Infection of Ophiocordyceps sinensis Fungus Causes Dramatic Changes in the Microbiota of Its Thitarodes Host

Ascarosides and Symbiotic Bacteria of Entomopathogenic Nematodes Regulate Host Immune Response in Galleria mellonella Larvae

Insects protect themselves through their immune systems. Entomopathogenic nematodes and their bacterial symbionts are widely used for the biocontrol of economically important pests. Ascarosides are pheromones that regulate nematode behaviors, such as aggregation, avoidance, mating, dispersal, and dauer recovery and formation. However, whether ascarosides influence the immune response of insects remains unexplored. In this study, we co-injected ascarosides and symbiotic Photorhabdus luminescens subsp. kayaii H06 bacteria derived from Heterorhabditis bacteriophora H06 into the last instar larvae of Galleria mellonella. We recorded larval mortality and analyzed the expressions of AMPs, ROS/RNS, and LPSs. Our results revealed a process in which ascarosides, acting as enhancers of the symbiotic bacteria, co-induced G. mellonella immunity by significantly increasing oxidative stress responses and secreting AMPs (gallerimycin, gloverin, and cecropin). This led to a reduction in color intensity and the symbiotic bacteria load, ultimately resulting in delayed host mortality compared to either ascarosides or symbiotic bacteria. These findings demonstrate the cross-kingdom regulation of insects and symbiotic bacteria by nematode pheromones. Furthermore, our results suggest that G. mellonella larvae may employ nematode pheromones secreted by IJs to modulate insect immunity during early infection, particularly in the presence of symbiotic bacteria, for enhancing resistance to invasive bacteria in the hemolymph.

The composition and function of bacterial communities in Bombyx mori (Lepidoptera: Bombycidae) changed dramatically with infected fungi: A new potential to culture Cordyceps cicadae

Cordyceps cicadae (Hypocreales: Cordycipitaceae) is a renowned entomopathogenic fungus used as herbal medicine in China. However, wild C. cicadae resources have been threatened by heavy harvesting. We hypothesised that Bombyx mori L. (Lepidoptera: Bombycidae) could be a new alternative to cultivate C. cicadae due to the low cost of rearing. Bacterial communities are crucial for the formation of Cordyceps and for promoting the production of metabolites. To better understand the bacterial community structure associated with Cordyceps, three Claviciptaceae fungi were used to explore the pathogenicity of the silkworms. Here, fifth-instar silkworms were infected with C. cicadae, Cordyceps cateniannulata (Hypocreales: Cordycipitaceae) and Beauveria bassiana (Hypocreales: Cordycipitaceae). Subsequently, we applied high-throughput sequencing to explore the composition of bacterial communities in silkworms. Our results showed that all three fungi were highly pathogenic to silkworms, which suggests that silkworms have the potential to cultivate Cordyceps. After fungal infection, the diversity of bacterial communities in silkworms decreased significantly, and the abundance of Staphylococcus increased in mummified larvae, which may play a role in the death process when the host suffers infection by entomopathogenic fungi. Furthermore, there were high similarities in the bacterial community composition and function in the C. cicadae and C. cateniannulata infected samples, and the phylogenetic analysis suggested that these similarities may be related to the fungal phylogenetic relationship. Our findings reveal that infection with different entomopathogenic fungi affects the composition and function of bacterial communities in silkworms and that the bacterial species associated with Cordyceps are primarily host dependent, while fungal infection affects bacterial abundance.

Unearthing diverse culturable fungal communities associated with Ophiocordyceps indica sp. nov. from Indian Western Himalaya

Fungal communities colonizing Ophiocordyceps spp. plays a crucial ecological role in their natural habitat, contributing to infect the host larvae, and influencing their occurrence. Although associated fungi with the newly described Ophiocordyceps indica, from the Indian Western Himalaya remains unclear. Therefore, we untangled the culturable fungal communities associated with O. indica and soil adhered to it, collected from low-height areas of Himachal Pradesh, India. The study resulted in the identification of 111 fungal isolates representing 17 families, with maximum fungal isolates (36.03%) within Cordycipitaceae. Interestingly, a total of 24 genera were found associated with O. indica and adhered soil, of which 12 were common, 8 were exclusive to O. indica and 4 were only limited to soil. Additionally, the influence of soil physicochemical parameters on fungal diversity indices revealed a positive correlation with humidity and available nitrogen and a negative correlation with pH and available phosphorus. These findings provide insights into the culturable fungal diversity of O. indica and the soil adhering to it, thus can contribute to the understanding of host-microbial interactions. Furthermore, these associations can be explored as a source of bioactive metabolites to combat the unending industrial demands.

