Decrypting the multi-functional biological activators and inducers of defense responses against biotic stresses in plants

Plant diseases are still the main problem for the reduction in crop yield and a threat to global food security. Additionally, excessive usage of chemical inputs such as pesticides and fungicides to control plant diseases have created another serious problem for human and environmental health. In view of this, the application of plant growth-promoting rhizobacteria (PGPR) for controlling plant disease incidences has been identified as an eco-friendly approach for coping with the food security issue. In this review, we have identified different ways by which PGPRs are capable of reducing phytopathogenic infestations and enhancing crop yield. PGPR suppresses plant diseases, both directly and indirectly, mediated by microbial metabolites and signaling components. Microbial synthesized anti-pathogenic metabolites such as siderophores, antibiotics, lytic enzymes, hydrogen cyanide, and several others act directly on phytopathogens. The indirect mechanisms of reducing plant disease infestation are caused by the stimulation of plant immune responses known as initiation of systemic resistance (ISR) which is mediated by triggering plant immune responses elicited through pathogen-associated molecular patterns (PAMPs). The ISR triggered in the infected region of the plant leads to the development of systemic acquired resistance (SAR) throughout the plant making the plant resistant to a wide range of pathogens. A number of PGPRs including Pseudomonas and Bacillus genera have proven their ability to stimulate ISR. However, there are still some challenges in the large-scale application and acceptance of PGPR for pest and disease management. Further, we discuss the newly formulated PGPR inoculants possessing both plant growth-promoting activities and plant disease suppression ability for a holistic approach to sustaining plant health and enhancing crop productivity

Plant-Microbe Interaction in Improving Zinc Nutrition in Rice: A Review

Zinc is an essential micro-nutrient that affects metabolic activities, including growth and cell proliferation in all living organisms. Zinc deficiency in agricultural soil has been increasing at an accelerated rate all over the world, leading to its deficiency in plants as well as humans. Zinc solubilising bacteria (ZSB) solubilise complex zinc in soil into plant absorbable compounds through several mechanisms such as the production of acid, chelating compounds, protons etc. further improving its bioavailability in plants and humans. Improving zinc nutrition through microbes is an effective measure to overcome its deficiency. ZSB with Plant Growth Promoting (PGP) traits can be an additional advantage as along with increasing zinc amount in plant it would also promote overall growth of plants through PGP traits and can act as a biocontrol agent against several crop pathogens. In this review we attempt to study the significance of zinc; status and deficiency of zinc in Indian soil and to understand how zinc solubilizing bacteria can prove to be an effective measure to increase zinc content in plants and overcome its deficiency

Potential of novel bacterial consortium for the remediation of chromium contamination

This study was aimed to examine the efficiency of a novel bacterial consortium on the reduction of toxic hexavalent chromium [Cr(VI)] to non-toxic trivalent Cr [Cr(III)]. Six Cr(VI)-resistant bacteria (IS1-IS6) were isolated from a tannery waste disposal site at Mount Barker, South Australia, of which three viz., IS1, IS2 and IS3 were selected based on Cr(VI) reduction ability in minimal salt medium. The isolates were identified as Bacillus endophyticus (IS1), Microbacterium paraoxydans (IS2) and Bacillus simplex (IS3) by 16S rRNA gene sequencing. All three isolates were able to tolerate chromium (Cr(VI), 300–400 mg L−1), arsenic (As(V), 1,000 mg L−1), copper (Cu(II), 300–400 mg L−1) and lead (Pb(II), 1,000 mg L−1). The isolates were evaluated both as an individual and as a consortia for Cr(VI) reduction in minimal salt medium and storm water, both spiked with 100 mg Cr(VI) L−1. In both cases, the rate of Cr(VI) reduction was found to be significantly higher in the bacterial consortium inoculation (t ½ = 8.45 for minimal salt medium; 6.02 h for storm water), compared to inoculation with individual isolates (t ½ = 53.3–115.5 h for minimal salt medium; 8.77–9.76 h for storm water). The rate of Cr(VI) reduction in both minimal salt medium and storm water was found to be higher in bacterial consortium inoculation (IS1 + IS2 + IS3) than in individual isolate inoculation. This experiment demonstrated that bacterial consortium prepared by using B. endophyticus, M. paraoxydans and B. simplex was more effective in Cr(VI) detoxification than application of individual bacterium. This experiment also proved that a bacterial consortium was more effective in Cr(VI) detoxification than the application of individual bacterial strain

Emerging frontiers in microbial-mediated utilization of crop residues for economically valuable biomaterials

Agricultural crop residues include leftover and unmarketable materials, such as crop stover, weeds, leaf litter, sawdust, forest litter, and livestock manure originating from crop cultivation, and post-harvest activities. Such residues are a storehouse of plant nutrients and several other resources and therefore need to be managed in an environment- friendly manner with minimum loss of plant nutrients and other resources that can be recovered. Microbial starter consortia are a key component in the rapid recycling of farm residue wastes and the production of other valuable products, such as biogas, bioethanol/biofuel, enzymes, molecules, and metabolites. Recent advances in microbial biotechnology can also facilitate the conversion of farm residues into economically valuable materials, i.e. soil additives, adsorbents, energy, and enzymes, thereby contributing to a circular economy. This special issue attempts to compile the latest advancements in the field of agricultural crop residue management for enhanced nutrient recycling and resource recovery by the use of compost starters and inoculant formulations

