Paenibacillus polymyxa: A Prominent Biofertilizer and Biocontrol Agent for Sustainable Agriculture

Agricultural practice is currently moving from traditional chemical fertilizers and pesticides toward sustainable and environment-friendly biofertilizer and biocontrol agents. Paenibacillus polymyxa (previously Bacillus polymyxa) is an agriculturally important microbe widely studied for its plant growth-promoting abilities. P. polymyxa is an endospore-forming bacterium that could colonize a range of ecological niches. It is commonly found in the agricultural soils, especially in close association with plants, and has been isolated from diverse geographic locations. P. polymyxa is renowned for its ability to act as a biocontrol agent against a wide array of plant pathogens. It can produce antibiotic compounds like polymyxin and antifungal compounds like fusaricidin that can suppress the growth of pathogens in both lab and field conditions. Apart from being a potent biocontrol agent, P. polymyxa strains are also known widely for their ability to fix atmospheric nitrogen, solubilize phosphate, and produce phytohormones; thus they could be used as effectual biofertilizers in commercial agriculture. The aim of this chapter is to provide an overview about both direct and indirect plant growth promotion accomplished by P. polymyxa in a wide variety of agricultural crops, through extensive reviewing of old and recent studies.