Changes of antibiotic resistance genes and bacterial communities in the advanced biological wastewater treatment system under low selective pressure of tetracycline. (1st December 2021)

• Record Type: Journal Article
• Authors: Zhang, Yongpeng; Pei, Mengke; Zhang, Bo; He, Yiliang; Zhong, Yanxia
• Is Part Of: Water research. Volume 207(2021)
• Publication Date: 2021-12-01
• Subjects: Advanced biological wastewater treatment system -- Selective pressure -- ARGs -- Bacterial diversity -- Plants -- Vertical transfer; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2021.117834
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: ABWWTS was efficient at removing tetracycline and ARGs. Levels of ARGs were lower in ABWWTS than in UBWWTS after tetracycline exposure. Bacterial diversity increased within UBWWTS and ABWWTS under tetracycline exposure. Tetracycline resistance genes increased within systems under tetracycline exposure. Sub-MIC tetracycline exposure facilitated the vertical transfer of ARGs in E. coli . Abstract: Effluents of conventional wastewater treatment systems contain antibiotic residues at concentrations below the minimal inhibitory concentrations (MIC), which nevertheless could still select for antibiotic-resistant bacteria. This work focuses on evaluating the changes of antibiotic resistance genes (ARGs) and bacterial communities in a planted advanced biological wastewater treatment system (ABWWTS) under long-term exposure to sub-MIC tetracycline. In the ABWWTS, the removal rates of tetracycline ranged from 97.9% to 99.9%, and a 17.2% decrease in the average removal rates of NH4 + -N was observed after the addition of tetracycline. Although the background of ABWWTS contributed to the ARGs in effluents, the concentration of 283 targeted ARGs (ΣARGs) was 83.5% lower in effluents than in influents after sub-MIC tetracycline exposure, and the concentrations of ΣARGs in the ABWWTS were, on average, 30.0% lower than those in an unplanted biological wastewater treatment system (UBWWTS) after a performance of 130 days. The relative abundance of tetracycline resistance genes increased within ABWWTS and UBWWTS under tetracycline exposure. After tetracycline exposure, bacterial diversity in ABWWTS and UBWWTS increased on average by 36.2% and 42.7%, respectively, and the abundances of Nitrosomonas and Nitrospira in the aerobic zone were more than 10-times higher in the ABWWTS than in the UBWWTS. Sub-MIC tetracycline concentrations were linearly correlated with the relative abundance of tetracycline resistance genes in Escherichia coli ( E. coli ). Long-term exposure to tetracycline at the same concentration increased abundances of the same ARGs (i.e., tetR-02 and tetM-01 ) in E. coli and the microflora of the ABWWTS, revealing that sub-MIC tetracycline could increase the abundance of ARGs in the ABWWTS by facilitating the vertical transfer of tetracycline resistance genes. These findings demonstrated that planted ABWWTS played a positive role in removing ARGs under low antibiotic selective pressure, which was in accompany with increasing levels of corresponding ARGs within the system. Graphical abstract: Image, graphical abstract