摘要
      活性污泥代表了抗生素抗性细菌（ARB）和抗生素抗性基因（ARGs）的巨大蓄水池。由于废水的波动、每年的维护和储存要求，污水处理厂中的活性污泥可能会出现底物缺乏（即饥饿）的问题。尽管饥饿已被证实可以调节许多纯细菌的抗生素耐药性，但其对活性污泥中抗生素耐药性的影响尚不清楚。本文研究了暴露于饥饿条件下，活性污泥中磺酰胺和四环素ARB以及三种形式的相应ARG的动力学，包括细胞内ARG（iARGs）、吸附的细胞外ARG（aeARGs）和游离的细胞外ARGs（feARG）。结果表明，在不同的电子供体（即碳、氮和磷酸盐）中，碳饥饿可以有效地使ARB和aeARGs的绝对丰度分别降低1.68 lgs和2.62 lgs，由于污泥细胞的高度裂解和DNA的吸附/降解，在废水中释放出少量的feARGs，最大值为1.1×105拷贝/mL。对于不同的受体条件（即交替的厌氧-好氧、厌氧、缺氧和好氧），厌氧-好气饥饿通过大量的污泥细胞裂解和DNA降解，使ARB、aeARGs和iARGs的绝对丰度分别明显降低了0.71 lgs、3.41 lgs和1.35 lgs。这些发现证明了活性污泥中细菌耐药性对饥饿应激的反应模式和机制，从而为通过饥饿策略控制污水处理厂中抗生素耐药性的风险提供了线索。
Abstract
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 × 105 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.

https://www.sciencedirect.com/science/article/abs/pii/S0048969722036919