Performances of Microbial Community and Antibiotic Resistance Genes during Enrichment of Tetracycline-Degrading Bacteria: Inspired from Metagenomic Analysis

Degradation of tetracycline by pure strain and mixed bacteria has been widely reported. However, the enrichment mechanism of tetracycline-degrading bacteria has not been analyzed through biological information. In this study, the changes of the microbial community and antibiotic resistance genes were revealed based on the metagenomic technology when the tetracycline-degrading bacteria were enriched. The results showed that the most dominant phylum in final enriched sludge was Proteobacteria (37.0%), followed by Chloroflexi (17.6%), Bacteroidetes (8.4%), and Nitrospirae (4.1%). The biochemical properties and functional microbial changes of sludge under tetracycline selective pressure were analyzed. The abundance of tetracycline resistance genes (i.e., tetP/B and tetT) was significantly reduced during the whole enrichment process. Furthermore, the main microorganisms in the enrichment process of tetracycline-degrading bacteria were detected at the genus level. Additionally, characteristics of carbohydrate-active enzymes were analyzed, suggesting that their relative abundances were generally decreasing, except for GT83, GH74, GH13, PL22, AA3, and GH23. The enrichment mechanism of tetracycline-degrading bacteria was explained. These findings further deepen our understanding of the biodegradation mechanism of tetracycline.