Cladosporium-Insect Relationships

The range of interactions between Cladosporium, a ubiquitous fungal genus, and insects, a class including about 60% of the animal species, is extremely diverse. The broad case history of antagonism and mutualism connecting Cladosporium and insects is reviewed in this paper based on the examination of the available literature. Certain strains establish direct interactions with pests or beneficial insects or indirectly influence them through their endophytic development in plants. Entomopathogenicity is often connected to the production of toxic secondary metabolites, although there is a case where these compounds have been reported to favor pollinator attraction, suggesting an important role in angiosperm reproduction. Other relationships include mycophagy, which, on the other hand, may reflect an ecological advantage for these extremely adaptable fungi using insects as carriers for spreading in the environment. Several Cladosporium species colonize insect structures, such as galleries of ambrosia beetles, leaf rolls of attelabid weevils and galls formed by cecidomyid midges, playing a still uncertain symbiotic role. Finally, the occurrence of Cladosporium in the gut of several insect species has intriguing implications for pest management, also considering that some strains have proven to be able to degrade insecticides. These interactions especially deserve further investigation to understand the impact of these fungi on pest control measures and strategies to preserve beneficial insects.

Microbial landscapes of the rhizosphere soils and roots of Luffa cylindrica plant associated with Meloidogyne incognita

Introduction

The root-knot nematodes (RKN), especially Meloidogyne spp., are globally emerging harmful animals for many agricultural crops.

Methods

To explore microbial agents for biological control of these nematodes, the microbial communities of the rhizosphere soils and roots of sponge gourd (Luffa cylindrica) infected and non-infected by M. incognita nematodes, were investigated using culture-dependent and -independent methods.

Results

Thirty-two culturable bacterial and eight fungal species, along with 10,561 bacterial and 2,427 fungal operational taxonomic units (OTUs), were identified. Nine culturable bacterial species, 955 bacterial and 701 fungal OTUs were shared in both four groups. More culturable bacterial and fungal isolates were detected from the uninfected soils and roots than from the infected soils and roots (except no fungi detected from the uninfected roots), and among all samples, nine bacterial species (Arthrobacter sp., Bacillus sp., Burkholderia ambifaria, Enterobacteriaceae sp., Fictibacillus barbaricus, Microbacterium sp., Micrococcaceae sp., Rhizobiaceae sp., and Serratia sp.) were shared, with Arthrobacter sp. and Bacillus sp. being dominant. Pseudomonas nitroreducens was exclusively present in the infested soils, while Mammaliicoccus sciuri, Microbacterium azadirachtae, and Priestia sp., together with Mucor irregularis, Penicillium sp., P. commune, and Sordariomycetes sp. were found only in the uninfected soils. Cupriavidus metallidurans, Gordonia sp., Streptomyces viridobrunneus, and Terribacillus sp. were only in the uninfected roots while Aspergillus sp. only in infected roots. After M. incognita infestation, 319 bacterial OTUs (such as Chryseobacterium) and 171 fungal OTUs (such as Spizellomyces) were increased in rhizosphere soils, while 181 bacterial OTUs (such as Pasteuria) and 166 fungal OTUs (such as Exophiala) rose their abundance in plant roots. Meanwhile, much more decreased bacterial or fungal OTUs were identified from rhizosphere soils rather than from plant roots, exhibiting the protective effects of host plant on endophytes. Among the detected bacterial isolates, Streptomyces sp. TR27 was discovered to exhibit nematocidal activity, and B. amyloliquefaciens, Bacillus sp. P35, and M. azadirachtae to show repellent potentials for the second stage M. incognita juveniles, which can be used to develop RKN bio-control agents.

Discussion

These findings provided insights into the interactions among root-knot nematodes, host plants, and microorganisms, which will inspire explorations of novel nematicides.

