Different Cultivation Environments Affect the Yield, Bacterial Community and Metabolites of Cordyceps cicadae

Abstract

Cordyceps cicadae is an entomogenous fungus with important uses in traditional Chinese medicine. However, its wild resources have not met consumers’ demand due to excessive harvesting practices. Artificial cultivation is therefore an important alternative, but research on cultivating C. cicadae in natural habitats has not been reported. In this study, we aimed to explore the viability of cultivating C. cicadae in a natural habitat, in the soil of Pinus massoniana forest. We assessed and compared the yield, metabolite contents and bacterial community composition of C. cicadae grown in the Antheraea pernyi pupae at different growth stages, and under different cultivation conditions, in the soil of a natural habitat and in sterile glass bottles. Our results showed that cultivating C. cicadae in a natural habitat is feasible, with up to 95% of pupae producing C. cicadae fruiting bodies. The content of nitrogen compounds (amino acids) in C. cicadae cultivated in a natural habitat was significantly higher than in glass bottles, while the yield and carbon compound (mannitol and polysaccharide) and nucleoside (cordycepin and adenosine) contents were lower. Different bacterial genera were enriched in C. cicadae at different growth stages and cultivation environments, and these bacterial genera were closely related to metabolites contents during growth. This study demonstrated the viability of a novel cultivation method of C. cicadae, which could be used as an alternative to wild stocks of this fungus. These findings provided new insights into the growth mechanism of C. cicadae and its interaction with soil microorganisms.

Analysis of Internal and External Microorganism Community of Wild Cicada Flowers and Identification of the Predominant Cordyceps cicadae Fungus

“…Compared with that of Isaria , the relative abundance of other fungal genera was very low, indicating the strong competition between C. cicadae and other fungi. Similar to previously published research, that C. cicadae injects into the pupae may inhibit some bacterial genera ( Zeng et al, 2021 ). Among the bacteria, the dominant genera Allorhizobium–Neorhizobium–Pararhizobium–Rhizobium , Enterobacteriaceae, Stenotrophomonas , Pandoraea , and Chitinophaga attracted our attention.…”

“…These genera occupied more than 29 and 50% in the coremia and sclerotia, respectively, and less than 1% in soil. Allorhizobium–Neorhizobium–Pararhizobium–Rhizobium , belonging to non-cyanobacteria diazotrophic genera that are known to be associated with plant roots ( You et al, 2021 ), was the dominant genus in the sclerotia and coremia, which might support the previous speculation that cicada flower may exchange carbon and nitrogen elements in soil via endophytic bacteria to affect the content of carbon and nitrogen compounds in cicada flower ( Zeng et al, 2021 ). A previous study found that four strains of Enterobacteriaceae isolated from wild cicada flower can inhibit C. cicadae on PDA medium and increase the yield of fungal metabolites of C. cicadae ( Qu et al, 2019 ), and Enterobacteriaceae may play an important role in host fitness by resisting pathogenic microbes ( Hu et al, 2020 ), so we speculated that Enterobacteriaceae might have an inhibitory effect on C. cicadae and may help C. cicadae to resist other pathogens.…”

“…Although high-throughput sequencing has been used to explore the microbial community associated with Ophiocordyceps sinensis ( Zhang et al, 2010 ; Xia F. et al, 2016 ; Shao et al, 2019 ; Xia et al, 2019 ), only a few papers investigated the bacterial and fungal communities inhabiting cicada flower. Previous researches have revealed that cicada flowers enrich abundant microbial communities ( Chunyu et al, 2019 ; Qu et al, 2019 ; Mou et al, 2020 ; Zeng et al, 2021 ), and the microbial community composition varies with the geographic area ( Chunyu et al, 2019 ), and the endophytic bacteria in cicada flowers can influence the metabolite production ( Qu et al, 2019 ). These results suggested that wild cicada flower populations are ecologically linked to the surrounding soil through microorganisms, which may impact cicada flower growth and production of metabolites.…”

“…Therefore, in order to meet the enormous demand in the market, artificial cultivation of cicada flowers has become a focus of research. Moreover, cultivating cicada flowers in natural habitat soil was proved to be feasible ( Zeng et al, 2021 ), but there are no systematic studies focused on the growth environment of cicada flower. Therefore, it is of great significance to explore the growth mechanism and growth environment of cicada flower.…”

Possible impacts of the predominant Bacillus bacteria on the Ophiocordyceps unilateralis s. l. in its infected ant cadavers

“…The biological properties associated with an outbreak of B. cereus/thuringiensis suggest potential benefits to O. unilateralis s. l . The sympatric bacteria have recently been noted to play crucial roles in the growth of parasitoid fungi 65 – 67 . However, the proliferation of B. cereus/thuringiensis appears coincidental rather than the result of long-term coevolution.…”