminants and secondary plant metabolites (SPMEs) renders possible uptake and subsequent degradation of pollutants by microorganisms. Present review is focused on potential role of plant root exudates and SPMEs in structuring and orchestrating remediation of PCBs within rhizosphere and inside plant tissues. Also, recent developments in tools and techniques to study remediation of organic contaminants with special reference to PCBs are addressed.

Removal of Protein Capping Enhances the Antibacterial Efficiency of Biosynthesized Silver Nanoparticles

The present study demonstrates an economical and environmental affable approach for the synthesis of “protein-capped” silver nanoparticles in aqueous solvent system. A variety of standard techniques viz. UV-visible spectroscopy, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) measurements were employed to characterize the shape, size and composition of nanoparticles. The synthesized nanoparticles were found to be homogenous, spherical, mono-dispersed and covered with multi-layered protein shell. In order to prepare bare silver nanoparticles, the protein shell was removed from biogenic nanoparticles as confirmed by UV-visible spectroscopy, FTIR and photoluminescence analysis. Subsequently, the antibacterial efficacy of protein-capped and bare silver nanoparticles was compared by bacterial growth rate and minimum inhibitory concentration assay. The results revealed that bare nanoparticles were more effective as compared to the protein-capped silver nanoparticles with varying antibacterial potential against the tested Gram positive and negative bacterial species. Mechanistic studies based on ROS generation and membrane damage suggested that protein-capped and bare silver nanoparticles demonstrate distinct mode of action. These findings were strengthened by the TEM imaging along with silver ion release measurements using inductively coupled plasma atomic emission spectroscopy (ICP-AES). In conclusion, our results illustrate that presence of protein shell on silver nanoparticles can decrease their bactericidal effects. These findings open new avenues for surface modifications of nanoparticles to modulate and enhance their functional properties.

Nano-fertilizers and Their Smart Delivery System

Outburst of world population in the past decade has forced the agricultural sector to increase crop productivity to satisfy the needs of billions of people especially in developing countries. Widespread existence of nutrient deficiency in soils has resulted in great economic loss for farmers and significant decreases in nutritional quality and overall quantity of grains for human beings and livestock. Use of large-scale application of chemical fertilizers to increase the crop productivity is not a suitable option for long run because the chemical fertilizers are considered as double-edged swords, which on the one hand increase the crop production but on the other hand disturb the soil mineral balance and decrease soil fertility. Large-scale application of chemical fertilizers results in an irreparable damage to the soil structure, mineral cycles, soil microbial flora, plants, and even more on the food chains across ecosystems leading to heritable mutations in future generations of consumers.

Silver triflate catalyzed synthesis of 3-aminoalkylated indoles and evaluation of their antibacterial activities

An efficient, one-pot synthesis was developed for 3-aminoalkylated indoles by three-component coupling reaction of aldehydes, N-methylanilines, and indoles using AgOTf as a catalyst. A series of twenty 3-aminoalkylated indoles was evaluated for their antibacterial activities against both Gram negative and Gram positive bacteria. Compounds 4b and 4r showed good antibacterial activity against both Gram positive and Gram negative strains. However, inversing the property of substituent (from 4r to 4q) resulted in the significant fall in the magnitude of antibacterial activity against Escherichia coli.

Arbuscular Mycorrhizal (AM) Diversity in Prosopis cineraria (L.) Druce under Arid Agroecosystems

Arbuscular mycorrhizal (AM) fungi associated with Prosopis cineraria (Khejri) were assessed for their qualitative and quantitative distribution from eight districts of Rajasthan. A total of three species of Acaulospora, one species of Entrophospora, two species of Gigaspora, twenty-one species of Glomus, seven species of Sclerocystis and three species of Scutellospora were recorded. A high diversity of AM fungi was observed and it varied at different study sites. Among these six genera, Glomus occurred most frequently. Glomus fasciculatum, Glomus aggregatum, and Glomus mosseae were found to be the most predominant AM fungi in infecting Prosopis cineraria. Acaulospora, G. fasciculatum, Sclerocystis was found in all the fields studied, while Scutellospora species were found only in few sites. A maximum of thirty-six AM fungal species were isolated and identified from Jodhpur, whereas only thirteen species were found from Jaisalmer. Spores of Glomus fasciculatum were found to be most abundant under Prosopis cineraria.

