基因组 DNA 去甲基化能够激活沉默基因，改变次级代谢产物谱，是一种全新的菌种改良途径。利用不同浓度的DNA 甲基化酶抑制剂5-氮杂胞苷（5-azaC）处理蛹虫草菌株 CM-L1，降低基因组 DNA 甲基化水平，高效液相色谱筛检得到改良株 LB-C3和 LD-A7，菌丝体中虫草素含量分别提升127%和144.3%。LD-A7不能形成子实体，推测与关键的 DNA 甲基化修饰作用被改变有关。经5次继代培养后，以虫草素含量为指标考察性状稳定性。随传代次数增加，基因组中甲基化的 DNA 含量增加，液体发酵菌丝体中的虫草素含量均显著降低，但是子实体中虫草素含量非常稳定，改良的菌株更适合栽培生产而非工业发酵。%Genomic DNA demethylation may activate silenced gene,which alters secondary metabolite spectrum,and therefore it is a completely novel approach for strain improvement. Using different concentrations of DNA methyltransferase inhibitor 5-azacytidine(5-azaC)to treat the Cordyceps militaris CM-L1,then the genomic DNA methylation level reduced. Further,the improved strains LB-C3 and LD-A7 were acquired by screening with high performance liquid chromatography,and in which the contents of cordycepin in mycelium increased by 127% and 144.3% respectively. LD-A7 could not form a fruiting body,which was speculated to be related to the role of DNA methylation changed. The stability was investigated after 5 times subculture using the content of cordycepin as an indicator. With the subculture times increased, the methylated DNA in the genome increased,and the cordycepin in mycelium of liquid fermentation significantly decreased ;however, the content of cordycepin in fruiting bodies was very stable,indicating that improved strains were better suited to the cultivation rather than production in industrial fermentation.
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