玉米秸秆低温降解复合菌系降解能力及微生物组成研究

根据还田秸秆配施尿素的生产实际,对玉米秸秆低温高效降解复合菌系GF-20进行氮源培养基驯化,探明其菌种组成和功能多样性及其与菌源菌种结构差异,完善复合菌系筛选方法,促进其开发利用。本文以低温高效降解复合菌系GF-20为研究对象,在硫酸铵和尿素不同配比下连续继代培养10代,获得不同氮源菌系(硫酸铵处理N1,硫酸铵和尿素混合处理N2-N5,尿素处理N6),测定其玉米秸秆降解率,评价复合菌系秸秆降解效率;采用MiSeq高通量测序对菌源土壤样品及不同氮源下继代培养的复合菌系菌种组成和功能多样性进行研究。结果显示N2处理玉米秸秆降解率显著高于其他处理;菌源土壤的Alpha多样性指数显著高于继代培养后的复合菌系,不同处理间N2处理显著高于其他氮处理;菌源和复合菌间以及不同氮处理间菌种组成具有显著差异, N2处理菌种组成多样性较高,菌群结构更加丰富、均匀,且碳水化合物的代谢通路丰度较高。菌源经限制性继代筛选后得到了参与玉米秸秆降解过程的功能菌,能有效提高秸秆降解率,其在硫酸铵和尿素氮源为0.16%+0.04%的条件下,菌系的秸秆降解效率较高,这为复合菌的生产实际开发利用提供了理论依据。

Straw degradation ability and composition of microbial consortium for corn straw decomposition at low temperature

It is common practice to return field straw with urea to accelerate decomposition. To improve the microbial screening methodology and investigate the microbes responsible for decomposition of corn straw, nitrogen acclimatization of the microbial consortium GF-20 (GF-20) was performed. Compositional differences in the cultured microbial consortium and the microbe source were also evaluated. GF-20 was cultured until the 10^th generation in variable nitrogen conditionsammonium sulfate (N1), mixtures of ammonium sulfate and urea (N2-N5), and urea (N6)]. The corn straw decomposition ratio was determined to estimate the activity of the composite microbial system, and the composition diversity and function were analyzed by MiSeq high-throughput sequencing. The results showed that the N2 degradation rate was significantly higher than the other treatments. The bacterial source alpha diversity index (ADI) was significantly higher than the cultured microbial consortium, and the N2 ADI was significantly higher than the other nitrogen treatments. The bacterial composition also significantly differed between the source and consortium, as well as among the nitrogen treatments. The N2 treatment yielded the most diverse bacterial composition, with richer and more uniform flora structures and a higher carbohydrate metabolic pathway activity (which promotes corn straw degradation). Functional microbial strains involved in corn straw degradation were obtained after restrictive sub-generation of the microbial sources, which can accelerate corn straw degradation. The highest corn straw degradation efficiency of microbial consortium was observed with the 0.16% ammonium sulfate + 0.04% of urea nitrogen (N2) treatment. These findings provide a basis for developing microbial consortium used in commercial production decomposition.