降解水稻秸秆的复合菌系及其微生物群落结构演替

Characterization and microbial community shifts of rice strawdegrading microbial consortia

摘要:

[目的] 比较和分析从堆肥中富集的水稻秸秆降解菌系F1和F2的纤维素分解能力、微生物群落结构及其在秸秆降解过程中的演替，从而探究微生物群落结构与秸秆降解效率的相关性。[方法] 采用DNS （3，5-二硝基水杨酸，3，5-dinitrosalicylic acid）定糖法测定发酵液中的外切纤维素酶活；采用范氏（Van Soest）洗涤纤维分析法测定发酵前与发酵后的秸秆纤维素、半纤维素、木质素的含量，并计算降解率；采用16S rRNA基因序列分析和实时荧光定量PCR （Quantitative real-time PCR，Q-PCR）对秸秆降解过程中的微生物物种组成及特定的功能微生物进行定性和定量分析。[结果] 复合菌系F1的水稻秸秆总降解率、纤维素降解率、半纤维素降解率显著高于复合菌系F2；2种复合菌系的外切纤维素酶活性与cel48基因的拷贝数变化趋势一致；复合菌系F1的物种较丰富，优势物种是好氧细菌，复合菌系F2的物种组成较单一，培养后期具有较高比例的厌氧纤维素分解菌；培养前4天，复合菌系F1和F2的优势物种均为Unclassified Bacillales和Bacillus；第4天之后，不同复合菌系的优势物种及丰度出现差异，F1的优势物种主要属于Bacteroidetes，F2的优势物种主要属于Firmicutes；虽然Petrimonas和Pusillimonas是培养后期的共有优势物种，但是Petrimonas在复合菌系F2中的相对丰度（38.30%）显著高于F1（9.47%），且培养第8天的F2中的Clostridiales OPB54增加至14.85%。[结论] cel48基因拷贝数变化与秸秆纤维素的降解效率、外切纤维素酶活性变化具有一定的相关性，cel48基因可作为潜在的生物分子标记监测秸秆纤维素的降解过程；微生物群落结构对秸秆纤维素的降解效率具有显著影响，Unclassified Bacillales，Bacillus，Petrimonas，Pusillimonas是复合菌系F1和F2降解秸秆纤维素过程中的重要物种。

Abstract:

[Objective] To study the relationship between microbial community and degradation rate of rice straw, we compared and analyzed cellulose-decomposing ability, microbial community structures and shifts of microbial consortia F1 and F2.[Methods] We determined exoglucanase activity by 3, 5-dinitrosalicylic acid colorimetry. We determined content of cellulose, hemicellulose and lignin in rice straw by Van Soest method, and calculated degradation rates of rice straw by the weight changes before and after a 10-day incubation. We analyzed and compared the microbial communities and functional microbiology shifts by clone libraries, Miseq analysis and real time-PCR based on the 16S rRNA gene and cel48 genes.[Results] Total degradation rate, cellulose, and hemicellulose degradation rate of microbial consortia F1 were significantly higher than that of F2. The variation trend of exoglucanase activity in both microbial consortia F1 and F2 was consistent with that of cel48 gene copies. Microbial diversity of F1 was complex with aerobic bacteria as dominant species, whereas that of F2 was simple with a high proportion of anaerobic cellulose decomposing bacteria in the later stage of incubation. In the first 4 days, unclassified Bacillales and Bacillus were dominant in both F1 and F2. The dominant species and abundance became different after 4-day incubation, Bacteroidetes and Firmicutes were dominant phyla of F1 and F2, respectively. Although Petrimonas and Pusillimonas were common dominant species in F1 and F2, abundance of Petrimonas in F2 (38.30%) was significantly higher than that in F1 (9.47%), and the abundance of Clostridiales OPB54 in F2 increased to 14.85% after 8-day incubation.[Conclusion] The abundance of cel48 gene related with cellulose degradation rate and exoglucanase activity, and cel48 gene has the potential as a molecular marker to monitor the process of cellulose degradation. Microbial community structure has a remarkable impact on the degradation efficiency of straw cellulose, and Petrimonas, Paenibacillus, Bacillales, Clostridiales were vital species for microbial consortia F1 and F2 decomposing rice straw.