Isolation and characterization of halotolerant plant growth promoting rhizobacteria from mangrove region of Sundarbans, India for enhanced crop productivity.

Halotolerant plant growth promoting rhizobacteria (PGPR) are beneficial microorganisms utilized to mitigate the biotic and abiotic stresses in plants. The areas of Sundarban mangroves of West Bengal, India have been reported to be rich in halotolerant microflora, yet major area remains unexplored. The present study, therefore, aims to map down the region-specific native microbial community potent of salt tolerance, plant growth promoting (PGP) activity and antagonistic activity against fungal pathogens. Bacterial samples were isolated from the saline soil of the Sundarban mangroves. A total of 156 bacterial samples were isolated and 20 were screened for their salt tolerance potential. These isolates were characterised using morphological, biochemical, and molecular approaches. Based on 16s rRNA sequencing, they were classified into 4 different genera, including Arthrobacter sp. (01 isolate), Pseudomonas plecoglossicida (01 isolate), Kocuria rosea (01 isolate), and Bacillus (17 isolates). The halotolerant isolates which possessed plant growth promoting traits including phosphate, and zinc solubilization, indole acetic acid production, siderophore, and ammonia generation were selected. Further, the effect of two halotolerant isolates GN-5 and JR-12 which showed most prominent PGP activities was evaluated in pea plant under high salinity conditions. The isolates improved survival by promoting germination (36 to 43%) and root-shoot growth and weight of pea plant in comparison to non-inoculated control plants. In a subsequent dual culture confrontation experiment, both these halo-tolerant isolates showed antagonistic activities against the aggressive root rot disease-causing Macrophomina phaseolina (Tassi) Goid NAIMCC-F-02902. The identified isolates could be used as potential bioagents for saline soils, with potential antagonistic effect on root rot disease. However, further studies at the physiological and molecular level would help to delineate a detail mechanistic understanding of broad-spectrum defence against salinity and potential biotic pathogen.

NMR-Based Metabolomic Imprinting Elucidates Macrophage Polarization of THP-1 Cell Lines Stimulated by Zinc Oxide Nanoparticles.

Zinc oxide (ZnO) nanoparticles (NPs) have been widely used in industry, cosmetics, drugs, bioimaging, and drug delivery. ZnO NPs have been found to interact and interfere with cellular physiology via macrophages, thereby resulting in macrophage polarization. The functional reprogramming of the cells is synchronized through cellular metabolic adaptations. The current study, therefore, aims to establish crosstalk between ZnO-NP-induced metabolic alterations and macrophage polarization in PMA-activated THP-1 cell lines. We observed moderate to heightened cytotoxic response in terms of cell viability and proliferation. The results also revealed increased Th1-type cytokine and chemokine expression. In order to characterize the changes in metabolite concentration in treatment groups, we employed multivariate data analysis (principal component analysis and partial least-squares discriminant analysis) of 1H NMR spectra. The results revealed biologically relevant patterns and alterations in many metabolic pathways. These alterations and patterns were found to be in line across the immune-cytotoxic axis. Furthermore, the results also implicate the role of carbon metabolism toward the classical activation of macrophage polarization. The omics approach could identify the markers involved in NP-induced toxicity, thus elaborating our vision of cytotoxicity that is currently limited to end-point and cytokine assays. Also, it could be emphasized that metabolic reconfiguration upon NP stimulation could direct macrophage polarization toward classical activation.

Managing arsenic (V) toxicity by phosphate supplementation in rice seedlings: modulations in AsA-GSH cycle and other antioxidant enzymes.

