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.