Acclimation-enhanced ofloxacin biodegradation by Tetradesmus obliquus: Unveiling physiological and transcriptomic adaptation mechanisms

The widespread use of antibiotics, particularly ofloxacin (OFL), has led to their persistent presence in aquatic environments. The acclimation of Tetradesmus obliquus ( T. obliquus ) using OFL was found to enhance both its tolerance and degradation capability. After 14 d of exposure to 1 mg/L OFL, the degradation rate of the acclimated T. obliquus was 25.81% higher than the non-acclimated, mainly due to enhanced bioaccumulation and biodegradation. Physiological and biochemical analyses showed that acclimated T. obliquus experienced significantly less growth inhibition and oxidative stress under OFL exposure than non-acclimated. Transcriptome results show that OFL exposure impacts DNA replication and repair, photosynthesis, membranes, oxidoreductases, and energy metabolism in both non-acclimated and acclimated T. obliquus . Acclimated T. obliquus by adjusting carbon metabolism to boost energy, enhancing antioxidant enzymes, upregulating ABC transporters to expel antibiotics, increasing carotenoid synthesis for photosynthetic protection, and using amino acid synthesis to offset reduced protein production. These adaptations greatly improve the survival and degradation abilities of algae that were acclimated through repeated OFL exposure. Molecular docking and dynamics simulations suggested the possible formation of new complexes between SOD and GST during acclimation. Overall, this study provides valuable insights into the adaptation of algae to antibiotic pollution and highlights the potential of acclimated microalgae for advanced bioremediation strategies.