The goal of this project is to better understand the functions of symbiotic bacteria that live in earthworm kidneys. This project will be focusing on the composting earthworm, Eisenia fetida. Earthworms play an important role in soil ecosystems, breaking down organic matter, aerating the soil, and enriching soil with nutrients beneficial for plants. Many earthworms harbor bacterial symbionts in their osmoregulatory excretory organs, the nephridia, which function like kidneys to manage salt balance and process waste. Two nephridia occur in each segment of the worm (~ 200 nephridia total) with each containing symbiotic bacteria. Eisenia fetida has three species of bacteria that live within their nephridia: Verminephrobacter eiseniae, a Cytophagales member, and an Actinobacteria. These bacteria are passed into egg capsules from the mother to the next generation. The function of these bacteria is unknown. This project is testing the hypothesis that these bacteria are important for supplementing the diet of the worm. To test this, worms are being cured of their symbionts by treating them with antibiotics during early development to prevent colonization. A colony of cured worms has been established and control and erythromycin-treated stocks will be fed various diets to test their ability to handle a lack of nutrients. Their mortality and fertility will be observed to determine the contribution of the nephridial bacteria to the success of E. fetida. We expect that treated worms will have higher mortality than the control group.