Mono-Association with Lactobacillus plantarum Disrupts Intestinal Homeostasis in adult Drosophila.

The microbiome of Drosophila promotes intestinal stem cell division through evolutionarily conserved biochemical pathways. As such, axenic flies have lower rates of gut stem cell division than age-matched wild type counterparts. Additionally, flies with a full consortium of symbiotic bacteria are shorter lived than those maintained in the absence of a microbiome. However, we do not know if stem cell division is essential for symbiont-dependent regulation of adult fly lifespan. To determine if individual symbionts cause aging-dependent death in Drosophila, we examined the impacts of common symbionts on host longevity. In this study, we found that mono-association of adult Drosophila with Lactobacillus plantarum, a widely reported fly symbiont, and member of the probiotic Lactobacillus genus, curtails adult longevity relative to germ-free counterparts. However, the effects of plantarum on lifespan were independent of intestinal aging. Instead, we found that association with plantarum causes an extensive intestinal pathology within the host, characterized by loss of intestinal stem cells, impaired epithelial renewal, and a gradual erosion of epithelial integrity. Our study uncovers an unknown aspect of Lactobacillus plantarum-Drosophila interactions, and establishes a simple model to characterize symbiont-dependent disruption of intestinal homeostasis.