一种与蝉花易混淆虫草的鉴定及内菌核细菌群落分析

Identification of a Cordyceps easily confused with Isaria cicadae Miquel and analysis of bacterial community in sclerotia

摘要:

【背景】中国浙江省民间常将一种称为“雄蝉花” (也称独角龙)的虫草误认为是雌蝉花(Isaria cicadae Miquel)的同种，因此有必要为二者作出区分。【目的】通过形态、rDNA ITS序列比较蝉花和独角龙的差异，为2种虫草的鉴别提供理论依据；探究二者内菌核细菌群落组成及功能，加深对2种虫草的理解。【方法】通过分离纯培养技术获得蝉花和独角龙菌株；显微镜观察比较2种真菌产孢细胞的形态特征；通过高通量测序技术检测内菌核细菌群落组成并进行功能分析。【结果】经鉴定，蝉花为蝉棒束孢(Isaria cicadae)，独角龙为独角龙弯颈霉(Tolypocladium dujiaolongae)；在细菌属水平上，蝉花内菌核优势细菌属为无色杆菌属(Achromobacter)、Diplorickettsiaceae未定名属和根瘤菌属(Rhizobium)，独角龙弯颈霉内菌核细菌有鞘氨醇杆菌属(Sphingobacterium)、沙雷氏菌属(Serratia)等潜在病原菌属；蝉花和独角龙弯颈霉细菌COG数据库预测功能相似，KEGG Pathway丰度相近。内菌核细菌群落涉及24种基因功能家族，其功能大多与转运和代谢相关，其中与新陈代谢相关的丰度最大。【结论】蝉花和独角龙是不同的物种，而且内菌核细菌群落组成差异较大，细菌主要参与2种虫草的代谢过程；独角龙弯颈霉内菌核存在病原性细菌类群，食用独角龙弯颈霉同食用蝉花相比安全性有待研究。

Abstract:

[Background] In Zhejiang province, China, the male form of cicada that is called the “male cicada flower” (Dujiaolong) is more often identified as female form (Isaria cicadae Miquel). So, it is necessary to distinguish them. [Objective] The theoretical basis for the identification of Isaria cicadae Miquel and Dujiaolong is provided by the difference of morphology and rDNA ITS sequence. Meanwhile, to further understand these two species, we analyzed the composition and function of bacterial community in sclerotia. [Methods] Technology of strains extraction and purification was conducted to obtain Isaria cicadae Miquel and Dujiaolong. Morphological characteristics of the cells which sporulate spores from these two entomopathogenic fungi were identified by microscope. With the technology of high-throughput sequencing, we analyzed the composition and function of bacterial community in sclerotia. [Results] The “cicada flower” (Chan-hua) was identified as Isaria cicadae, Dujiaolong was identified as Tolypocladium dujiaolongae. At the level of bacterial genus, the dominant bacteria in the sclerotia of Isaria cicadae Miquel is Achromobacter, a genus that is unclassified in Diplorickettsiacea, Rhizobium. In Tolypocladium dujiaolongae, the sclerotia has some potential pathogenic bacteria (e.g. Sphingobacterium and Serratia). Based on the bacterial COG database, the function of Isaria cicadae and Tolypocladium dujiaolongae was similar to each other. Meanwhile, the KEGG Pathway abundance of Isaria cicadae and Tolypocladium dujiaolongae was close. The 24-functional-gene families of these two species in sclerotia’s bacterial community were closely related to matter translocation and metabolism. The result show that the bacteria were highly related to metastasis. [Conclusion] Isaria cicadae Miquel is different from Dujiaolong. And the composition of bacterial community of these two species in internal sclerotia is different. The bacteria are mainly involved in the metabolic process of the two entomopathogenic fungi. Due to the pathogenic bacteria groups in the sclerotia of Tolypocladium dujiaolongae, the food safety of the “Tolypocladium dujiaolongae” should be skeptical when it is compared with Isaria cicadae Miquel.