Most plants and animals, including humans, have beneficial bacterial partners that are necessary to enhance health, yet most information about bacterial interactions with hosts is based on pathogen studies. Earthworms, keystone members of the soil system, offer an experimental model for colonization of animal hosts by beneficial bacteria. A common composting worm, Eisenia fetida, maintains bacteria within kidney-like organs and deposits these symbiotic bacteria into egg capsules to colonize earthworm embryos. This study investigates mechanisms that enable bacterial symbionts to detect, migrate into and colonize a particular organ of their host during early development. Crucial elements for the success of both pathogens and beneficial bacteria are the targeting of and attachment to appropriate tissue, followed by subsequent growth. Information about bacterial colonization gained in this study will better equip scientists and medical professionals to combat disease and promote beneficial microbes. The study has several goals: to (1) determine genes involved, (2) identify sensory mechanisms used by symbiotic bacteria to locate tissue, and (3) identify cell surface features of the host to which bacteria bind. Approaches include genetics to analyze gene function, and biochemistry and cell staining methods to identify cell surface proteins and sugars. This work will reveal key mechanisms beneficial bacterial use to successfully colonize the correct tissue. Genomic data generated by this work will be available through appropriate public gene databases. Findings will be published in a timely manner and updated on the lab website. Activities include education of young scientists, including women, and public outreach in the form of hands-on demonstrations for children in grades 3-8, and webpage updates for both experienced scientists and the public. This research will impact a range of scientific disciplines including developmental biology, pathobiology, and soil ecology.
