圈养大熊猫肠道放线菌菌群多样性及其纤维素降解能力

Diversity and cellulose degradability of intestinal actinobacteria from captive giant panda

以圈养成年大熊猫的粪便为研究对象,采用高通量测序技术和可培养方法,研究圈养大熊猫肠道放线菌种群结构、组成及纤维素降解的功能特性.高通量测序结果显示,在属水平上放线菌属(Actinomyces)(15.52%)、微杆菌属(Microbacterium)(7.06%)、罗氏菌属(Rothia)(6.62%)、分枝杆菌属(Mycobacterium)(5.70%)和棒状杆菌科未鉴定属(unidentified_Corynebacteriaceae)(4.47%)相对丰度较高,性别对成年大熊猫放线菌菌群丰度无显著影响.PCoA分析显示成年大熊猫肠道优势放线菌的种群组成受个体差异的影响较大.Tax4Fun功能预测表明,大熊猫粪便中放线菌功能主要涉及碳水化合物代谢,具有与半纤维素、纤维素代谢相关酶的编码基因.采用2种预处理方法结合4种不同种类的分离培养基从大熊猫粪便中分离放线菌菌株,结果表明采用苯酚对样品进行前处理和分别添加50μg/mL重铬酸钾和制霉菌素的改良高氏一号培养基,分离放线菌的数量及种类最多.通过可培养方法共分离获得96株放线菌,分属于链霉菌属(Streptomyces)、拟无枝菌酸属(Amycolatopsis)、红球菌属(Rhodococcus)、微杆菌属(Microbacterium)、节杆菌属(Arthrobacter)5个属,且上述菌属均在高通量测序中被检测到.功能特性分析结果表明有15株菌株具有纤维素降解酶活性,以链霉菌属为主,且各菌株的β-葡萄糖苷酶(BGL)和外切葡聚糖酶(CBH)酶活较高.本研究表明圈养成年大熊猫肠道中放线菌不仅种类丰富,且部分放线菌具有纤维素降解潜力.

High-throughput sequencing technology and culturing methods were employed to study the population structure,composition,and functional characteristics of cellulose degradation by intestinal actinobacteria in the feces of adult giant pandas in captivity.High-throughput sequencing showed that Actinomyces(15.52%),Microbacterium(7.06%),Rothia(6.62%),Mycobacterium(5.70%),and unidentified_Corynebacteriaceae(4.47%)were the dominant genera,and sex had no significant effect on Actinobacteria abundance.PCoA showed that the population composition of dominant actinobacteria in the intestinal tract of adult giant pandas was greatly affected by individual differences.Tax4Fun function prediction also indicated that actinobacteria in giant panda feces were mainly involved in carbohydrate metabolism and contained genes encoding enzymes related to hemicellulose and cellulose metabolism.Two pretreatment methods,combined with four different types of isolation media,were used to isolate culturable actinobacteria from the feces of adult giant pandas.The result demonstrated that the sample was pretreated by phenol and the highest number and species of actinobacteria were isolated from modified Gause no.1 supplemented with 50μg/mL potassium dichromate and nystatin,respectively.A total of 96 actinobacteria belonging to the following five genera were identified:Streptomyces,Amycolatopsis,Rhodococcus,Microbacterium,and Arthrobacter.These genera were also detected by high-throughput sequencing.Moreover,functional characteristics analysis results showed there were 15 isolates with cellulolytic enzyme activity,mainly belonging to Streptomyces,and most of theirβ-glucosidase and cellobiohydrolase activity was higher than other enzymes.This study revealed that the intestinal actinobacteria of captive adult giant pandas are not only different and abundant but also have the potential for cellulose degradation.