Synergistic effect of copper ions on Pseudomonas sp. DX-21 for enhanced tetracycline removal: A mechanistic study

The widespread occurrence of tetracycline (TC) in wastewater poses a significant threat to ecological balance. Thus far, the ability of the strains screened to degrade TC has been relatively limited. How to enhance the metabolic capacity of existing strains to efficiently remove TC remains an urgent issue to be addressed. Here, Cu²⁺ was added to improve the metabolism of strain DX-21. The TC removal rate increased from 0.309 mg/(L·h) in the control to 0.343 mg/(L·h) at a Cu²⁺ concentration of 0.5 mg/L. Cu²⁺ increased extracellular polymeric substance (EPS) secretion and improved intracellular and extracellular enzyme activities. The degradation rate of TC increased when TC-Cu complexes were present. Moreover, Cu²⁺ led to a decrease of two with respect to the types of byproducts produced during DX-21 degradation, the reaction process was more efficient, and there was no significant change in the biological effects of the degradation products. Moreover, the ability of the Cu²⁺ and TC-Cu complexes to increase the removal of TC by DX-21 was verified via transcriptome analysis and molecular docking simulations. Therefore, this study deepens the understanding of the role played by metal ions in the microbial removal of TC and reveals the potential of bioaugmentation to enhance antibiotic removal in wastewater through the addition of metal ions.