芘对土壤微生物氮转化功能菌群的影响特征

Characterization of pyrene's impact on the soil functional microorganisms for nitrogen transformation

通过构建好氧降解微环境,分析环境浓度下的芘(12.09mg/kg)对土壤酶活性,氮转化全过程以及相关功能微生物的影响.结果发现,芘仅在降解第1d显著促进了脲酶活性,而在降解最初和后期均显著刺激了脱氢酶活性.从细菌群落结构分析可知,由于氨氧化菌(Nitrososphaeraceae)相对丰度的变化,导致花在处理前期对其介导的好氧氨氧化,硝化功能表现为促进作用,在后期表现为抑制作用,而对于固氮细菌(Bradyrhizobium,Mesorhizobium和Ensifer),尿素分解细菌(Roseomonas)以及硝酸盐还原细菌(Opitutus)则作用相反.与微生物群落结构以及相关功能预测的变化不同,功能基因定量分析表明,芘虽在培养初期对固氮基因nifH表现为抑制作用,但nifH的丰度呈增长趋势.结合土壤氨氧化和反硝化过程中关键酶活性及编码基因的变化,芘在培养前期未促进氨氧化过程,但在15d后明显抑制了土壤氨氧化和反硝化过程,其中对氨氧化过程的抑制作用更为显著.本研究阐明了芘对土壤微生物氮转化过程的影响特征,为了解芘的环境风险提供重要参考价值.

An aerobic degradation microenvironment was constructed to analyze the effects of pyrene(12.09mg/kg)at ambient concentration on soil enzyme activities,the whole process of nitrogen transformation and related functional microorganisms.The results showed that pyrene only significantly increased urease activity on the first day of degradation,but promoted the dehydrogenase activity at both the early and late phases of degradation.The analysis of the bacterial community structure revealed that the variation of the relative abundance of ammonia-oxidizing bacteria(Nitrososphaeraceae)promoted pyrene-mediated aerobic ammonia oxidation and nitrification in the early stages of treatment and inhibited that in the late stages.In contrast,the effects of nitrogen-fixing bacteria(Bradyrhizobium,Mesorhizobium and Ensifer),urea-degrading bacteria(Roseomonas),and nitrate-reducing bacteria(Opitutus)were opposite.The quantitative analysis of functional genes showed that,despite pyrene's repressive effect on the nitrogen-fixing gene nifH at the start of the culture,the abundance of nifH showed an increasing trend,which was not consistent to the anticipated changes in microbial community structure and associated functions.Compared with changes in key enzyme activities and genes encoding the processes of ammonia oxidation and denitrification,pyrene did not significantly boost ammonia oxidation in the early stages of incubation,t severely hampered ammonia oxidation and denitrification after 15days,significantly inhibited the ammonia oxidation process.In this study,how pyrene influenced the microbial nitrogen transformation process in soil was reported,fundamental data on understanding the environmental hazard of pyrene were provided.