Abiotic Factors as Functional Drivers of Plant Growth-Promoting Rhizobacteria: Interconnections in Agricultural Systems

Climate change is increasingly impacting agricultural production systems, driving the intensified use of chemical inputs to ensure sustained productivity. This trend has progressively led to environmental deterioration and adverse effects on the health of agricultural workers. At the same time, various abiotic factors, intensified by climate change, play a central role in shaping the structure and functional activity of plant growth-promoting rhizobacteria (PGPR). Environmental stressors such as nutrient limitations, drought, salinity, flooding, pH fluctuations, and heavy metal contamination exert drastic changes on soil structure, imposing strong selective pressures on rhizobacterial populations and influencing their composition, metabolic activity, and plant interaction. These stress factors not only affect the survival and diversity of PGPR but also modulate key functional traits associated with plant growth and productivity, including nutrient solubilization, phytohormone production, and mechanisms involved in both abiotic and biotic stress alleviation. This review analyzes the influence of multiple abiotic factors on the functional modulation and ecological performance of beneficial rhizobacteria. In the rhizosphere, where plant roots actively interact with soil bacteria, abiotic stress conditions can disrupt microbial balance and plant–microbe signaling, ultimately affecting plant health and productivity. However, certain PGPR taxa (e.g., Pseudomonas spp., Bacillus spp.) exhibit adaptive responses that enable them to thrive under adverse conditions, thereby contributing to plant resilience. Importantly, these environmental factors rarely occur in isolation; rather, their interactions can generate complex and context-dependent effects on soil properties, plant physiology, and rhizobacterial functions, ultimately shaping multi-factor interactions that drive agricultural sustainability. Understanding how abiotic factors interact with one another and shape the functional dynamics of plant growth-promoting rhizobacteria is essential for developing sustainable agricultural strategies, particularly in the face of increasing environmental variability.