氯和紫外消毒过程中胞外抗性基因的产生特征

考察了城市污水氯和紫外消毒过程中不同物理形态的胞外抗性基因的产生行为与及微生物群落的关联特征.结果表明，氯消毒尽管使胞内抗性基因丰度下降，但使结合型胞外抗性基因丰度明显上升（0.7±0.1）log，而游离型胞外抗性基因丰度下降（0.2±0.1）log.紫外消毒也使胞内抗性基因下降，但使游离型胞外抗性基因显著上升（0.4±0.2）log，而结合型胞外抗性基因丰度下降（0.3±0.1）log.氯消毒后，结合型胞外DNA（a-eDNA）中变形菌门丰度下降而其他菌门的丰度上升，细菌多样性指数由4.2上升到4.7；而游离型胞外DNA（f-eDNA）中变形菌门上升了6.6%，多样性指数则从3.5降低到2.8.紫外消毒后，a-eDNA中变形菌门丰度下降了36.6%，多样性则上升到4.8，而f-eDNA中细菌丰度变化较小.分子生态网络分析揭示了抗性基因与细菌间广泛的寄存关系，tetA、tetX、sulI和sulII分别与17、15、15和5种菌属间存在共现性，表明抗性基因潜在宿主的变化是导致消毒后胞外抗性基因产生的关键原因.本研究表明氯和紫外消毒不能消除抗性基因风险，反而通过导致不同胞外抗性基因的大量产生，使风险的形式发生变化.

Generation of extracellular antibiotic resistance genes during municipal wastewater chlorination and UV disinfection

In this study, the generation of eARGs in different physical forms during wastewater chlorination and ultraviolet (UV) disinfection was investigated, and the correlation with microbial communities was explored. Results indicated that though chlorination decreased the abundance of intracellular ARGs, absorbed eARGs was significantly amplified by (0.7±0.1)log, while the abundance of free eARGs decreased by (0.2±0.1)log. UV disinfection also decreased the abundance of intracellular ARGs, but caused a significant increase of free eARGs ((0.4±0.2)log) and a decrease of absorbed eARGs ((0.3±0.1)log). Post chlorination, the abundance of most phyla increased while Proteobacteria decreased in the absorbed extracellular DNA (a-eDNA), resulting in a increase of the bacterial diversity index from 4.2 to 4.7. Whereas, Proteobacteria increased by 6.6% in the free extracellular DNA (f-eDNA) after chlorination, causing a decrease of the bacterial diversity index from 3.5 to 2.8. Post UV disinfection, the abundance of Proteobacteria in a-eDNA decreased by 36.6%, while the bacterial diversity index increased to 4.8; the abundance of bacteria in f-eDNA changed slightly. The molecular ecological network analysis indicated a wide hosting relationship between ARGs and bacteria genera. tetA, tetX, sulI and sulII were correlated with 17, 15, 15 and 5genera respectively, suggesting changes in potential hosts post disinfection were essential mechanisms of the eARGs generation. This study shows that chlorination and UV disinfection can't eliminate the risk of antibiotic resistance but only change patterns of the risk by inducing the generation of adsorbed and free eARGs.