Endophytic Nitrogen-Fixing Bacteria as Biofertilizer

Nitrogen is the most limiting nutritional factor for the growth of plants. Since plants cannot reduce atmospheric N2, they require exogenously fixed nitrogen for growth and development. Atmospheric N2 must be first reduced to ammonia to be used by plants. In practice, chemical N fertilizers are used to provide nitrogen nutrition to plants. However, manufacture and use of N fertilizers are associated with environmental hazards that include release of greenhouse gases at the time of manufacture, as well as contamination of underground and surface water due to leaching out of nitrates. Moreover, manufacture of chemical fertilizers requires non-renewable resources like coal and petroleum products. Excess and continuous use of chemical fertilizers to improve the yield of commercial crops has negative effect on soil fertility and reduces their agricultural sustainability. All these concerns necessitate the search for an alternative strategy that can provide nitrogen nutrition to the plants in an efficient and sustainable manner. Here biological nitrogen fixation has immense potential and can be used as an alternate to chemical fertilizers. Biological nitrogen fixation has been reported to be exclusively carried out by few members of the prokaryotic organisms. Biological nitrogen fixation is a process where atmospheric N2 is reduced to NH3. This process is catalyzed by microbial enzyme nitrogenase. Microorganisms having the capacity to fix atmospheric N2 can be used as efficient biofertilizer.

Dimerization of GT element interferes negatively with gene activation

. 1994). The GT elements have a core se-quence rich in A and T, precededby one to two G nucleotideson the 5 side (Zhou 1999). The high degeneracy makes itdifficult to identify them by sequence search. GT elementswere first identified in the pea ribulose 1, 5-biphosphate car-boxylase/oxygenase (Rubisco) small subunit gene (

Efficacy of root-associated fungi and PGPR on the growth of Pisum sativum (cv. Arkil) and reproduction of the root-knot nematode Meloidogyne incognita

The effects of root‐associated fungi (Aspergillus awamori and Glomus mosseae) and plant growth promoting rhizobacteria (PGPR) (Pseudomonas putida, Pseudomonas alcaligenes and Paenibacillus polymyxa) were studied alone and in combination in glasshouse experiments on the growth of pea, enzyme activity (peroxidase and catalase) and reproduction of root‐knot nematode Meloidogyne incognita. Application of A. awamori, G. mosseae and PGPR caused a significant increase in pea growth and enzyme activities of both nematode inoculated and uninoculated plants. A. awamori was more effective in reducing galling and improving the growth of nematode inoculated plants than P. alcaligenes or P. polymyxa. The greatest increase in growth, enzyme activities of nematode‐inoculated plants and reduction in galling and nematode multiplication was observed when A. awamori was used with P. putida or G. mosseae as compared to the other combinations tested. Percentage root colonization was higher when AM fungus inoculated plants were treated with P. putida both in presence and absence of nematode.

Biocontrol of Plant Parasitic Nematodes by Fungi: Efficacy and Control Strategies

Increasing knowledge and growing concern about the elevated cost of inorganic fertilizers or chemical pesticides with their vast applications on various crop plants has raised interest in the alternative method of plant disease protection caused by plant parasitic nematodes. These alternative methods are not only cost-effective but also eco-friendly to the environment and human health. Among the various rhizospheric microorganisms, opportunistic fungi like Paecilomyces lilacinus, Pochonia chlamydosporia, and arbuscular mycorrhizal (AM) fungi have the potential to reduce the severity of diseases caused by plant parasitic nematodes and also improved the plant growth and biomass production. This chapter provides an overview on the biocontrol potential of opportunistic as well as AM fungi on the growth and development of various crop plants. The details about the interactions between these fungi and plant parasitic nematodes have been discussed. An overview of the recent cost-effective technologies used for the mass propagation of these beneficial rhizospheric microorganisms is also discussed.