Physiological and Molecular Responses of Anabaena laxa to Rac-Metalaxyl Fungicide: Exploring Metabolic and Oxidative Changes.

Rac-metalaxyl is a widely used fungicide for managing plant diseases; however, its environmental persistence and potential toxicity to aquatic microorganisms raise significant ecological concerns. Despite its widespread application, there is limited understanding of how cyanobacteria, which play vital ecological roles in aquatic systems, respond to such chemical stressors. This study addresses this gap by investigating the physiological and metabolic responses of the cyanobacterium Anabaena laxa to rac-metalaxyl exposure. Cultures were treated with 100 mg/L and 200 mg/L concentrations of the fungicide. Results showed increased intracellular accumulation of rac-metalaxyl at 200 mg/L, leading to significant reductions in cell growth, photosynthetic pigments, and the activities of key enzymes such as phosphoenolpyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase/oxygenase. Further elevated lipid peroxidation levels indicated oxidative damage. Consequently, rac-metalaxyl triggered substantial metabolic shifts, total soluble sugars increased by 7.66% at 100 mg/L and 67.48% at 200 mg/L; malic acid rose to 76.23% at 200 mg/L; amino acids increased by 27.14% at 100 mg/L and 48.8% at 200 mg/L; total fatty acids rose by 10.11% at 100 mg/L and 35.06% at 200 mg/L. These findings suggest that Anabaena laxa exhibits coordinated oxidative and metabolic responses to mitigate rac-metalaxyl toxicity, highlighting its potential resilience and role in the bioremediation of contaminated aquatic environments.