From soil to survival: PGPB-triggered defense and adaptation in plants

Plants and beneficial soil bacteria engage in dynamic and reciprocal interactions that influence plant development, nutrient acquisition, and stress resilience. Among these, plant growth- promoting bacteria (PGPB) have garnered considerable attention due to their ability to support plant health through a range of biochemical and physiological mechanisms. These bacteria produce a variety of bioactive compounds that enhance plant stress tolerance, improve nutrient availability, and offer protection against phytopathogens. PGPB influence plant performance through both direct and indirect mechanisms. Direct pathways include the biosynthesis of phytohormones (such as indole-3-acetic acid), solubilization of essential nutrients like phosphate, zinc, and potassium, ammonia production, and atmospheric nitrogen fixation.
Indirectly, they contribute by secreting siderophores, lytic enzymes, hydrogen cyanide, and antibiotics, which suppress harmful microorganisms and enhance plant immunity. These functional traits position PGPB as valuable components in sustainable agriculture, especially for the development of bioformulants including biofertilizers, biopesticides, and biofungicides.
Such alternatives reduce dependency on chemical inputs and contribute to environmentally responsible crop management. Nonetheless, despite the expanding repertoire of beneficial strains, the practical implementation of PGPB in agriculture remains challenging. Factors such as microbial survival, strain specificity, plant-microbiome compatibility, and fluctuating environmental conditions can influence their efficacy in field applications. This review explores recent advances in understanding PGPB-mediated plant adaptations to abiotic and biotic stressors, with emphasis on molecular mechanisms, signaling pathways, and metabolite production. It also discusses formulation strategies and delivery systems designed to maximize their stability and performance. Ultimately, leveraging PGPB potential requires a deeper integration of microbiology, plant physiology, and environmental science to ensure their consistent and scalable use in sustainable agricultural systems.