PGP Bacteria as Key Drivers for Cadmium Mitigation in Agricultural Ecosystems

Cadmium (Cd) contamination in agricultural ecosystems poses a critical challenge due to its toxicity, impact on human health, and threats to environmental sustainability (Massa et al., Microorganisms 2022). As a highly mobile and bioavailable metal, Cd readily migrates from soil and water into the edible portions of crops. Current management strategies to mitigate Cd levels focus on reducing its bioavailability in soil and minimizing its transfer to plant tissues. Among these, the use of Cd-tolerant plant growth-promoting (PGP) bacteria has emerged as a promising solution offering a sustainable strategy for mitigating Cd contamination in agricultural systems (Xiao et al., Ecotoxicology and Environmental Safety, 2023). The aim of this study is to characterize Cd resistant bacterial strains with PGP activity towards edible plants in the presence of the metal in order to assess the possibility to use bioinoculants to reduce Cd uptake. Within the screened collection, Serratia plymuthica strains As3-5a(5) (Cd MIC > 3 mM) and SC3-I2 (Cd MIC > 4 mM), and Pseudomonas koreensis strain 69RS (Cd MIC > 2 mM) exhibited PGP activities also in the presence of Cd. Particularly, their ACC deaminase activity was higher in the presence of 0.4 mM Cd(II). In plant growth pouches experiments, root and shoot biomass and seed germination of Oryza sativa (L.) and Solanum Lycopersicon (L.) increased in inoculated plants in the presence of 0.1 and 0.5 mM Cd(II). The present work highlighted the ability of Cd-resistant PGP bacteria to increase Cd resistance of plants and ongoing experiments will ascertain their effect on metal uptake in plant tissues. Acknowledgments: This work was supported by PSR 2021 Linea 6 1H_HUB project. A.M. is awarded by a PhD fellowship by the University of Milan - Food Systems PhD Program.