The toxic and non-essential metalloid arsenic (As) is ubiquitous in the environment with its absorption from the soil into the plants' roots posing detrimental effects on the crop plants and hence the food availability and food security are also threatened. The present study was intended to reduce the As-induced toxicity in rice seedlings (Oryza sativa L.) by phosphate (PO43-). For this, three concentrations of potassium phosphate (KH2PO4), 50, 100 and 150 µM were supplemented along with 50 µM As exposure to hydroponically grown 7-day-old rice seedlings. Supplementation of PO43- significantly recovered arsenic-induced diminutions in growth parameters and photosynthetic pigment contents which were due to the significant increase in superoxide radical (SOR, O2•¯) and hydrogen peroxide (H2O2). Supplementation of 50 µM PO43- could significantly increase the activity of APX (ascorbate peroxidase) and GR (glutathione reductase) while 100 µM PO43- could increase the activity of DHAR (dehydroascorbate reductase) and monodehydroascorbate reductase (MDHAR). As the amount of PO43- was increased, the ratio of AsA/DHA (reduced to oxidized ascorbate) and GSH/GSSG (reduced to oxidized glutathione) was increased significantly due to increase in the reduced form of the non-enzymes i.e. AsA and GSH. The activity of SOD (superoxide dismutase) and GPX (guaiacol peroxidase) decreased significantly after a substantive increase in their activities due to As stress while the CAT (catalase) activity further enhanced after the supplementation of 50 and 100 µM PO43-. Thus, the As-induced oxidative stress in the rice seedlings was managed by concerted modulations in the activities of SOD, GPX, CAT and AsA-GSH cycle enzymes and metabolites.

Sparsity-based nonlinear reconstruction of optical parameters in two-photon photoacoustic computed tomography.

We present a new nonlinear optimization approach for the sparse reconstruction of single-photon absorption and two-photon absorption coefficients in the photoacoustic computed tomography (PACT). This framework comprises of minimizing an objective functional involving a least squares fit of the interior pressure field data corresponding to two boundary source functions, where the absorption coefficients and the photon density are related through a semi-linear elliptic partial differential equation (PDE) arising in PAT. Further, the objective functional consists of an L 1 regularization term that promotes sparsity patterns in absorption coefficients. The motivation for this framework primarily comes from some recent works related to solving inverse problems in acousto-electric tomography and current density impedance tomography. We provide a new proof of existence and uniqueness of a solution to the semi-linear PDE. Further, a proximal method, involving a Picard solver for the semi-linear PDE and its adjoint, is used to solve the optimization problem. Several numerical experiments are presented to demonstrate the effectiveness of the proposed framework.

Sparse reconstruction of log-conductivity in current density impedance tomography.

A new non-linear optimization approach is proposed for the sparse reconstruction of log-conductivities in current density impedance imaging. This framework comprises of minimizing an objective functional involving a least squares fit of the interior electric field data corresponding to two boundary voltage measurements, where the conductivity and the electric potential are related through an elliptic PDE arising in electrical impedance tomography. Further, the objective functional consists of a L 1 regularization term that promotes sparsity patterns in the conductivity and a Perona-Malik anisotropic diffusion term that enhances the edges to facilitate high contrast and resolution. This framework is motivated by a similar recent approach to solve an inverse problem in acousto-electric tomography. Several numerical experiments and comparison with an existing method demonstrate the effectiveness of the proposed method for superior image reconstructions of a wide-variety of log-conductivity patterns.

Nanomaterials and microbes' interactions: a contemporary overview.

Use of nanomaterials in the field of science and technology includes different fields in food industry, medicine, agriculture and cosmetics. Nanoparticle-based sensors have wide range of applications in food industry for identification and detection of chemical contaminants, pathogenic bacteria, toxins and fungal toxins from food materials with high specificity and sensitivity. Nanoparticle-microbe interactions play a significant role in disease treatment in the form of antimicrobial agents. The inhibitory mechanism of nanoparticles against different bacteria and fungi includes release of metal ions that interacts with cellular components through various pathways including reactive oxygen species (ROS) generation, pore formation in cell membranes, cell wall damage, DNA damage, and cell cycle arrest and ultimately inhibits the growth of cells. Nanoparticle-based therapies are growing to study the therapeutic treatments of plant diseases and to prevent the growth of phytopathogens leading to the growing utilization of engineered nanomaterials. Hence, with this background, the present review focuses thoroughly on detailed actions and responses of nanomaterials against different bacteria and fungi as well as food sensing and storage.

