Arsenic Removing Soil Indigenous Bacteria of Hyper Arsenic Contaminated Region in Bihar

Unboxing PGPR-mediated management of abiotic stress and environmental cleanup: what lies inside?

Abiotic stresses including heavy metal toxicity, drought, salt and temperature extremes disrupt the plant growth and development and lowers crop output. Presence of environmental pollutants further causes plants suffering and restrict their ability to thrive. Overuse of chemical fertilizers to reduce the negative impact of these stresses is deteriorating the environment and induces various secondary stresses to plants. Therefore, an environmentally friendly strategy like utilizing plant growth-promoting rhizobacteria (PGPR) is a promising way to lessen the negative effects of stressors and to boost plant growth in stressful conditions. These are naturally occurring inhabitants of various environments, an essential component of the natural ecosystem and have remarkable abilities to promote plant growth. Furthermore, multifarious role of PGPR has recently been widely exploited to restore natural soil against a range of contaminants and to mitigate abiotic stress. For instance, PGPR may mitigate metal phytotoxicity by boosting metal translocation inside the plant and changing the metal bioavailability in the soil. PGPR have been also reported to mitigate other abiotic stress and to degrade environmental contaminants remarkably. Nevertheless, despite the substantial quantity of information that has been produced in the meantime, there has not been much advancement in either the knowledge of the processes behind the alleged positive benefits or in effective yield improvements by PGPR inoculation. This review focuses on addressing the progress accomplished in understanding various mechanisms behind the protective benefits of PGPR against a variety of abiotic stressors and in environmental cleanups and identifying the cause of the restricted applicability in real-world.

Efficiency of arsenic remediation from growth medium through Bacillus licheniformis modulated by phosphate (PO4)3- and nitrate (NO3)- enrichment

Bacillus licheniformis DAS-1 and DAS-2 were found as potent tool for removal/uptake of arsenic [As(V) and As(III)] and reduction [(As(V) to As(III)] of arsenic from the liquid growth medium in our previous studies. Present work gives light on modulation of arsenic remediation (in terms of uptake and reduction) by two selected essential soil nutrients, phosphate (PO₄)^3- and nitrate (NO₃)^-. PO₄^3- has structural analogy with arsenate [AsO₄^3-/As(V)] that compete with cell uptake of As(V). It was found that enrichment of 0.75 mM of PO₄^3- had significantly moderated the As(V) toxicity in liquid broth culture by retarding As(V) uptake. Lowering level of PO₄^3- can lead to increase in As(V) removal from medium and vice versa. NO₃^- has strong oxidant properties which controls As(III) oxidation into As(V) in medium that resulted less toxicity favouring growth of bacteria and also more uptake via phosphate transporters. Hence, accelerated As(III) uptake has shown on enrichment of 0.5 mM of NO₃^- in medium. All the results of work give evidence that appropriate enrichment of PO₄^3- and NO₃^- into liquid growth medium, can significantly contribute in alteration of efficiency for arsenic removal/uptake and reduction by bacteria from the medium.

Unlocking the potential of plant growth-promoting rhizobacteria on soil health and the sustainability of agricultural systems

The concept of soil health refers to specific soil properties and the ability to support and sustain crop growth and productivity, while maintaining long-term environmental quality. The key components of healthy soil are high populations of organisms that promote plant growth, such as the plant growth promoting rhizobacteria (PGPR). PGPR plays multiple beneficial and ecological roles in the rhizosphere soil. Among the roles of PGPR in agroecosystems are the nutrient cycling and uptake, inhibition of potential phytopathogens growth, stimulation of plant innate immunity, and direct enhancement of plant growth by producing phytohormones or other metabolites. Other important roles of PGPR are their environmental cleanup capacities (soil bioremediation). In this work, we review recent literature concerning the diverse mechanisms of PGPR in maintaining healthy conditions of agricultural soils, thus reducing (or eliminating) the toxic agrochemicals dependence. In conclusion, this review provides comprehensive knowledge on the current PGPR basic mechanisms and applications as biocontrol agents, plant growth stimulators and soil rhizoremediators, with the final goal of having more agroecological practices for sustainable agriculture.