Mechanistic insights into the impact of Lincomycin on microalgal-bacterial granular sludge in domestic wastewater treatment

Lincomycin (LCM), a widely used lincosamide antibiotic, poses considerable ecological risks, particularly when residues remain in wastewater. Microalgal-bacterial granular sludge (MBGS) has emerged as a sustainable and efficient technology for domestic wastewater treatment. Nonetheless, the effects of residual LCM on MBGS performance remains largely unexplored. This study examined the impact of varying LCM concentrations on MBGS under simulated domestic wastewater treatment conditions. Our results indicated that 10 mg/L LCM concentrations stimulated MBGS to secrete extracellular polymeric substances (EPS), thereby enhancing both adsorption and biodegradation of LCM. Nevertheless, LCM exposure impaired MBGS efficiency, notably in water treatment and nitrogen cycling processes. Amplicon sequencing revealed that the deterioration of wastewater-treatment efficiency was associated with a reduced abundance of cyanobacteria and bdelloidea. Moreover, metagenomic analysis corroborated that LCM exposure diminished cyanobacteria abundance and highlighted the pivotal role of cyanobacteria in both nitrogen assimilation and dissimilation. LCM exposure impaired nitrogen cycling efficiency, disrupting the production of cofactors production and vitamin metabolism. Furthermore, LCM induced an increase in antibiotic resistance genes (ARGs), which may support MBGS survival under antibiotic stress. This study provides a comprehensive elucidation of the multifaceted impact mechanisms of LCM on MBGS. Additionally, it highlights the critical role of cyanobacteria in nitrogen cycling and their susceptibility to LCM exposure, thereby offering insights into the ecological ramifications of antibiotic pollution in wastewater treatment systems. Overall, this study provides critical insights for the development of more efficient and sustainable MBGS-based wastewater-treatment systems.