Characterization of DNA Viruses in Hindgut Contents of Protaetia brevitarsis Larvae

The scarab species Protaetia brevitarsis, an edible insect, has been used in traditional medicine, as animal feed, and for converting agricultural organic wastes into biofertilizer. The intestinal tract, which contains a diverse array of microbiota, including viruses, plays a critical role in animal health and homeostasis. We previously conducted a comparative analysis of the gut microbiota of third-instar larvae of P. brevitarsis obtained from five different farms and found significant differences in the composition of the gut bacterial microbiota between farms. To better understand the gut microbiota, the composition of DNA viruses in the hindgut contents of P. brevitarsis larvae obtained from five farms was investigated using metagenomic sequencing in this study. The β-diversity was significantly different between metagenomic data obtained from the five farms (PERMANOVA, pseudo-F = 46.95, p = 0.002). Family-based taxonomic analysis indicated that the relative abundance of viruses in the gut overall metagenome varied significantly between farms, with viral reads comprising approximately 41.2%, 15.0%, 4.3%, 4.0%, and 1.6% of metagenomic sequences from the farms Tohamsan gumbengi farm (TO), Secomnalagum gumbengi (IS), Gumbengi brothers (BR), Kyungpook farm (KB), and Jhbio (JH), respectively. More than 98% of the DNA viruses in the hindgut were bacteriophages, mainly belonging to the Siphoviridae family. At the species level, Phage Min1, infecting the genus Microbacterium, was detected in all farms, and it was the most abundant bacteriophage in intestinal microbiota, with a prevalence of 0.9% to 29.09%. The detected eukaryotic DNA viruses accounted for 0.01% to 0.06% of the intestinal microbiota and showed little or no relationship with insect viruses. Therefore, they most likely originated from contaminated feed or soil. These results suggest that the condition of substrates used as feed is more important than genetic factors in shaping the intestinal viral microbiota of P. brevitarsis larvae. These results can be used as reference data for understanding the hindgut microbiota of P. brevitarsis larvae and, more generally, the gut virome of insects.