Plant growth-promoting bacteria (PGPB) enhance plant growth by fixing nitrogen, solubilizing nutrients, and producing growth-promoting compounds. In environmental management, they can improve soil fertility, reduce the need for synthetic fertilizers, and mitigate soil erosion. In bioremediation, PGPB help detoxify heavy metal-polluted soil by immobilizing or degrading pollutants, making the soil safer for plant growth.

Dr B. Tabassum thank you for your contribution to the discussion

Plant growth promoting bacteria (PGPR) can increase grain yields, promote plant growth, reduce ethylene levels, increase nutrient availability, and improve soil structure and health. PGPB boost plant development and promote soil bioremediation by secreting a variety of metabolites and hormones, through nitrogen fixation, and by increasing other nutrients' bioavailability through mineral solubilization. Microorganisms have the potential to improve plant growth under abiotic stress conditions by promoting the production of low-molecular-weight osmolytes, such as glycinebetaine, proline, and other amino acids, mineral phosphate solubilization, nitrogen fixation, organic acids, and producing key enzymes. These microorganisms increase the nutrient bioavailability through nitrogen fixation and mobilization of key nutrients to the crop plants while remediate soil structure by improving its aggregation and stability. Plant growth-promoting rhizobacteria (PGPR) eliminate the effect of drought stress by altering root morphology, regulating the stress-responsive genes, producing phytohormones, osmolytes, siderophores, volatile organic compounds, and exopolysaccharides, and improving the 1-aminocyclopropane-1-carboxylate deaminase. Bioremediation is a process that can be applied to reduce the adverse effects of heavy metals in the soil. In this regard, bioremediation using plant growth–promoting rhizobacteria (PGPRs) as beneficial living agents can help to neutralize the negative interaction between the plant and the heavy metals. Bioremediation is the use of organisms for the treatment of polluted soils. It is a widely accepted method of soil remediation because it is perceived to occur via natural processes. Bacteria play a pivotal role in phytoremediation of metal-polluted soils. PGPB facilitate nutrient acquisition, supply phytohormones, and exert biocontrol. Different microbe-mediated processes remove and detoxify metals in soil. Microbes induce metal tolerance and the uptake or immobilization of metals in soil.

Growth-Promoting Bacteria and Environmental Management

Growth-promoting bacteria (GPB) are a diverse group of bacteria that can promote plant growth and development in a variety of ways. They can do this by:

• Fixing atmospheric nitrogen
• Solubilizing phosphorus and other nutrients
• Producing plant growth hormones
• Suppressing plant pathogens
• Increasing tolerance to abiotic stresses such as drought and salinity

GPB have a number of potential applications in environmental management, including:

• Bioremediation: GPB can be used to clean up contaminated soil and water by degrading pollutants such as heavy metals, pesticides, and petroleum hydrocarbons.
• Sustainable agriculture: GPB can be used to reduce the use of chemical fertilizers and pesticides, and to improve crop yields and resilience to pests and diseases.
• Forestry: GPB can be used to improve forest health and productivity, and to restore degraded forest ecosystems.
• Land reclamation: GPB can be used to reclaim degraded land, such as mine tailings and abandoned landfills.

Growth-Promoting Rhizobacteria (PGPR) in Bioremediation of Heavy Metal Polluted Soil

Plant growth-promoting rhizobacteria (PGPR) are a subset of GPB that colonize the roots of plants. PGPR are particularly effective at promoting plant growth in heavy metal polluted soils. They can do this by:

• Chelating heavy metals, making them less toxic to plants
• Increasing plant uptake of essential nutrients
• Stimulating plant growth and development
• Suppressing plant pathogens

PGPR have been used to successfully remediate heavy metal polluted soils in a variety of field trials. For example, one study found that the application of PGPR to soil contaminated with lead and cadmium resulted in a significant reduction in the levels of these metals in plant tissues. Another study found that PGPR could be used to improve the growth of trees in soil contaminated with copper and zinc.

The use of PGPR for the bioremediation of heavy metal polluted soils is a promising and sustainable approach. PGPR are relatively inexpensive and easy to apply, and they can be used to remediate a wide range of heavy metals.

Here are some specific examples of how PGPR have been used to remediate heavy metal polluted soil:

• Lead: PGPR have been shown to chelate lead ions, making them less available to plants. This can reduce the uptake of lead by plants and improve their growth.
• Cadmium: PGPR can also chelate cadmium ions and reduce their uptake by plants. In addition, PGPR can produce enzymes that help plants to detoxify cadmium.
• Copper: PGPR can help plants to tolerate high levels of copper in the soil. They can do this by increasing the production of antioxidants and by chelating copper ions.
• Zinc: PGPR can also help plants to tolerate high levels of zinc in the soil. They can do this by increasing the production of metallothioneins, which are proteins that bind to zinc ions.

Overall, PGPR have a significant role to play in the bioremediation of heavy metal polluted soil. They are a sustainable and effective approach to reducing the levels of heavy metals in plants and improving soil health.

Dr Murtadha Shukur thank you for your contribution to the discussion

Bioremediation is a process that can be applied to reduce the adverse effects of heavy metals in the soil. In this regard, bioremediation using plant growth–promoting rhizobacteria (PGPRs) as beneficial living agents can help to neutralize the negative interaction between the plant and the heavy metals. Bacteria play a pivotal role in phytoremediation of metal-polluted soils. PGPB facilitate nutrient acquisition, supply phytohormones, and exert biocontrol. Different microbe-mediated processes remove and detoxify metals in soil. Microbes induce metal tolerance and the uptake or immobilization of metals in soil. Properties and Potential of Plant Growth-Promoting Rhizobacteria (PGPR) Plant growth-promoting bacteria (PGPR) are soil bacteria living in the rhizosphere which, through the secretion of various regulatory molecules, are involved in promoting plant growth and development. PGPR has the ability to increase the availability of nutrient concentration in the rhizosphere by fixing nutrients, thus preventing them from leaching out. As an example, nitrogen, which is needed for the synthesis of amino acids and proteins, is the most limiting nutrient for plants. Microorganisms (bacteria, fungi, yeast or algae) sourced from their natural habitats can be excellent biosorbents. These biosorbents can absorb heavy metals at very low concentrations. The functional groups like amide, amine, carbonyl, carboxyl, etc. facilitate the removal of heavy metals. The plant growth-promoting rhizobacteria (or PGPR) are the beneficial microorganism that colonizes rhizosphere and help in promoting plant growth, protecting from biotic and abiotic stresses, and significantly increasing soil fertility. Rhizobacteria are stated as plant growth-promoting rhizobacteria (PGPR) because they inhabit the roots of the plant and help protect the plant from stresses, promoting plant growth, and substantially improving soil fertility.