中文摘要：

目的从药用植物蛇足石杉分离纯化内生菌，并筛选可以转化乌苏酸的菌株，以期探究利用药用植物内生菌对乌苏酸进行结构修饰和改造的可行性。方法通过组织块法分离内生菌；用薄层色谱检测转化反应的发生；用CTAB法提取转化菌株的基因组DNA，PCR技术对其ITSrDNA进行扩增，再经Blast比对鉴定菌株。结果从药用植物蛇足石杉的茎和叶中分离得到内生菌52株，用30株对乌苏酸进行转化筛选。有4株内生菌具有转化乌苏酸的能力，经表观形态及分子生物学的方法鉴定转化菌株，分别是Pestalotiopsis microspora , Colletotrichum gloeosporioides , Fusarium chlam ydosporum ,Arthrinium. Sp.结论从转化产物的结构可以得出结论，利用药用植物内生菌对天然活性成分乌苏酸进行微生物转化，可以丰富乌苏酸的结构类型，为获得活性更好的衍生物提供技术和方法基础。

英文摘要：

OBJECTIVE To isolate and purify endophytes from medicinal plant Huperzia serrata and to screen the strains which can modify the structure of ursolic acid. METHODS Endophytes were isolated and purified by tissue segments, and the microbial transformation reactions of ursolic acid were identified by thin-layer chromatography （TLC） ; the genomic DNA of transformation strains were extracted with CTAB method and amplified by PCR, and then compared by blast. RESULTS 52 Endophytes were obtained from the stems and leaves of medicinal plant H. serrata;30 endophytes were screened, among which 4 could microbially transform ursolic acid. The transformation strains were indentified as Pestalotiopsis microspora, Colletotrichum gloeosporioides, Fusarium chlamydosporum, Arthrinium. Sp based on the morphological characteristics and ITS rDNA sequences. CONCLUSION Through the structures of the biotransformation products we can conclude that the microbial transformation of ursolic acid by enophytic fungi strains from H. serrata can diversify the structure of ursolic acid. The work in this paper paved the technical and methodological way for biotransformation of natural compound by endophytic fungi from medicinal plants to obtain derivatives with better activities.