Role of Plant Growth Promoting Rhizobacteria in the Remediation of Metal Contaminated Soils: A Review. In: Lichtfouse E, editor. Organic Farming, Pest Control and Remediation of Soil Pollutants. Dordrecht: Springer Netherlands; 2010. pp. 319-50. [DOI: 10.1007/978-1-4020-9654-9_15]

Study on Adsorption of Cd in Solution and Soil by Modified Biochar-Calcium Alginate Hydrogel

Contamination with cadmium (Cd) is a prominent issue in agricultural non-point source pollution in China. With the deposition and activation of numerous Cd metal elements in farmland, the problem of excessive pollution of agricultural produce can no longer be disregarded. Considering the issue of Cd pollution in farmland, this study proposes the utilization of cross-linked modified biochar (prepared from pine wood) and calcium alginate hydrogels to fabricate a composite material which is called MB-CA for short. The aim is to investigate the adsorption and passivation mechanism of soil Cd by this innovative composite. The MB-CA exhibits a higher heavy metal adsorption capacity compared to traditional biochar and hydrogel due to its increased oxygen-containing functional groups and heavy metal adsorption sites. In the Cd solution adsorption experiment, the highest Cd2+ removal rate reached 85.48%. In addition, it was found that the material also has an excellent pH improvement effect. Through the adsorption kinetics experiment and the soil culture experiments, it was determined that MB-CA adheres to the quasi-second-order kinetic model and is capable of adsorbing 35.94% of Cd2+ in soil. This study validates the efficacy of MB-CA in the adsorption and passivation of Cd in soil, offering a novel approach for managing Cd-contaminated cultivated land.

Roles of Phosphate Solubilizing Microorganisms from Managing Soil Phosphorus Deficiency to Mediating Biogeochemical P Cycle

Phosphorus (P) is a vital element in biological molecules, and one of the main limiting elements for biomass production as plant-available P represents only a small fraction of total soil P. Increasing global food demand and modern agricultural consumption of P fertilizers could lead to excessive inputs of inorganic P in intensively managed croplands, consequently rising P losses and ongoing eutrophication of surface waters. Despite phosphate solubilizing microorganisms (PSMs) are widely accepted as eco-friendly P fertilizers for increasing agricultural productivity, a comprehensive and deeper understanding of the role of PSMs in P geochemical processes for managing P deficiency has received inadequate attention. In this review, we summarize the basic P forms and their geochemical and biological cycles in soil systems, how PSMs mediate soil P biogeochemical cycles, and the metabolic and enzymatic mechanisms behind these processes. We also highlight the important roles of PSMs in the biogeochemical P cycle and provide perspectives on several environmental issues to prioritize in future PSM applications.

Understanding the molecular mechanisms for the enhanced phytoremediation of heavy metals through plant growth promoting rhizobacteria: A review

Rapid industrialization, modern agricultural practices and other anthropogenic activities add a significant quantity of toxic heavy metals into the environment, which induces severe toxic effects on all form of living organisms, alter the soil properties and its biological activity. Remediation of heavy metal contaminated sites has become an urgent necessity. Among the existing strategies, phytoremediation is an eco-friendly and much convincing tool for the remediation of heavy metals. However, the applicability of phytoremediation in contaminated sites is restricted by two prime factors such as i) slow growth rate at higher metal contaminated sites and ii) metal bioavailability. This circumstance could be minimized and accelerate the phytoremediation efficiency by incorporating the potential plant growth promoting rhizobacterial (PGPR) as a combined approach. PGPR inoculation might improve the plant growth through the production of plant growth promoting substances and improve the heavy metal remediation efficiency by the secretion of chelating agents, acidification and redox changes. Moreover, rhizobacterial inoculation consolidates the metal tolerance and uptake by regulating the expression of various metal transporters, tolerant and metal chelator genes. However, the exact underlying molecular mechanism of PGPR mediated plant growth promotion and phytoremediation of heavy metals is poorly understood. Thus, the present review provides clear information about the molecular mechanisms excreted by PGPR strains in plant growth promotion and phytoremediation of heavy metals.