Evaluation of serum magnesium levels among type 2 diabetes individuals of a South Indian town

Background: Studies have reported that hypomagnesemia could play an essential role in the development of endothelial dysfunction and altered insulin function, particularly among type 2 diabetes mellitus (T2DM). To assess the incidence of hypomagnesemia among patients with T2DM and compare them with healthy individuals. Materials and Methods: One hundred types 2 diabetic patients admitted to the general medicine outpatient Department at Government Erode Medical College Hospital, Perundurai, were recruited. Biochemical parameters and serum magnesium were assessed at admission and compared with the 100 healthy controls without T2DM. Results: Cases and controls had mean ages of 50.39 ± 9.76 and 50.01 ± 10.15 years, respectively. The age range of 41–50 had the highest percentage of patients (42%). The gender distribution was the same for both cases and controls, with 70% of men and 30% of women. Between cases and controls, the mean fasting blood sugar levels were 102.42 ± 11.16 mg/dl and 91.93 ± 4.32 mg/dl, respectively. Conclusion: Hypomagnesemia is a common problem in adults with T2DM, and we did find a significant association between Mg levels and T2DM in Erode district, Tamil Nadu

Enzymes-mediated solid waste management: A sustainable practice for recycling

Different anthropogenic activities, extensive applications of agrochemicals, and industrialization have significantly altered natural environmental processes through the generation of solid waste. Based on the sources of origin and chemical behavior, the impact of solid waste on the environment varies. Currently, it is essential to tackle novel methods to reduce the impact of solid waste on the environment. Approaches such as open burning, landfills, incineration, composting, and pyrolysis are effective against solid waste; however, the introduction of sustainable and efficient approaches is essential to overcome the problems of conventional practices. Enzyme-mediated solid waste management is an extensively applicable strategy owing to its specificity for catalytic reactions. Enzyme-mediated remediation directly or indirectly degrades pollutants by modifying the chemical and physical properties of waste. Hydrolases, lipases, oxidoreductases, oxygenases, and laccases are the major enzymes involved in the conversion of hazardous wastes into non-toxic or biodegradable materials. To boost the activity of enzymes or for profitable industrialization, it is mandatory to incorporate modern strategies, such as omics analysis, genetic engineering, and nanotechnology, that aid in the development of new tolerant enzyme mutants with high efficiency. This review comprehensively covers the recent trends in enzyme-mediated biotransformation of toxic waste materials to non-toxic materials for a stable, sustainable, and healthy environment

The Foliar Application of Rice Phyllosphere Bacteria induces Drought-Stress Tolerance in <i>Oryza sativa</i> (L.)

This study assessed the potential of Bacillus endophyticus PB3, Bacillus altitudinis PB46, and Bacillus megaterium PB50 to induce drought tolerance in a susceptible rice cultivar. The leaves of the potted rice plants subjected to physical drought stress for 10 days during the flowering stage were inoculated with single-strain suspensions. Control pots of irrigated and drought-stressed plants were included in the experiment for comparison. In all treatments, the plant stress-related physiochemical and biochemical changes were examined and the expression of six stress-responsive genes in rice leaves was evaluated. The colonization potential on the surface of the rice leaves and stomata of the most successful strain in terms of induced tolerance was confirmed in the gnotobiotic experiment. The plants sprayed with B. megaterium PB50 showed an elevated stress tolerance based on their higher relative water content and increased contents of total sugars, proteins, proline, phenolics, potassium, calcium, abscisic acid, and indole acetic acid, as well as a high expression of stress-related genes (LEA, RAB16B, HSP70, SNAC1, and bZIP23). Moreover, this strain improved yield parameters compared to other treatments and also confirmed its leaf surface colonization. Overall, this study indicates that the foliar application of B. megaterium PB50 can induce tolerance to drought stress in rice

Potential inhibitors of SARS-CoV-2 (COVID 19) proteases PLpro and Mpro/ 3CLpro: molecular docking and simulation studies of three pertinent medicinal plant natural components

The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) - coronavirus disease 2019 (COVID-19) has raised a severe global public health issue and creates a pandemic situation. The present work aims to study the molecular -docking and dynamic of three pertinent medicinal plants i.e. Eurycoma harmandiana, Sophora flavescens and Andrographis paniculata phyto-compounds against SARS-COV-2 papain-like protease (PLpro) and main protease (Mpro)/3-chymotrypsin-like protease (3CLpro). The interaction of protein targets and ligands was performed through AutoDock-Vina visualized using PyMOL and BIOVIA-Discovery Studio 2020. Molecular docking with canthin-6-one 9-O-beta-glucopyranoside showed highest binding affinity and less binding energy with both PLpro and Mpro/3CLpro proteases and was subjected to molecular dynamic (MD) simulations for a period of 100ns. Stability of the protein-ligand complexes was evaluated by different analyses. The binding free energy calculated using MM-PBSA and the results showed that the molecule must have stable interactions with the protein binding site. ADMET analysis of the compounds suggested that it is having drug-like properties like high gastrointestinal (GI) absorption, no blood-brain barrier permeability and high lipophilicity. The outcome revealed that canthin-6-one 9-O-beta-glucopyranoside can be used as a potential natural drug against COVID-19 protease