Mitigating Lead and Chromium Toxicity in Agriculture: The Role of Bacillus tequilensis RCDB-1 as a Dual Bioremediation and Biofertilizer Agent

Abstract

This study investigates the heavy metal tolerance and plant growth-promoting (PGP) potential of the bacterial strain of Bacterial strain CDB-1 (PP762244) under Lead (Pb) and Chromium (Cr) stress. The growth kinetics of CDB-1 were evaluated across varying metal concentrations, pH levels, and temperatures to determine its physiological limits. Results demonstrated that Bacterial strain CDB-1 possesses robust tolerance to increasing concentrations of Pb and Cr, maintaining high metal-removal efficiency. In vivo experiments using tomato (Solanum lycopersicum) plants revealed that bacterial inoculation significantly alleviated metal-induced phytotoxicity, promoting enhanced shoot height, root elongation, and nodulation compared to non-inoculated metal-treated controls. Furthermore, Physiological analysis demonstrated a distinct dose-dependent enzymatic response to metal stress; as Pb and Cr concentrations increased to 350 mg/L, superoxide dismutase (SOD) activity was significantly upregulated by 47.5% to counteract oxidative damage. Conversely, dehydrogenase (DHA) activity exhibited a 49.1% inhibition, indicating a metabolic trade-off between antioxidant defense and energy production. Greenhouse experiments further confirmed that the inoculation of CDB-1 enhanced the growth parameters of S. lycopersicum, including plant height and root length, under heavy metal stress compared to non-inoculated controls. To the best of our knowledge, this study provides critical insights into the dual role of Bacterial strain CDB-1 as both a growth promoter and a biosorbent. This study suggests the potential of using EPS-producing microbes as a sustainable biotechnological tool to improve crop productivity and detoxify heavy metal-polluted agricultural ecosystems.