Effects of successional sulfadiazine exposure on biofilm in moving bed biofilm reactor: Secretion of extracellular polymeric substances, community activity and functional gene expression.

[Display omitted] • SDZ reduced the PN and PS contents of EPS by 28.7%-55.1% and 33.3%-61.4%. • Deterministic assembly process of biofilm transcriptome was evident in SDZ exposure. • SDZ stimulated the upregulation of FPKM levels of transporter protein genes. • The EPS, ARGs and transporter protein genes had direct effects on SDZ removal. The effects of sulfadiazine (SDZ) on responses of biofilm in a moving bed biofilm reactor were explored with emphasis on the changes in extracellular polymeric substances (EPS) and functional genes. It was found that 3 to 10 mg/L SDZ reduced the protein (PN) and polysaccharide (PS) contents of EPS by 28.7%-55.1% and 33.3%-61.4%, respectively. The EPS maintained high ratio of PN to PS (10.3–15.1), and the major functional groups within EPS remained unaffected to SDZ. Bioinformatics analysis showed that SDZ significantly altered the community activity such as increased expression of s_ Alcaligenes faecali. Totally, the biofilm held high SDZ removal rates, which were ascribed to the self-protection by secreted EPS, and genes levels upregulation of antibiotic resistance and transporter protein. Collectively, this study provides more details on the biofilm community exposure to an antibiotic and highlights the role of EPS and functional genes in antibiotic removal. [ABSTRACT FROM AUTHOR]