Microbial Interactions and Bacterial Responses to Metal Stress in Plants: Mechanisms, Adaptations, and Applications for Sustainable Agriculture

Metal stress in plants poses a significant challenge to global agriculture, reducing crop productivity and threatening food security. While recent advancements in microbiology and bacteriology have revealed the potential of plant-associated microbes to alleviate heavy metal toxicity, practical applications remain constrained by knowledge gaps and environmental variability. This review critically examines the dynamic interactions between plants and microbes under metal stress, focusing on specific microbial communities and their multifaceted roles in reducing metal toxicity. Key bacterial mechanisms, including biofilm formation, metal sequestration, antioxidant production, and stress-related gene expression, are explored for their contributions to plant resilience. Additionally, we discuss the diverse strategies employed by bacteria, such as the production of siderophores, phytohormones, and extracellular polymeric substances (EPS), to enhance metal tolerance in plants. Special emphasis is placed on the contributions of rhizobacteria, endophytes, and other plant-growth-promoting bacteria (PGPB) in bioremediation and sustainable agriculture. The review also highlights challenges, such as the variability of microbial efficacy in different environmental contexts, and emphasizes the need for field-scale studies to validate laboratory findings. By integrating microbial insights with plant physiological responses, this review provides a critical framework for harnessing microbial interventions to combat metal stress and achieve sustainable agricultural practices in metal-contaminated environments.