Microbial bioremediation offers a solution to the problem of residual antibiotics in wastewater associated with animal farms. Efficient degradation of antibiotic residues depends upon the genetic make-up of microbial degraders, which requires a comprehensive understanding of the degradation mechanisms. In this study, a novel, efficient tylosin (TYL)-degrading bacterium, Providencia stuartii TYL-Y13 (Y13) was isolated, which could completely degrade 100 mg/L TYL within 15 h under optimal operating conditions at 40 ℃, pH 7.0 %, and 1 % (v/v) bacterial inoculation rate. Whole genome sequencing revealed that strain Y13 consists of a circular chromosome and two plasmids. A new biodegradation pathway of TYL including desugarification, hydrolysis, and reduction reactions was proposed through the analysis of biodegradation products. It was demonstrated that strain Y13 gradually decreased the biotoxicity of TYL and its metabolites based on the results of the ecological structural activity relationships (ECOSAR) model analysis and toxicity assessment. Moreover, Y13 promoted the reduction of the target macrolide resistance genes in wastewater and disappeared within 84 h. These results shed new light on the mechanism of TYL biodegradation and better utilization of microbes to remediate TYL contamination.

微生物生物修复为解决与动物养殖场相关的废水中残留抗生素的问题提供了解决方案。抗生素残留物的有效降解取决于微生物降解剂的基因组成，这需要全面了解降解机制。在这项研究中，一种新型的高效泰乐菌素 (TYL) 降解菌普罗维登西亚分离得到TYL-Y13 (Y13)，在40 ℃、pH 7.0 %、细菌接种率1 % (v/v)的最佳操作条件下，可在15 h内完全降解100 mg/L TYL。全基因组测序显示 Y13 菌株由一个环状染色体和两个质粒组成。通过对生物降解产物的分析，提出了一种新的TYL生物降解途径，包括脱糖、水解和还原反应。基于生态结构活性关系（ECOSAR）模型分析和毒性评估结果表明，菌株Y13逐渐降低了TYL及其代谢物的生物毒性。此外，Y13促进了废水中目标大环内酯类抗性基因的减少，并在84小时内消失。