Study On The Biofiltration Of Bacteria By The Outer Biofilm Of Cicada Flower

In the natural growth process,Cordyceps cicadae can form a mycelium cortices structure specially formed by hyphae,which plays an important role in the growth and development of C.cicadae.In this study,the entomogenous fungus C.cicadae was used as the research material.Through high-throughput sequencing technology,the differences in the bacterial community of the C.cicadae in soil or air environment,as well as,the changes of the bacterial community at different growth stages were understood,and its potential functions were predicted.Then the apparent morphology of the mycelium cortices of C.cicadae growing in soil and air was observed.In order to verify the selective filtration of soil bacteria,the cortices of C.cicadae was used as the filtering medium.Finally,the stable isotope ¹⁵N labeling technology was used to bidirectional labeling of C.cicadae and soil to find out whether the mycelium cortices of C.cicadae has the function of nitrogen transport in the internal and external environment to maintain its nutritional balance.The following results were obtained:(1)A total of 41 phyla,101 classes,202 orders,429 families,953 genera,1785 species and3850 OTUs were detected in the sclerotia and cortices of C.cicadae in different cultivation environments and at different stages.Serratia and Enterococcus were the dominant genera in the C.cicadae at stage of ossified cicada.C.cicadae cultivated in sterile glass bottle at cortices formation stage,Achromobacter and Cedecea were dominant genera in the sclerotia,and Serratia and Pseudomonas were dominant populations in the mycelium cortices.Achromobacter was the dominant bacteria in the sclerotia of C.cicadae during maturity and Serratia was dominant genera in the bacterial community of the mycelium cortices.Pseudomonas was the dominant genus in the sclerotia during the cortices formation period,and Achromobacter was the dominant bacterium during the maturity period.The bacterial community composition of the two phases of the mycelium cortices was similar,mainly composed of Serratia and Streptomyces.The dominant bacterial communities of C.cicadae at different stages in different cultivation environments had their own characteristics.C.cicadae would select environmental bacteria and regulate their own bacterial community structure to maintain the stability of the microecosystem.(2)The results of Venn analysis showed that the abundance of bacterial community increased first and then decreased with the growth and development of C.cicadae.The longer the time of growth in different environments,the greater the difference of bacterial community composition.Among them,22 genera of bacteria such as Achromobacter,Serratia,Pseudomonas,and Cedecea are involved in the whole process of the growth and development of C.cicadae,which are closely related to the growth and development of C.cicadae.Some of them may participate in the infection process of C.cicadae to their hosts,and some may affect the production or content of active substances.The results of PICRUSt showed that most of the potential functional genes were related to metabolism and energy transport,cell behavior and regulation,and played an important role in ontogeny and production of active substances of C.cicadae.(3)Observations on the apparent morphology of the mycelium cortices of C.cicadae showed that the mycelium cortices of C.cicadae showed hydrophobicity,which helped its conidia adhere to the insect epidermis and affected virulence,and was the key to its survival and adaptation.The mycelium cortices of C.cicadae cultivated in aseptic glass bottle was closely arranged,while the cortices of soil covered C.cicadae was disorderly arranged,and the mycelium cortices density of the former was higher than that of the latter,which was related to its growth environment.The"H"type fusion hyphae among the mycelia of C.cicadae is beneficial to gene exchange and signal transduction among its strains or mycelia.(4)The stable isotope ¹⁵N labeling was used to verify the N element transport ability of C.cicadae.The results showed that the mycelia of C.cicadae had a certain ability to transport nitrogen elements,and the mycelia could transfer nitrogen elements inside the worm to the outer mycelium cortices.Aseptic cultivation of C.cicadae mycelium cortices can filter most of the bacteria in the soil.It is speculated that due to the high-density arrangement of mycelium cortices of C.cicadae,it can effectively block the entry of external pathogens into the insect body and ensure itself free from the invasion of external pathogens.There were significant differences in the composition of bacterial communities in different habitats and different dominant bacterial groups in different growth stages.These bacteria played different ecological functions,suggesting that C.cicadae could select environmental microorganisms and regulate its own microbial structure for the benefit of ontogeny.The hydrophobicity of its mycelium cortices,large hyphae density and"H"type fused hyphae are the key factors for its adaptation to the environment and survival.In addition,the absorption and transfer of nitrogen by its hyphae provide nutrition guarantee for its growth,and the selective filtration of bacteria can resist the invasion of pathogens from outside.