Neeta Sharma

Bio: Neeta Sharma is an academic researcher from University of Lucknow. The author has contributed to research in topics: Essential oil & Spore germination. The author has an hindex of 11, co-authored 35 publications receiving 948 citations.

Fungitoxicity of the essential oil of Citrus sinensis on post-harvest pathogens

Abstract: The essential oil extracted from the epicarp of Citrus sinensis exhibited absolute fungitoxicity against the 10 post-harvest pathogens. GC–MS studies of the oil revealed the presence of 10 chemical constituents, of which limonene was found to be the major component (84.2%). The activity of the oil was tested by the poisoned food technique (PF) and the volatile activity (VA) assay and the oils showed greater toxicity in the VA assay than in the poisoned food assay. The nature of the toxicity was studied in the VA assay and it was observed that the oil was fungicidal for the 10 pathogens in the 700 ppm (mg/l) to 1000 ppm range. The oil was extremely toxic for spore germination and it was found that at 700 ppm, spore germination was inhibited in the 10 test fungi out of the 12 tested. Treatment at 300 ppm concentration exhibited 70–100% inhibition of spore germination in most of the fungi tested. Scanning electron microscopy (SEM) was done to study the mode of action of the oil in Aspergillus niger and it was observed that treatment with the oil leads to distortion and thinning of the hyphal wall and the reduction in hyphal diameter and absence of conidiophores.

Studies on nano-CaO·SnO 2 and nano-CaSnO 3 as anodes for Li-ion batteries

Abstract: The nanocomposite "CaO·SnO 2 " and nano-CaSnO 3 are prepared by the thermal decomposition of CaSn(OH) 6 precursor and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HR-TEM) along with selected area electron diffraction (SAED) and density measurements. Nanosize (3-6 nm) grains of CaO and SnO 2 in the X-ray amorphous CaO·SnO 2 and particles of ~60 nm size in nano-CaSnO 3 are obtained. Galvanostatic cycling of both the phases vs Li metal is performed in the voltage ranges 0.005-1.0 V and 0.005-1.3 V at the current rate, 60 mA g −1 (0.12 C). Stable and reversible capacities of 490 (±5) and 550 (±5) mA h g −1 are observed for nano-CaO·SnO 2 respectively up to 50 cycles in the above voltage windows. These values correspond to 3.8 and 4.2 mol of cyclable Li per mole of CaO·SnO 2 in comparison to the theoretical value of 4.4 mol of Li. A capacity of 420 (±5) mA h g −1 is observed at a rate of 0.4 C. Nano-CaSnO 3 showed a stable capacity of 445 (±5) mA h g −1 (3.4 moles of Li) up to 50 cycles when cycled in the voltage window, 0.005-1.0 V. The average discharge and charge potentials are 0.2 V and 0.5 V, respectively, for both the phases. The reasons for the superior Li-cycling performance of nano-CaO·SnO 2 in comparison to nano-CaSnO 3 are discussed. Ex situ XRD, TEM, and SAED studies are carried out to support the reaction mechanism. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) data as a function of voltage are presented and discussed to complement the galvanostatic results. The "apparent" Li-ion diffusion coefficient (D Li+ ) estimated from EIS is ~1.0 × 10 −14 cm 2 s −1 at V ≤ 1.0 V during the first cycle and 11th discharge cycle.

Isolation and characterization of Staphylococcus sp. strain NBRIEAG-8 from arsenic contaminated site of West Bengal

Abstract: Arsenic contaminated rhizospheric soils of West Bengal, India were sampled for arsenic resistant bacteria that could transform different arsenic forms. Staphylococcus sp. NBRIEAG-8 was identified by16S rDNA ribotyping, which was capable of growing at 30,000 mg l−1 arsenate [As(V)] and 1,500 mg l−1 arsenite [As(III)]. This bacterial strain was also characterized for arsenical resistance (ars) genes which may be associated with the high-level resistance in the ecosystems of As-contaminated areas. A comparative proteome analysis was conducted with this strain treated with 1,000 mg l−1 As(V) to identify changes in their protein expression profiles. A 2D gel analysis showed a significant difference in the proteome of arsenic treated and untreated bacterial culture. The change in pH of cultivating growth medium, bacterial growth pattern (kinetics), and uptake of arsenic were also evaluated. After 72 h of incubation, the strain was capable of removing arsenic from the culture medium amended with arsenate and arsenite [12% from As(V) and 9% from As(III)]. The rate of biovolatilization of As(V) was 23% while As(III) was 26%, which was determined indirectly by estimating the sum of arsenic content in bacterial biomass and medium. This study demonstrates that the isolated strain, Staphylococcus sp., is capable for uptake and volatilization of arsenic by expressing ars genes and 8 new upregulated proteins which may have played an important role in reducing arsenic toxicity in bacterial cells and can be used in arsenic bioremediation.

Potential antimicrobial uses of essential oils in food: is citrus the answer?

Abstract: The antimicrobial properties of essential oils (EOs) have been recognised for centuries and, with growing demand from changes in legislation, consumer trends and increasing isolation of antibiotic resistant pathogens, alternatives to chemical-based bactericides need to be found. Citrus oils not only lend themselves to use in food but also are generally recognised as safe (GRAS) and have been found to be inhibitory both in direct oil and vapour form against a range of both Gram-positive and Gram-negative bacteria. This group of oils may provide the natural antimicrobials that the food industry requires to fulfil both its requirements and those of the consumer.

Abiotic stress responses and microbe-mediated mitigation in plants: The omics strategies

Abstract: Abiotic stresses are the foremost limiting factors for agricultural productivity. Crop plants need to cope up adverse external pressure created by environmental and edaphic conditions with their intrinsic biological mechanisms, failing which their growth, development, and productivity suffer. Microorganisms, the most natural inhabitants of diverse environments exhibit enormous metabolic capabilities to mitigate abiotic stresses. Since microbial interactions with plants are an integral part of the living ecosystem, they are believed to be the natural partners that modulate local and systemic mechanisms in plants to offer defence under adverse external conditions. Plant-microbe interactions comprise complex mechanisms within the plant cellular system. Biochemical, molecular and physiological studies are paving the way in understanding the complex but integrated cellular processes. Under the continuous pressure of increasing climatic alterations, it now becomes more imperative to define and interpret plant-microbe relationships in terms of protection against abiotic stresses. At the same time, it also becomes essential to generate deeper insights into the stress-mitigating mechanisms in crop plants for their translation in higher productivity. Multi-omics approaches comprising genomics, transcriptomics, proteomics, metabolomics and phenomics integrate studies on the interaction of plants with microbes and their external environment and generate multi-layered information that can answer what is happening in real-time within the cells. Integration, analysis and decipherization of the big-data can lead to a massive outcome that has significant chance for implementation in the fields. This review summarizes abiotic stresses responses in plants in-terms of biochemical and molecular mechanisms followed by the microbe-mediated stress mitigation phenomenon. We describe the role of multi-omics approaches in generating multi-pronged information to provide a better understanding of plant-microbe interactions that modulate cellular mechanisms in plants under extreme external conditions and help to optimize abiotic stresses. Vigilant amalgamation of these high-throughput approaches supports a higher level of knowledge generation about root-level mechanisms involved in the alleviation of abiotic stresses in organisms.