基于宏基因组的苜蓿青贮中梭菌菌群结构和功能分析

Metagenomic Structure and Function Analysis of Clostridial Community in Alfalfa Silage

采用宏基因组技术开展了紫花苜蓿单独青贮(对照组)和添加蔗糖(蔗糖组)青贮中梭菌菌群结构及功能分析的研究,结果表明:对照组在青贮56 d后发生严重的丁酸发酵,表现出高的pH值、丁酸和氨态氮含量,而添加蔗糖显著抑制了丁酸发酵。梭菌菌群物种注释表明,对照组青贮中梭菌属相对丰度最大,产气荚膜梭菌和酪丁酸梭菌是优势梭菌种;添加蔗糖降低了产气荚膜梭菌和酪丁酸梭菌的相对丰度,而且产气荚膜梭菌和酪丁酸梭菌的相对丰度与丁酸和氨态氮含量呈极显著正相关(P<0.01)。功能注释表明,碳水化合物代谢是两组青贮中最丰富的代谢类通路,碳代谢是对照组中梭菌基因富集最多的代谢通路,而氮代谢是对照组中氨基酸代谢的关键通路。综上所述,产气荚膜梭菌和酪丁酸梭菌是苜蓿青贮中造成丁酸发酵的关键梭菌,而碳代谢和氮代谢是梭菌菌群参与的主要代谢。

This study used metagenomic sequencing to analyze the clostridial community structure and functional metabolism of alfalfa silage with and without sucrose additive.The results showed that severe butyric acid fermentation occurred in the control group after 56 days of ensiling,as evidenced by high pH,butyric acid and ammonia nitrogen content,while the sucrose group significantly inhibited butyric acid fermentation.The clostridial community structure analysis indicated that Clostridium as the most abundant genus in the control group,with Clostridium perfringens and Clostridium tyrobutyricum being the dominant species.The sucrose additive reduced the relative abundance of C.perfringens and C.tyrobutyricum,and their relative abundance of these species was extremely significantly positively correlated with butyric acid and ammonia nitrogen contents(P<0.01).The functional annotation indicated that carbohydrate metabolism was the most enriched metabolic pathway in both groups,with carbon metabolism being the most enriched metabolic pathway in the control group,and nitrogen metabolism being the key pathway of amino acid metabolism.In conclusion,C.perfringens and C.tyrobutyricum are the critical species responsible for butyric acid fermentation in alfalfa silage,and the carbon and nitrogen metabolism are the main metabolic pathways in which the clostridial community participates.