长足大竹象消化道不同分段菌群异质性及竹木质纤维素降解能力

【目的】长足大竹象Cyrtotrachelus buqueti消化道共生菌群参与了竹纤维素的降解。本研究旨在揭示长足大竹象幼虫消化道不同分段共生菌群异质性及木质纤维素的降解能力。【方法】通过对16S rRNA测序对长足大竹象幼虫消化道分段口器(YB)、前肠(YFG)、中肠(YMG)和后肠(YHG)进行菌群组成分析及功能预测；分析各消化道分段核心属细菌基因组中碳水化合物活性酶(carbohydrate active enzyme, CAZy)基因，预测木质纤维素降解能力；应用口器混合菌(MPJ)、前肠混合菌(FJ)、中肠混合菌(MJ)和后肠混合菌(HJ)悬液体外降解竹笋粉，检测共生菌群的木质纤维素的降解能力。【结果】长足大竹象幼虫消化道菌群多样性分析显示，YFG, YMG和YHG的菌群多样性大于YB，YFG的菌群物种多样性最高，而YB最低。YFG, YMG和YHG样本中厚壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)和变形菌门(Proteobacteria)相对丰度最高，而YB中变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和放线菌门(Actinobacteria)相对丰度最高。核心属细菌基因组CAZy基因分析表明长足大竹象幼虫消化道中大多数细菌基因组中存在丰富的CAZy基因，且在拟杆菌属Bacteroides细菌基因组中尤为明显，预示其与木质纤维素的降解密切相关。体外降解竹笋粉实验结果表明，长足大竹象幼虫MPJ, FJ, MJ和HJ对竹笋粉纤维素的降解率分别为21.7%， 39.9%， 44.2%和21.0%，对半纤维素降解率分别为72.7%， 52.3%， 65.7%和61.5%，对木质素降解率分别为20.5%， 41.3%， 39.9%和37.9%。【结论】长足大竹象幼虫的消化道菌群的异质性可以影响木质纤维素降解能力，因而这些菌群可以作为分离高效木质纤维素降解菌的重要来源之一。本研究为竹生物质的工业转化利用提供部分参考信息。

Heterogeneity and bamboo lignocellulose degradation ability of microbiota in different sections of the alimentary canal of Cyrtotrachelus buqueti (Coleoptera: Curculionidae)

【Aim】 Symbiotic microbiota in the alimentary canal of Cyrtotrachelus buqueti participate in the degradation of bamboo lignocellulose. This study aims to reveal the heterogeneity and lignocellulose degradation ability of symbiotic microbiota in different sections of the alimentary canal of larval C. buqueti. 【Methods】 The composition analysis and functional prediction of microbiota in different sections of the alimentary canal including mouthpart (YB), foregut (YFG), midgut (YMG) and hindgut (YHG) of larval C. buqueti were carried out using 16S rRNA sequencing. The carbohydrate active enzyme (CAZy) genes in the genomes of bacteria belonging to core genera in each alimentary canal section were analyzed to predict the lignocellulose degradation ability. The liquid suspensions of mouthpart mixed bacteria (MPJ), foregut mixed bacteria (FJ), midgut mixed bacteria (MJ) and hindgut mixed bacteria (HJ) of C. buqueti larva were used to degrade bamboo shoot particles in vitro and to verify their lignocellulose degradation ability. 【Results】 The diversity analysis of microbiota in the alimentary canal of larval C. buqueti showed that the diversity of microbiota from YFG, YMG and YHG were higher than that from YB, and the species diversity of microbiota from YFG was the highest, while that of YB was the lowest. In YFG, YMG and YHG samples, Firmicutes, Bacteroidetes and Proteobacteria showed the highest relative abundance, while Proteobacteria, Firmicutes and Actinobacteria were the most abundant in YB. The analysis of CAZy genes in the genomes of bacteria belonging to core genera showed that most microbial genomes in the alimentary canal of larval C. buqueti contain abundant CAZy genes, especially in that of the genus Bacteroides, indicating their relationship with lignocellulose degradation. The experiment results of in vitro bamboo shoot particle degradation by MPJ, FJ, MJ and HJ of C. buqueti larva showed that their cellulose degradation efficiencies were 21.7%, 39.9%, 44.2% and 21.0%, respectively, their hemicellulose degradation efficiencies were 72.7%, 52.3%, 65.7% and 61.5%, respectively, and their lignin degradation efficiencies were 20.5%, 41.3%, 39.9% and 37.9%, respectively. 【Conclusion】 The heterogeneity of microbiota in the alimentary canal of larval C. buqueti can affect the lignocellulose degradation ability, so the microbiota can be used as one of the important sources for the separation of high.efficiency lignocellulose.degrading bacteria. This study provides some reference information for the industrial transformation and utilization of bamboo biomass.