Dynamic Alterations of the Gut Microbiota of Silkworms (Bombyx mori) Inoculated with Cordyceps militaris

Cordyceps militaris is a well-known edible and medicinal entomopathogenic fungus that can be cultivated using silkworm larvae as hosts. However, no reports have been found regarding the gut microbiota of silkworms (Bombyx mori) following C. militaris injection. Based on three biological replicates, illumina 16S rRNA gene sequencing was used to investigate the changes over time in the gut bacteria and fungi of silkworms injected with C. militaris. The results indicated that following inoculation with C. militaris, the abundance of Bacillales and Basidiomycetes increased, while that of Pseudomonadales and Ascomycetes decreased. The abundance of Mammaliicoccus increased by 78% and 26% in dying silkworms compared to their pre-inoculated counterparts and blank control group, respectively. The relative abundance of Rhodotorula in dying silkworms was 2.89-fold and 80.51-fold higher than that in the pre-inoculation group and blank control group, respectively. After inoculation with C. militaris, fungi showed the greatest community variations at day 2, while bacteria displayed the most distinct differences at day 4. Under C. militaris infection, the abundance of all four pathways of Genetic Information Processing in silkworm larvae’s gut microbiota significantly increased. Taken together, the results demonstrate that inoculation with C. militaris induced significant alterations in the composition, structure, assembly, and predictive functional profiles of gut bacteria and fungi in silkworms. This study provides a theoretical basis for exploring the production of C. militaris using silkworm larvae as insect hosts.