四环素对污泥蚯蚓粪中微生物种群和抗性基因的影响

Effects of Tetracycline on Microbial Communities and Antibiotic Resistance Genes of Vermicompost from Dewatered Sludge

城市污泥中高含量的四环素可能会致使污泥蚯蚓堆肥产物中携带高丰度的抗性基因,降低其利用价值.本实验采用赤子爱胜蚓处理添加不同含量四环素(100、500和1 000 mg·kg-1)的新鲜污泥,以不添加为对照组,分析微生物种群和四环素抗性基因(tet C、tet G、tet M、tet W和tet X)及整合子基因(int I1)在不同四环素选择性压力下的变化,揭示四环素含量对污泥蚯蚓堆肥中微生物种群和抗性基因的影响.结果表明,添加四环素降低了污泥蚯蚓堆肥产物中变形菌门的丰度但增加了拟杆菌门的丰度,且四环素的含量与细菌的Shannon和Pielou指数有明显的负相关关系.同时,添加四环素致使int I1增加了4.25倍;四环素类抗性基因增加了4.7~186.9倍,其中tet M基因丰度与四环素含量呈现出显著的正相关关系.因此初始污泥中较高含量的四环素会改变污泥蚯蚓粪的微生物种群结构,增加抗生素抗性基因的丰度和传播风险.

The high content of tetracycline in municipal sludge may result in vermicomposting products carrying a high abundance of antibiotic resistance genes,thus lowering the utilization value of the vermicompost. Hence,this study aimed to reveal the underlying effects of tetracycline concentrations on the resistance genes involved in vermicomposting systems for sludge recycling. For this purpose,fresh sludge substrates with different concentrations of tetracycline( 100,500,and 1000 mg·kg-1) were vermicomposted for60 days using Eisenia foetida. In parallel,sludge treatment without the addition of the tetracycline was used as a control. During the experiment,changes in bacterial communities,tetracycline resistance genes( tet C,tet G,tet M,tet W,and tet X),and class 1 integron( int I1) were detected using high-throughput sequencing and qualitative PCR,respectively. The results showed that the addition of tetracycline reduced the abundance of Proteobacteria but increased the abundance of Bacteroidetes in the sludge vermicompost.Furthermore,the concentrations of tetracycline had a significant negative correlation with Shannon and Pielou indexes of bacterial diversity. In addition,tetracycline increased int I1 genes and tetracycline resistance genes in the sludge by 4. 25 times and 4. 7-186. 9 times,respectively. Moreover,there was a significantly positive correlation between the abundance of tet M genes and tetracycline concentration. This study suggests that higher concentration of tetracycline in sludge can modify the microbial community structure of vermicompost,enhancing the abundance of antibiotic resistance genes and their associated dissemination risks.