纳米二氧化钛驱动的人工湿地基质微生物群落差异

Variation of microbial community in constructed wetland substrate motivated by nano titanium dioxide

纳米二氧化钛颗粒(TiO2-NPs)已越来越多出现在污水处理系统中。为探究TiO2-NPs对以火山石为基质的人工湿地(CW)系统中微生物群落的影响,利用16S rDNA高通量测序技术,分析不同TiO2-NPs浓度(0、60、110和160 mg·L^-1)短期(18 d)暴露后的微生物群落差异。结果显示,短期暴露下,CW中γ-变形菌纲(Gammaproteobacteria)和类杆菌纲(Bacteroidia)的相对丰度受影响不显著(P>0.05),但α-变形菌纲(Alphaproteobacteria)和硝化螺旋菌纲(Nitrospira)等优势菌种对TiO2-NPs较敏感而相对丰度显著降低(P<0.05)。3种浓度处理的TiO2-NPs对CW中微生物产生不同程度的生态毒性,60 mg·L^-1的TiO2-NPs在暴露18 d后对Nitrospira抑制程度最大,110和160 mg·L^-1浓度下Nitrospira相对丰度略有回升。Alpha多样性指数表明,110 mg·L^-1时菌群多样性最低,此浓度对菌群抑制最大;Beta多样性也证实此浓度处理中菌群多样性与对照差异最大,其次是60 mg·L^-1。T-test进一步表明,110 mg·L^-1TiO2-NPs处理中的5个纲,例如δ-变形菌纲(Deltaproteobacteria)和Nitrospira等是变化显著的类群(P<0.05);13个科,例如黄杆菌科(Flavobacteriaceae)、硝化螺菌科(Nitrospiraceae)和不明α-变形菌科(unidentifiedAlphaproteobacteria)是变化显著的科(P<0.05)。表明TiO2-NPs可能会严重降低CW系统的硝化效率。3个浓度的TiO2-NPs均影响CW基质中细菌群落组成和多样性,且对各物种的影响存在差异,将影响CW中污染物降解和转化。研究结果为揭示纳米材料对微生物的潜在危害和CW技术的应用提供参考。

TiO2 nanoparticles(TiO2-NPs)have emerged frequently in wastewater treatment systems.To explore the effects of TiO2-NPs on the microbial communities in the constructed wetland(CW)system filled by volcanic rock,16S rDNA high-throughput sequencing technology was used to analyze the differences in microbial communities among treatments of different TiO2-NPs concentrations(0,60,110,160 mg·L^-1)after short-term exposure(18 d).The results showed that the relative abundances of Gammaproteobacteria and Bacteroidia in CW were not affected(P>0.05),while the dominant species such as Alphaproteobacteria and Nitrospira were more sensitive to TiO2-NPs,with their relative abundances being significantly reduced(P<0.05).Three concentrations of TiO2-NPs had distinct ecotoxicities to the microbes in CW.The inhibition of 60 mg·L^-1 TiO2-NPs on Nitrospira was the greatest after 18 days exposure.The relative abundance of Nitrospira increased slightly at the TiO2-NPs concentrations of 110 and 160 mg·L^-1.The lowest microbial community diversity was presented at the treatment of 110 mg·L^-1 TiO2-NPs,indicating the highest inhibition of microbes at this level.Further,such level led to the highest difference in microbial community diversity compared with the control treatment,followed by the TiO2-NPs concentration of 60 mg·L^-1.In the 110 mg·L^-1 TiO2-NPs treatment,five microbial classes showed significant variations(P<0.05),including Deltaproteobacteria and Nitrospira;and 13 families showed significant changes(P<0.05),such as Flavobacteriaceae,Nitrospiraceae and unidentified Alphaproteobacteria.Our results suggested that TiO2-NPs might seriously reduce the nitrification efficiency of CW system.The three concentrations of TiO2-NPs all affected the composition and diversity of bacterial community in CW,but with different effects on various taxa,which would affect the degradation and transformation of pollutants in CW.Our results provide a reference for understanding the potential harm of nanomaterials to microorganisms and the application of CW technology.