外源Zn对土壤抗生素抗性基因及细菌群落的诱导作用

Induction of Antibiotic Resistance Genes and Bacterial Community in Soil by Exogenous Zn

采用高通量测序和实时定量PCR技术,基于室内培养法研究不同Zn浓度对土壤氨基糖苷类抗生素抗性基因(antibiotic resistance genes,ARGs)、可移动遗传元件(mobile genetic elements,MGEs)及细菌群落的影响。结果表明,Zn的浓度和处理时间对氨基糖苷类ARGs及MGEs影响不同。1000 mg·kg^(-1)Zn处理60 d时,acc、aacC1和整合子int11的相对丰度最高,分别为对照的4.1、9.7和3.7倍;800 mg·kg^(-1)Zn处理60 d时,aac(6′)-II的相对丰度最大,为对照的13.7倍。Zn处理显著提高了转座子Tp614的相对丰度,100 mg·kg^(-1)Zn处理时最高,为对照的4.6倍。Zn处理降低了细菌群落的多样性指数,提高了优势度指数,说明Zn的毒性使敏感菌群消失,抗性菌群增加。冗余分析表明Zn胁迫的时长对细菌群落结构的影响大于浓度;胁迫时长相同时,较低浓度的Zn(100~400 mg·kg^(-1))与较高浓度的Zn(800~1000 mg·kg^(-1))处理的土壤细菌群落的结构差异明显;Zn胁迫与Nocardioides、Adhaeribacter及Arthrobacter等的丰度负相关,而与Flavisolibacter、Sphingomonas及Solirubrobacter的丰度正相关。网络共存分析显示,Zn胁迫压力下,acc、aac(6′)-II、aacC1和int11、IS613连接数较高;Steroidobacter与Tp614存在连接,可能是Tp614的潜在宿主菌。研究表明,高浓度Zn污染能加速土壤ARGs传播扩散,即使低浓度的Zn长时间作用也能诱导部分ARGs和MGEs,提高水平转移的风险,值得重点关注。

Using high throughput sequencing and real-time PCR techniques,the effects of added Zn on relative abundance of aminoglycoside antibiotic resistance genes(ARGs),mobile genetic elements(MGEs)and bacterial communities in soil were studied by indoor culture.The results show that Zn concentration and treatment time had different effects on aminoglycoside ARGs and MGEs.After treatment with 1000 mg·kg^(-1) Zn for 60 d,the relative abundances of acc,aacC1 and integron int11 were the highest,which were 4.1,9.7 and 3.7 times as those of the control,respectively.When 800 mg·kg^(-1) Zn was treated for 60 d,the relative abundance of aac(6′)-Ⅱwas the highest,which was 13.7 times as that of the control.The relative abundance of transposon Tp614 was significantly increased only after 60 d of Zn treatment,and the highest relative abundance was obtained at 100 mg·kg^(-1) Zn treatment,which was 4.6 times that of the control.Zn stress decreased the diversity index of bacterial community and increased the dominance index,indicating that Zn toxicity caused the disappearance of sensitive bacteria and the increase of resistant bacteria.Redundancy analysis show that the effect of Zn stress duration on bacterial community structure was greater than that of Zn concentration.When the treatment time was equal,the structure of soil bacterial community was significantly different between low concentration Zn(100-400 mg·kg^(-1))and high concentration Zn(800-1000 mg·kg^(-1)).Zn treatment was negatively correlated with Nocardioides,Adhaeribacter and Arthrobacter,and positively correlated with Flavisolibacter,Sphingomonas and Solirubrobacter.The network coexistence analysis show that acc,aac(6′)-Ⅱ,aacC1 and int11,IS613 had high connections under Zn stress;Steroidobacter was connected to Tp614,which may be the potential host of Tp614.The studies have shown that high concentration of Zn pollution can accelerate the spreading and diffusion of soil ARGs.Even if low concentration of Zn exists for a long time,some ARGs and MGEs can be induced,and the risk of horizontal transfer can also be increased,which is worthy of attention.