Reactive oxygen species signaling and stomatal movement: Current updates and future perspectives.

Reactive oxygen species (ROS), a by-product of aerobic metabolism were initially studied in context to their damaging effect but recent decades witnessed significant advancements in understanding the role of ROS as signaling molecules. Contrary to earlier views, it is becoming evident that ROS production is not necessarily a symptom of cellular dysfunction but it might represent a necessary signal in adjusting the cellular machinery according to the altered conditions. Stomatal movement is controlled by multifaceted signaling network in response to endogenous and environmental signals. Furthermore, the stomatal aperture is regulated by a coordinated action of signaling proteins, ROS-generating enzymes, and downstream executors like transporters, ion pumps, plasma membrane channels, which control the turgor pressure of the guard cell. The earliest hallmarks of stomatal closure are ROS accumulation in the apoplast and chloroplasts and thereafter, there is a successive increase in cytoplasmic Ca2+ level which rules the multiple kinases activity that in turn regulates the activity of ROS-generating enzymes and various ion channels. In addition, ROS also regulate the action of multiple proteins directly by oxidative post translational modifications to adjust guard cell signaling. Notwithstanding, an active progress has been made with ROS signaling mechanism but the regulatory action for ROS signaling processes in stomatal movement is still fragmentary. Therefore, keeping in view the above facts, in this mini review the basic concepts and role of ROS signaling in the stomatal movement have been presented comprehensively along with recent highlights.

Metal accumulation, growth, antioxidants and oil yield of Brassica juncea L. exposed to different metals.

In agricultural fields, heavy metal contamination is responsible for limiting the crop productivity and quality. This study reports that the plants of Brassica juncea L. cv. Pusa bold grown on contaminated substrates [Cu, Cr(VI), As(III), As(V)] under simulated field conditions have shown translocation of metals to the upper part and its sequestration in the leaves without significantly affecting on oil yield, except for Cr and higher concentration of As(V), compared to control. Decrease in the oil content in As(V) treated plants was observed in a dose dependent manner; however, maximum decrease was recorded in Cr treated plants. Among all the metal treatments, Cr was the most toxic as evident from the decrease in oil content, growth parameters and antioxidants. The accumulation of metals was below the detection limit in the seeds grown on 10 and 30 mg kg(-1) As(III) and Cr(VI); 10 mg kg(-1) As(V)) and thus can be recommended only for oil cultivation.

Studies on antidermatophytic activity of waste leaves of Curcuma longa L.

During antidermatophytic screening of some essential oils, Curcuma longa L. exhibited the strongest antifungal activity, completely inhibiting the mycelial growth of ringworm, caused by the fungi- Microsporum gypseum and Trichophyton mentagrophytes. The essential oil from leaves of Curcuma longa was fungicidal at 2.5 µl/ml at which it tolerated heavy doses of inoculum. The fungicidal activity of the oil was thermostable up to 80 °C and self life up to 24 months in storage. The oil also showed a broad fungitoxic spectrum, inhibiting the mycelial growth of other fungi, viz., Epidermophyton floccosum, M. nanum, T. rubrum, T. violaceum. Moreover, up to 5 % concentration it did not exhibit any adverse effect on mammalian skins. The oil has been formulated in the form of an ointment, 1 % w/v and subjected to topical testing on patients of the Out Patient Department (OPD) at Moti Lal Nehru Medical College, Allahabad. Patients were selected on the basis of KOHpositive results and diagnosed tenia corporis. After the second week of treatment, all patients were KOH- negative. At the end of medication, 75 % of patients recovered completely while 15 % showed significant improvement from the disease. The ointment thus, can be exploited commercially after ongoing successful clinical trials. Relationship of the dermatophytes to the toxicity of the oil vis-a-vis phylogeny using molecular data of the pathogens have also been discussed.