Depending on different apoptosis pathways, the effector Cscaspase-3 in Chilo suppressalis exposed to temperature and parasitic stress was induced

Apoptosis is a form of programmed cell death (PCD) that is largely triggered by caspases through both the mitochondria-dependent and mitochondria-independent pathways. The rice stem borer, Chilo suppressalis, serves as an economically important pest of rice, which is often suffered by temperature and parasitic stress under natural conditions. In the present study, effector Cscaspase-3 encoding caspase was obtained from the rice pest Chilo suppressalis. CsCaspase-3 possesses p20 and p10 subunits, two active sites, four substrate-binding sites, and two cleavage motifs. Real-time quantitative PCR showed that Cscaspase-3 was expressed at maximal levels in hemocytes; furthermore, transcription was most highly in female adults. Expression of Cscaspase-3 was induced by hot and cold temperatures, with the highest expression at 39 °C. Cscaspase-3 expression was also significantly induced at 10 h, 2 d, 5 d, and 7 d of parasitism. Flow cytometry results showed that both temperature and parasitism trigger apoptosis, but only parasitism induces apoptosis via the mitochondrial apoptosis pathway in C. suppressalis. RNAi-mediated silencing of Cscaspase-3 expression reduced C. suppressalis survival at -3 °C. This study provides a foundation for further studies of caspases in insects during biotic and abiotic stress.

Unraveling the Secrets of a Double-Life Fungus by Genomics: Ophiocordyceps australis CCMB661 Displays Molecular Machinery for Both Parasitic and Endophytic Lifestyles

Ophiocordyceps australis (Ascomycota, Hypocreales, Ophiocordycipitaceae) is a classic entomopathogenic fungus that parasitizes ants (Hymenoptera, Ponerinae, Ponerini). Nonetheless, according to our results, this fungal species also exhibits a complete set of genes coding for plant cell wall degrading Carbohydrate-Active enZymes (CAZymes), enabling a full endophytic stage and, consequently, its dual ability to both parasitize insects and live inside plant tissue. The main objective of our study was the sequencing and full characterization of the genome of the fungal strain of O. australis (CCMB661) and its predicted secretome. The assembled genome had a total length of 30.31 Mb, N50 of 92.624 bp, GC content of 46.36%, and 8,043 protein-coding genes, 175 of which encoded CAZymes. In addition, the primary genes encoding proteins and critical enzymes during the infection process and those responsible for the host-pathogen interaction have been identified, including proteases (Pr1, Pr4), aminopeptidases, chitinases (Cht2), adhesins, lectins, lipases, and behavioral manipulators, such as enterotoxins, Protein Tyrosine Phosphatases (PTPs), and Glycoside Hydrolases (GHs). Our findings indicate that the presence of genes coding for Mad2 and GHs in O. australis may facilitate the infection process in plants, suggesting interkingdom colonization. Furthermore, our study elucidated the pathogenicity mechanisms for this Ophiocordyceps species, which still is scarcely studied.

Plant quercetin degradation by gut bacterium Raoultella terrigena of ghost moth Thitarodes xiaojinensis

Associated microbes of several herbivorous insects can improve insect fitness. However, the contribution of specific insect gut bacterium to plant toxin toxification for its host fitness remains scarce. Here, a gut bacterium Raoultella terrigena from the ghost moth Thitarodes xiaojinensis larvae was identified. This bacterium grew unhindered in the presence of Polygonum viviparum, which is a natural food for ghost moth larvae but showed significant growth inhibition and toxicity against Spodoptera litura. S. litura reared on artificial diets containing 5, 15 and 25% P. viviparum powder after 7 days coculture with R. terrigena were found to have shorter larval and pupal durations than on the diets containing P. viviparum powder but without R. terrigena coculture. HPLC analysis revealed that the content of quercetin in mineral medium containing 15% P. viviparum powder after 7 days coculture with R. terrigena was significantly decreased (79.48%) as compared with that in P. viviparum powder without R. terrigena coculture. In vitro fermentation further verified that R. terrigena could degrade 85.56% quercetin in Lucia-Bertani medium. S. litura reared on artificial diets containing 0.01, 0.05 and 0.1 mg/g quercetin after 48 h coculture with R. terrigena were also found to have shorter larval, prepupal and pupal durations, as well as higher average pupal weight and adult emergence rate than on the diets containing quercetin, but without R. terrigena coculture. In addition, R. terrigena was detected in the bud and root tissues of the sterilized P. viviparum, indicating that T. xiaojinensis larvae might acquire this bacterium through feeding. These results demonstrate that the gut bacteria contribute to the degradation of plant toxic molecules to improve the development of herbivorous insects and provide fundamental knowledge for developing effective methods for beneficial insect rearing and pest control.

