Role of gut commensal bacteria in juvenile developmental growth of the host: insights from Drosophila studies.

The gut microbiome plays a crucial role in maintaining health in a variety of organisms, from insects to humans. Further, beneficial symbiotic microbes are believed to contribute to improving the quality of life of the host. Drosophila is an optimal model for studying host-commensal microbe interactions because it allows for convenient manipulation of intestinal microbial composition. Fly microbiota has a simple taxonomic composition and can be cultivated and genetically tracked. This permits functional studies and analyses of the molecular mechanisms underlying their effects on host physiological processes. In this context, we briefly introduce the principle of juvenile developmental growth in Drosophila. Then, we discuss the current understanding of the molecular mechanisms underlying the effects of gut commensal bacteria, such as Lactiplantibacillus plantarum and Acetobacter pomorum, in the fly gut microbiome on Drosophila juvenile growth, including specific actions of gut hormones and metabolites in conserved cellular signaling systems, such as the insulin/insulin-like (IIS) and the target of rapamycin (TOR) pathways. Given the similarities in tissue function/structure, as well as the high conservation of physiological systems between Drosophila and mammals, findings from the Drosophila model system will have significant implications for understanding the mechanisms underlying the interaction between the host and the gut microbiome in metazoans.