State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing210023, China.
School of Environmental Science and Engineering, Nanjing Tech University, Nanjing211816, China.
Environ Sci Technol. 2022 Dec 6;56(23):17166-17176. doi: 10.1021/acs.est.2c06158. Epub 2022 Oct 26.
To advance the understanding of antibiotic resistance propagation from wastewater treatment plants, it is important to elucidate how different effluent disinfection processes affect the dissemination of predominantly extracellular antibiotic resistance genes (eARGs). Here, we show that, by facilitating proximal adsorption to recipient cells, bacterial debris generated by chlorination (but not by UV irradiation) increases the natural transformation frequency of their adsorbed eARG by 2.9 to 7.2-fold relative to free eARGs. This is because chlorination increases the bacterial surface roughness by 1.1 to 6.7-fold and the affinity toward eARGs by 1.6 to 5.8-fold, and 98% of the total eARGs released after chlorination were adsorbed to cell debris. In contrast, UV irradiation released predominantly free eARGs with 18% to 56% lower transformation frequency. The collision theory indicates that the ARG donor-recipient collision frequency increased by 35.1-fold for eARGs adsorbed onto chlorination-generated bacterial debris, and the xDLVO model infers a 29% lower donor-recipient contact energy barrier for these ARGs. Exposure to chlorination-generated bacterial debris also upregulated genes associated with natural transformation in (e.g., encoding the major activator of natural transformation) by 2.6 to 5.2-fold, likely due to the generation of chlorinated molecules (5.1-fold higher Cl content after chlorination) and persistent reactive species (e.g., carbon-centered radicals) on bacterial debris. Increased proximal eARG adsorption to bacterial debris was also observed in the secondary effluent after chlorination; this decreased eARG decay by 64% and increased the relative abundance of ARGs by 7.2-fold. Overall, this study highlights that different disinfection approaches can result in different physical states of eARGs that affect their resulting dissemination potential via transformation.
为了深入了解抗生素耐药性从污水处理厂的传播，阐明不同的出水消毒工艺如何影响主要为细胞外抗生素耐药基因（eARGs）的传播非常重要。在这里，我们表明，通过促进与受体细胞的近程吸附，氯化（而不是紫外线照射）产生的细菌碎片将其吸附的 eARG 的自然转化频率提高了 2.9 至 7.2 倍，与游离的 eARGs 相比。这是因为氯化作用使细菌表面粗糙度增加了 1.1 至 6.7 倍，对 eARGs 的亲和力增加了 1.6 至 5.8 倍，并且氯化作用后释放的 98%总 eARGs 被吸附到细胞碎片上。相比之下，紫外线照射释放的主要是游离的 eARGs，其转化频率降低了 18%至 56%。碰撞理论表明，对于吸附在氯化细菌碎片上的 eARGs，ARG 供体-受体碰撞频率增加了 35.1 倍，而 xDLVO 模型推断这些 ARGs 的供体-受体接触能垒降低了 29%。暴露于氯化细菌碎片还使与自然转化相关的基因（例如，编码自然转化主要激活子的基因）上调了 2.6 至 5.2 倍，这可能是由于氯化分子（氯化后 Cl 含量增加了 5.1 倍）和持久的反应性物质（例如，碳中心自由基）在细菌碎片上的产生。在氯化后的二级出水中也观察到 eARG 更靠近细菌碎片的吸附增加；这使 eARG 的衰减减少了 64%，并使 ARGs 的相对丰度增加了 7.2 倍。总体而言，本研究强调了不同的消毒方法可能导致不同的 eARG 物理状态，从而通过转化影响其传播潜力。
