Hunan Province Key Laboratory of Pollution Control and Resources Reuse Technology, University of South China, Hengyang 421001, China; Hunan Province Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, University of South China, Hengyang 421001, China.
School of Civil Engineering, University of South China, Hengyang 421001, China.
Sci Total Environ. 2022 Sep 20;840:156594. doi: 10.1016/j.scitotenv.2022.156594. Epub 2022 Jun 8.
The activated sludge represents a huge reservoir for antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Owing to the wastewater fluctuation, annual maintenance and storage requirement, the activated sludge in wastewater treatment plants (WWTPs) may suffer from substrate deficiency (i.e., starvation). Whereas the starvation has been confirmed to regulate the antibiotic resistance in numerous pure bacteria, its impacts on the antibiotic resistance in activated sludge remain unclear. Here, the dynamics of sulfonamide and tetracycline ARB and corresponding ARGs in three forms including intracellular ARGs (iARGs), adsorbed extracellular ARGs (aeARGs) and free extracellular ARGs (feARGs) in activated sludge upon exposure to starvation were investigated. The results showed that, among the different electron donors (i.e., carbon, nitrogen and phosphate), carbon starvation could effectively reduce the absolute abundance of ARB and aeARGs by up to 1.68 lgs and 2.62 lgs, respectively, and released a small amount of feARGs in wastewater with the maximum value of 1.1 × 10 copies/mL due to the high degree of sludge cell lysis and DNA adsorption/degradation. For the different acceptor conditions (that is, alternating anaerobic-aerobic, anaerobic, anoxic and aerobic), the anaerobic-aerobic starvation obviously mitigated the absolute abundance of ARB, aeARGs and iARGs by 0.71 lgs, 3.41 lgs and 1.35 lgs, respectively, via the substantial sludge cell lysis and DNA degradation. These findings demonstrated the response patterns and mechanisms of bacterial resistance in activated sludge to starvation stress, and thus provide clues to control the risk of antibiotic resistance in WWTPs by the starvation strategy.
活性污泥是抗生素耐药菌（ARB）和抗生素耐药基因（ARGs）的巨大储存库。由于废水波动、年度维护和储存要求，污水处理厂（WWTPs）中的活性污泥可能会遭受基质缺乏（即饥饿）。尽管饥饿已被证实会调节许多纯细菌中的抗生素耐药性，但它对活性污泥中抗生素耐药性的影响尚不清楚。在这里，研究了在经历饥饿时，活性污泥中磺胺类和四环素 ARB 及其相应的 ARGs 的三种形式（包括细胞内 ARGs（iARGs）、吸附的细胞外 ARGs（aeARGs）和游离的细胞外 ARGs（feARGs））的动态变化。结果表明，在不同的电子供体（即碳、氮和磷）中，碳饥饿可以有效地将 ARB 和 aeARGs 的绝对丰度分别降低 1.68 lgs 和 2.62 lgs，并且由于污泥细胞裂解和 DNA 吸附/降解程度高，会在废水中释放少量 feARGs，其最大值为 1.1×10 拷贝/mL。对于不同的接受条件（即交替缺氧-好氧、缺氧、缺氧和好氧），缺氧-好氧饥饿通过大量的污泥细胞裂解和 DNA 降解，明显将 ARB、aeARGs 和 iARGs 的绝对丰度分别降低了 0.71 lgs、3.41 lgs 和 1.35 lgs。这些发现表明了活性污泥中细菌对饥饿应激的抗性的响应模式和机制，从而为通过饥饿策略控制 WWTPs 中抗生素抗性的风险提供了线索。