Identification and functional analysis of bacteria in sclerotia of Cordyceps militaris

Background

Cordyceps militaris is a fungus that parasitizes insects. Compounds from C. militaris are valuable in medicine and functional food. There are many kinds of bacteria in the natural sclerotia of C. militaris. However, the community structure of microorganisms in samples from different places may be different, and their corresponding ecological functions require experimental verification.

Methods

We used high-throughput sequencing technology to analyze bacterial 16S rRNA gene sequences in sclerotia of three samples of C. militaris from Liaoning Province, China. We isolated, identified and verified the function of culturable bacterial strains from the sclerotia.

Results

Pseudomonas, Pedobacter, Sphingobacterium, and Serratia were the dominant bacterial genera in the sclerotia. And function prediction showed that Pseudomonas and Pedobacter could be heterotrophic, Sphingobacterium could decompose urea, and Serratia could reduce nitrate. Two strains of bacteria isolated from the sclerotia of C. militaris, N-2 and N-26, were identified as Stenotrophomonas maltophilia and Pseudomonas baetica, respectively, based on culture and biochemical characteristics. When these isolated strains were co-cultured with C. militaris, the mycelium biomass and mycelium pellet diameter decreased, and the content of extracellular polysaccharide increased. Strain N-26 decreased the cordycepin content in C. militaris.

Conclusions

Bacteria in sclerotia have an important effect on the growth of C. militaris and the production of its metabolites.

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

Animal hosts infected and killed by parasitoid fungi become nutrient-rich cadavers for saprophytes. Bacteria adapted to colonization of parasitoid fungi can be selected and can predominate in the cadavers, actions that consequently impact the fitness of the parasitoid fungi. In Taiwan, the zombie fungus, Ophiocordyceps unilateralis sensu lato (Clavicipitaceae: Hypocreales), was found to parasitize eight ant species, with preference for a principal host, Polyrhachis moesta. In this study, ant cadavers grew a fungal stroma that was predominated by Bacillus cereus/thuringiensis. The bacterial diversity in the principal ant host was found to be lower than the bacterial diversity in alternative hosts, a situation that might enhance the impact of B. cereus/thuringiensis on the sympatric fungus. The B. cereus/thuringiensis isolates from fungal stroma displayed higher resistance to a specific naphthoquinone (plumbagin) than sympatric bacteria from the environment. Naphthoquinones are known to be produced by O. unilateralis s. l., and hence the resistance displayed by B. cereus/thuringiensis isolates to these compounds suggests an advantage to B. cereus/thuringiensis to grow in the ant cadaver. Bacteria proliferating in the ant cadaver inevitably compete for resources with the fungus. However, the B. cereus/thuringiensis isolates displayed in vitro capabilities of hemolysis, production of hydrolytic enzymes, and antagonistic effects to co-cultured nematodes and entomopathogenic fungi. Thus, co-infection with B. cereus/thuringiensis offers potential benefits to the zombie fungus in killing the host under favorable conditions for reproduction, digesting the host tissue, and protecting the cadaver from being taken over by other consumers. With these potential benefits, the synergistic effect of B. cereus/thuringiensis on O. unilateralis infection is noteworthy given the competitive relationship of these two organisms sharing the same resource.

Interspecific Hybridization and Complete Mitochondrial Genome Analysis of Two Ghost Moth Species

Simple Summary

The Chinese cordyceps is a valuable parasitic Ophiocordyceps sinensis fungus–Thitarodes/Hepialus larva complex. In view of culturing this complex, a method for the artificial rearing of the Thitarodes/Hepialus ghost moth hosts was established. Deterioration of the host insect population and low mummification rates in infected larvae constrain effective cultivation. Hybridization of Thitarodes/Hepialus populations may overcome this problem. Thitarodes shambalaensis and Thitarodes sp. were inbred or hybridized, and the biological parameters, larval sensitivity to the fungal infection and mitochondrial genomes of the resulting populations were investigated. Hybridization of T. shambalaensis and Thitarodes sp. allowed producing a new generation. One hybrid population (T. shambalaensis females mated with Thitarodes sp. males) showed increased population growth as compared with the parental Thitarodes sp. population. The sensitivity of the inbred larval populations to four fungal isolates of O. sinensis differed. The complete mitochondrial genomes of T. shambalaensis, Thitarodes sp. and the hybrid population were 15,612 bp, 15,389 bp and 15,496 bp in length, respectively. A + T-rich regions were variable in sizes and repetitive sequences. The hybrid population was located in the same clade with T. shambalaensis, implying the maternal inheritance of mitochondrial DNA.

