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

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.