Biodiversity, current developments and potential biotechnological applications of phosphorus-solubilizing and -mobilizing microbes: A review

As one of the most important and essential macronutrients next to nitrogen, phosphorus (P) is important for plant development, but it is the least mobile nutrient element in plant and soil. Globally, P is mined from geological sediments and added to agricultural soils so as to meet the critical requirements of crop plants for agronomic productivity. Phosphorus exists in soil in both organic and inorganic forms. The various inorganic forms of the element in soil are salts with calcium, iron, and aluminum, whereas the organic forms come from decaying vegetation and microbial residue. There is a huge diversity of plant microbiomes (epiphytic, endophytic, and rhizospheric) and soil microbiomes that have the capability to solubilize the insoluble P and make it available to plant. The main mechanism for the solubilization of inorganic P is by the production of organic acids, which lowers soil pH, or by the production of acid and alkaline phosphatases, which causes the mineralization of organic P. The P-solubilizing and -mobilizing microorganisms belong to all three domains, comprising archaea, bacteria, and eukarya. The strains belonging to the genera Arthrobacter, Bacillus, Burkholderia, Natrinema, Pseudomonas, Rhizobium, and Serratia have been reported as efficient and potential P solubilizers. The use of P solubilizers, alone or in combination with other plant growth-promoting microbes as an eco-friendly microbial consortium, could increase the P uptake of crops, increasing their yields for agricultural and environmental sustainability.