Abstract

The Chinese cordyceps, a parasitic Ophiocordyceps sinensis fungus–Thitarodes/Hepialus larva complex, is a valuable biological resource endemic to the Tibetan Plateau. Protection of the Plateau environment and huge market demand make it necessary to culture this complex in an artificial system. A method for the large-scale artificial rearing of the Thitarodes/Hepialus insect host has been established. However, the deterioration of the insect rearing population and low mummification of the infected larvae by the fungus constrain effective commercial cultivation. Hybridization of Thitarodes/Hepialus populations may be needed to overcome this problem. The species T. shambalaensis (GG♂ × GG♀) and an undescribed Thitarodes species (SD♂ × SD♀) were inbred or hybridized to evaluate the biological parameters, larval sensitivity to the fungal infection and mitochondrial genomes of the resulting populations. The two parental Thitarodes species exhibited significant differences in adult fresh weights and body lengths but not in pupal emergence rates. Hybridization of T. shambalaensis and Thitarodes sp. allowed producing a new generation. The SD♂ × GG♀ population showed a higher population trend index than the SD♂ × SD♀ population, implying increased population growth compared with the male parent. The sensitivity of the inbred larval populations to four fungal isolates of O. sinensis also differed. This provides possibilities to create Thitarodes/Hepialus populations with increased growth potential for the improved artificial production of the insect hosts. The mitochondrial genomes of GG♂ × GG♀, SD♂ × SD♀ and SD♂ × GG♀ were 15,612 bp, 15,389 bp and 15,496 bp in length, with an A + T content of 80.92%, 82.35% and 80.87%, respectively. The A + T-rich region contains 787 bp with two 114 bp repetitive sequences, 554 bp without repetitive sequences and 673 bp without repetitive sequences in GG♂ × GG♀, SD♂ × SD♀ and SD♂ × GG♀, respectively. The hybrid population (SD♂ × GG♀) was located in the same clade with GG♂ × GG♀, based on the phylogenetic tree constructed by 13 PCGs, implying the maternal inheritance of mitochondrial DNA.

A Snapshot Picture of the Fungal Composition of Bee Bread in Four Locations in Bulgaria, Differing in Anthropogenic Influence

Information about the fungal composition of bee bread, and the fermentation processes to which the fungi contribute significantly, is rather scarce or fragmentary. In this study, we performed an NGS-based metagenomics snapshot picture study of the fungal composition of bee bread in four locations in Bulgaria during the most active honeybee foraging period at the end of June 2020. The sampling locations were chosen to differ significantly in climatic conditions, landscape, and anthropogenic pressure, and the Illumina 2 × 250 paired-end reads platform was used for amplicon metagenomics study of the ITS2 region. We found that some of the already reported canonical beneficial core fungal species were present within the studied samples. However, some fungal genera such as Monilinia, Sclerotinia, Golovinomyces, Toxicocladosporium, Pseudopithomyces, Podosphaera and Septoriella were reported for the first time among the dominant genera for a honeybee related product. Anthropogenic pressure negatively influences the fungal composition of the bee bread in two different ways-urban/industrial pressure affects the presence of pathogenic species, while agricultural pressure is reflected in a decrease of the ratio of the beneficial fungi.

Stage- and Rearing-Dependent Metabolomics Profiling of Ophiocordyceps sinensis and Its Pipeline Products

Cordyceps, a parasitic complex of the fungus Ophiocordyceps sinensis (Berk.) (Hypocreales: Ophiocordycipitaceae) and the ghost moth Thitarodes (Lepidoptera: Hepialidae), is a historical ethnopharmacological commodity in China. Recently, artificial cultivation of Chinese cordyceps has been established to supplement the dwindling natural resources. However, much is unknown between the natural and cultivated products in terms of nutritional aspect, which may provide essential information for quality evaluation. The current study aims to determine the metabolic profiles of 17 treatments from 3 sample groups including O. sinensis fungus, Thitarodes insect and cordyceps complex, using Gas Chromatography - Quadrupole Time-of-Flight Mass Spectrometry. A total of 98 metabolites were detected, with 90 of them varying in concentrations among groups. The tested groups could be separated, except that fungal fruiting body was clustered into the same group as Chinese cordyceps. The main distinguishing factors for the groups studied were the 24 metabolites involved in numerous different metabolic pathways. In conclusion, metabolomics of O. sinensis and its related products were determined mainly by the fruiting bodies other than culture methods. Our results suggest that artificially cultured fruiting bodies and cordyceps may share indistinguishable metabolic functions as the natural ones.

