Gibberellic acid enhances cadmium tolerance and metabolic resilience in Chlorella sp.: Physiological and untargeted metabolomic evidence.
Abstract
Heavy metal pollution poses a major threat to aquatic ecosystems, and characterizing algal physiological and metabolic responses to cadmium Cd(Ⅱ) can inform the development of bioremediation strategies. This study investigated the effects of exogenous gibberellic acid (GA3) on Cd(Ⅱ)-induced stress in Chlorella sp. Cd(Ⅱ) exposure (4 mg/L) significantly reduced algal growth, photosynthetic efficiency, and chlorophyll synthesis, while increasing oxidative damage. Supplementation with GA3 (5-30 mg/L) partially alleviated these effects, improving biomass and Fv/Fm values and enhancing Cd(Ⅱ) increasing Cd(Ⅱ) removal efficiency to 86 % under the tested culture conditions, likely reflecting combined contributions from rapid biosorption and subsequent metabolism-associated processes. Microscopy and three‑dimensional excitation-emission matrix fluorescence indicated increased extracellular polymeric substance production and improved cell surface integrity in GA3 treated cultures. GA3-treated cells also exhibited higher superoxide dismutase and catalase activities and lower malondialdehyde levels, consistent with enhanced antioxidant capacity. Untargeted metabolomics indicated that Cd(Ⅱ) exposure was associated with broad disturbances in amino acid, lipid, and carbon metabolism, whereas GA3 co treatment was associated with higher abundances of intermediates linked to the Calvin cycle, pentose phosphate pathway, and nucleotide metabolism, consistent with a partial recovery of central carbon flux and redox capacity. Overall, these results indicate that exogenous GA3 alleviates Cd(Ⅱ) associated physiological impairments in Chlorella sp., and metabolomic profiles suggest multi pathway metabolic adjustments consistent with improved redox balance, supporting the potential of hormone assisted algal Cd(Ⅱ) removal.
Abstract as supplied by the indexing source. © the authors / publisher.