Algae-driven bacterial production of extracellular reactive oxygen species for emerging contaminants degradation

Emerging contaminants (ECs) are ubiquitous in natural surface waters, posing significant risks to aquatic ecosystems and human health. Symbiotic systems comprising photoautotrophic algae and associated bacteria offer a promising approach for the bioremediation of aquatic environments. This study investigated the degradation of five ECs (carbamazepine, diclofenac, atenolol, sulfamethoxazole, and ofloxacin) by reactive oxygen species (ROS) generated through algal-bacterial interactions. The algal-bacterial system exhibited superior degradation efficiencies, achieving 96 %, 97 %, 89 %, 72 %, and 77 % removal for the respective ECs after 6 days, far surpassing the performance of pure bacterial or algal systems. Elevated levels of biogenic ROS were observed in the algal-bacterial system, with extracellular superoxide radicals (O₂^•-) and hydrogen peroxide (H₂O₂) identified as key drivers of the degradation process. Under ECs stress, the algal-bacterial system maintained cellular integrity and metabolic activity by upregulating pathways related to carbohydrate, lipid, amino acid, and nucleotide metabolism, thereby enhancing its resistance. These findings highlight the significant potential of algal-bacterial systems for the transformation of ECs, offering a sustainable strategy for bioremediation and the restoration of ecosystem health.