Role of plant growth promoting bacteria in alleviating heavy metals induced oxidative stress in plant systems: a review

Soil contamination with heavy metals has emerged as a significant concern in the modern world. Exposure to these metals induces various toxic effects on biotic communities within ecosystems, notably oxidative stress. To counteract metal-induced oxidative stress, biotic communities have evolved complex antioxidant defense mechanisms. Over the past two decades, numerous studies have underscored the pivotal role of rhizosphere microorganisms—particularly plant growth-promoting bacteria (PGPB)—in mitigating metal-induced oxidative stress in plants. For example, Pseudomonas sp. CPSB21 was shown to reduce Cr(VI)-induced oxidative stress in Solanum lycopersicum L. and Helianthus annuus by enhancing the activity of catalase (24.0–33.8%), peroxidase (8.7–15.6%), and superoxide dismutase (5.8–13.8%), while simultaneously lowering malondialdehyde levels by 27.8 to 33.6%. This review explores the role of PGPB in modulating both enzymatic and non-enzymatic antioxidant systems to alleviate metal-induced oxidative stress in plants. Drawing on current findings, it emphasizes the importance of evaluating individual PGPB strains across diverse plant species, metal contaminants, soil types, and environmental conditions. Furthermore, it highlights the need for precise quantification of antioxidant activity at the molecular level. This perspective addresses a critical research gap in understanding the functional capacity of PGPB in mitigating oxidative stress, aiming to enhance their application in environmental and agricultural sustainability.