Taxon-Specific Effects of Lactobacillus on Drosophila Host Development

Commensal microbiota heavily influence metazoan host physiology. Drosophila melanogaster has been proven a valuable animal model for studying many aspects of host-microbiota interaction. Lactobacillus are the most common human probiotics and are also one of the major symbiotic bacteria in Drosophila. Although the beneficial effects of Lactobacillus on fly development and physiology have been recognized, how broadly these effects are observed across the Lactobacillus taxa remains largely unknown. In this study, four Lactobacillus species including five strains of L. plantarum were examined for their effects on fly larval development. Monoassociation of germ-free flies with L. rhamnosus (GG) most strongly accelerated fly larval development. Monoassociation with L. plantarum moderately accelerated fly development, but monoassociation with L. reuteri or L. sakei had marginal effects, despite similar bacterial loads in the host gut. An L. plantarum strain previously isolated from our lab rarely enhanced larval development, confirming the strain-specific effects of L. plantarum. The correlation between development-promoting effects and protein digestion activity in the host gut was found only among the members of L. plantarum species. Moreover, the cytoprotective response in the host gut known to be induced by L. plantarum was not correlated with development-promoting effects among any of the bacteria tested. Our results suggest that a broad range of Lactobacillus taxa are able to reside in the fly gut, but their ability to enhance host larval development is highly varied. This study may aid our understanding of the basic principles underlying the beneficial effects of probiotic commensal bacteria on metazoan development.