Does algal trophic mode affect the removal of norfloxacin? Insights from Tetradesmus obliquus

The potential influence of algal trophic modes on antibiotic removal and the underlying mechanisms remain poorly understood. In this study, we selected the typical microalga Tetradesmus obliquus to analyze norfloxacin (NFX) removal efficiency and elucidate the intrinsic mechanisms driving this process in aquatic environment. This was achieved through a systematic evaluation of key physiological parameters, biochemical components, and transcriptome sequencing under photoautotrophic, heterotrophic, and mixotrophic modes. The results demonstrated that T. obliquus achieved the highest NFX removal efficiency under the mixotrophic mode (62.67 %), and the lowest under the photoautotrophic mode (7.41 %). This enhancement was attributed to increased biomass production, elevated total extracellular polymeric substances (EPS) content, and a strengthened antioxidant capacity. Furthermore, differential gene expression analysis revealed that the synergy of central carbon metabolism and xenobiotic metabolism drives efficient norfloxacin removal in mixotrophic T. obliquus . In summary, these findings offer novel perspectives on how different trophic modes impact the removal of NFX by microalgae, and elucidate the underlying mechanisms, thereby establishing a theoretical framework for enhancing microalgal treatment technologies of antibiotic-containing wastewater.