Mitigation of cadmium-induced oxidative stress in maize (Zea mays L.) by Anoxybacillus caldiproteolyticus through antioxidant defense modulation

Abstract

Cadmium (Cd) is a toxic heavy metal that severely restricts plant growth by inducing oxidative stress and metabolic imbalance. This study evaluated the potential of Anoxybacillus caldiproteolyticus to mitigate Cd-induced stress in maize (Zea mays L.) under controlled conditions. Plants were exposed to 100 & micro;M Cd with or without bacterial inoculation (102 CFU mL-1). Cd treatment markedly reduced germination (95.3% to 44.1%), root length (16.24 to 7.06 cm), shoot length (8.69 to 4.23 cm), and dry weight (0.0645 to 0.0543 g), while increasing oxidative damage. Bacterial inoculation partially alleviated these effects, improving germination to 49.6% and increasing root and shoot lengths to 11.0 and 5.37 cm, respectively. Under Cd stress, inoculation significantly enhanced antioxidant enzyme activities, with superoxide dismutase, catalase, and glutathione reductase increasing by 117%, 140%, and 13%, respectively, compared to Cd-treated plants. In contrast, peroxidase activity decreased by 48.57%, likely reflecting reduced hydrogen peroxide levels. These changes were accompanied by reduced reactive oxygen species accumulation and lipid peroxidation. Importantly, Cd accumulation in plant tissues was not significantly altered, indicating that stress mitigation was associated with improved physiological tolerance rather than reduced metal uptake. Overall, A. caldiproteolyticus enhances maize resilience through antioxidant modulation and maintenance redox balance.