The cultivable gut bacteria Enterococcus mundtii promotes early-instar larval growth of Conogethes punctiferalis via enhancing digestive enzyme activity.

Background: Gut bacteria are crucial in influencing insect development and even phenotypic plasticity. The yellow peach moth Conogethes punctiferalis, as a significant borer pest, has been the subject of limited reports regarding the structural and diversification changes in its gut microbiota during feeding, and their potential impacts on the growth and development of the host insects.

Results: This study, employing 16S rRNA sequencing, demonstrates distinct shifts in the larvae gut microbiome of C. punctiferalis between different feeding stages, highlighting a pronounced diversity in the early-instar with Enterococcus as a predominant genus in laboratory populations. Through in vitro cultivation and sequencing, three bacterial strains - Micrococcus sp., Brevibacterium sp. and Enterococcus mundtii - were isolated and characterized. Bioassays revealed that E. mundtii-infused corn significantly boosts early-instar larval growth, enhancing both body length and weight. Quantitative PCR and spectrophotometry confirmed a higher abundance of E. mundtii in younger larvae, correlating with increased digestive enzyme activity and total protein levels.

Conclusion: This study reveals the heightened gut microbiota diversity in early instars of C. punctiferalis larvae, highlighting that Enterococcus represent a predominant bacteria in laboratory populations. In vitro cultivation and bioassays unequivocally demonstrate the significant role of the cultivable gut bacteria E. mundtii in promoting the growth of early-instar larva. These findings provide a solid theoretical foundation for advancing the comprehension of the intricate interactions between gut microbiota and insect hosts, as well as for the development of eco-friendly pest control technologies based on targeted manipulation of insect gut microbial communities. © 2024 Society of Chemical Industry.