Plant growth promoting Rhizobacteria and their biofilms in promoting sustainable agriculture and soil health

Plant growth promoting rhizobacteria (PGPR) are the most important class of rhizobacteria that offer a wide range of benefits to plants by influencing the plant growth through diverse mechanisms including solubilization of phosphate, production of siderophores, biological nitrogen fixation, phytohormone production, demonstrating antifungal activity, induction of systemic resistance, promoting beneficial plant-microbe symbioses, interference with pathogen toxin production, and many more. The PGPR bacterial strains are also responsible in conferring resistance against phytopathogens as well as in mitigating stresses. The PGPR associate with plants and aggregates to form biofilm at nutrient and moist-rich sites. Rhizobacterial biofilms increase the possibilities for sustainable agricultural production, being involved in plant growth and promotion, nutrient and water uptake, and plant stress tolerance. The PGPR biofilms further facilitate the maintenance of soil quality and health by nutrient cycling, carbon transformation, and maintaining soil structure and pest control. This chapter emphasis on rhizobacteria and its biofilms as a potent natural fertilizer and elucidating their mechanisms of action for inducing plant growth and crop yield.