Improving Hypoxia Adaption Causes Distinct Effects on Growth and Bioactive Compounds Synthesis in an Entomopathogenic Fungus Cordyceps militaris

Cordyceps militaris is an entomopathogenic fungus producing a variety of bioactive compounds. To meet the huge demand for medicinal and edible products, industrialized fermentation of mycelia and cultivation of stromata have been widely developed in China. The content of bioactive metabolites of C. militaris, such as cordycepin, is higher when cultivated on silkworm pupae than on rice or in broth. However, compared with other cultivation methods, C. militaris grows more slowly and accumulates less biomass. The hypoxic environment in pupa hemocoel is one of environmental factor which is not existed in other cultivation methods. It is suggested that hypoxia plays an important role on the growth and the synthesis of bioactive compounds in C. militaris. Here, we demonstrated that the distinct effects on the growth and synthesis of bioactive compounds employing different strategies of improving hypoxia adaption. The introduction of Vitreoscilla hemoglobin enhanced growth, biomass accumulation, and crude polysaccharides content of C. militaris. However, cordycepin production was decreased to 9-15% of the control group. Meanwhile, the yield of adenosine was increased significantly. Nonetheless, when the predicted bHLH transcription factor of sterol regulatory element binding proteins (SREBPs) was overexpressed in C. militaris to improve the hypoxia adaption of fungal cells, cordycepin content was significantly increased more than two-fold. These findings reveal the role of SREBPs on growth and bioactive compounds synthesis. And it also provides a scientific basis for rationally engineering strains and optimization strategies of air supply in cultivation and fermentation.

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

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.

Gut Bacterial and Fungal Communities of the Wild and Laboratory-Reared Thitarodes Larvae, Host of the Chinese Medicinal Fungus Ophiocordyceps sinensis on Tibetan Plateau

Simple Summary

The ghost moth, Thitarodes sp., is an obligate host of the most precious fungus Ophiocordyceps sinensis on Tibetan plateau. Artificial rearing of the ghost moth at low-altitude laboratory by mimicking the environment of the wild habitat for the cultivation of the Chinese cordyceps has been realized. However, the high mortality of ghost moth larvae by pathogens, low and slow infection, and mummification rate by O. sinensis still constrain the efficient cultivation of the Chinese cordyceps. Both larval gut microbiota and their exploitation in the Thitarodes artificial rearing system have attracted a renewed interest. In the present study, the gut bacterial and fungal communities of the wild and laboratory-reared populations were characterized using both culture-dependent and -independent approaches. The discovery of apparent microbial community shifts between the wild and laboratory-reared ghost moth larvae, many opportunistic pathogenic bacteria and fungi in the gut of the laboratory-reared ghost moth larvae, and the dominant bacteria enriched in the wild ghost moth provide interesting cues for selecting beneficial probiotic bacteria to improve the effectiveness of Thitarodes rearing system and the cultivation of the Chinese cordyceps.

Abstract

By employing a culture-dependent and -independent 16S rRNA and ITS gene high-throughput sequencing analyses, comprehensive information was obtained on the gut bacterial and fungal communities in the ghost moth larvae of three different geographic locations from high-altitude on Tibet plateau and from low-altitude laboratory. Twenty-six culturable bacterial species belonging to 21 genera and 14 fungal species belonging to 12 genera were identified from six populations by culture-dependent method. Carnobacterium maltaromaticum was the most abundant bacterial species from both the wild and laboratory-reared larvae. The most abundant OTUs in the wild ghost moth populations were Carnobacteriaceae, Enterobacteriaceae for bacteria, and Ascomycota and Basidiomycota for fungi. Larval microbial communities of the wild ghost moth from different geographic locations were not significantly different from each other but significant difference in larval microbial community was detected between the wild and laboratory-reared ghost moth. The larval gut of the wild ghost moth was dominated by the culturable Carnobacterium. However, that of the laboratory-reared ghost moth exhibited significantly abundant Wolbachia, Rhizobium, Serratia, Pseudomonas, and Flavobacterium. Furthermore, the larval gut of the wild ghost moth had a significantly higher abundance of Ophiocordyceps but lower abundance of Candida and Aspergillus than that of the laboratory-reared ghost moth.