This action funds an NSF Minority Postdoctoral Research Fellowship for FY 2008. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation of underrepresented minorities in biology through mentorship and outreach. The title of the research and training plan for this fellowship to Glenn F. Dulla is "Host-symbiont interactions between composting earthworms and bacteria: Do chemical signaling and motility affect host colonization?" The host institution for this research is the University of Washington and the sponsoring scientist is Dr. David Stahl.
The health of all biological systems is influenced by interactions between the resident micro- and macro-organisms. In terrestrial systems, earthworms improve the health of soil biosystems through their burrowing, ingestion of particles, and nutrient cycling. In turn, the worms'health is enhanced by symbionts such as Acidovorax-like bacteria, which colonize the osmoregulatory-excretory organs (nephridia) of the composting earthworm Eisinia foetida. This project is developing a genetic system to manipulate the genome of the Acidovorax-like species. Using these new tools, genes and expression patterns are being identified that determine the role of bacterial motility and chemical signaling in the bacteria's preferential colonization of the nephridia.
The training objectives expand proficiencies in microbiology techniques. Working in a new biological system will add scientific breadth to the repertoire of technical skills and alternative avenues of scientific reasoning. Broader impacts include a better understanding of the relationship between the earthworm and its associated Acidovorax-like bacteria, as well as more general interactions between eukaryotic hosts and their bacterial endosymbionts.
Work accomplished in this project represents a significant breakthrough in the development of a new model system for study of beneficial bacterial interactions with host animals. The bacterial symbiont Verminephrobacter eiseniae colonizes the nephridia, osmoregulatory-excretory organs, of the common composting earthworm Eisenia fetida. Directed bacterial migration into specific host tissue occurs early in embryonic development. We successfully developed methods for genetic manipulation of V. eiseniae. Use of targeted gene mutagenesis established that two modes of bacterial motility, flagella and type four pili-mediated, are required during early colonization events. These results present the first known molecular mechanisms required for this symbiosis. The results are of broad interest and importance because, in comparison to pathogens, few model systems are available to study mechanisms of beneficial bacterial colonization and maintenance in hosts. Comprehension of complex biological systems is based in research of experimentally tractable model systems. Few beneficial symbiotic systems currently possess the ability to genetically manipulate the bacterial partner to determine molecular mechanisms of initiation, establishment and maintenance of bacteria in appropriate host tissues. This project generated foundation knowledge of what we anticipate will be a new model system to explore underlying mechanisms of specific host-microbe interactions. This base has enabled project expansion to include studies of type four pili-mediated natural transformation, biofilm production and osmotic stress tolerance of V. eiseniae. We anticipate that the model and findings will be of interest to developmental biologists, immunologists, and those interested in bacterial symbioses in general. These areas are all related to understanding how animals interact with bacteria, both benign and pathogenic. The research and training plan sought to broaden participation of underrepresented minorities in biology through mentorship and outreach. Research activities have relied heavily on the training and mentoring of several young scientists which included women and ethnic minorities. This fellow’s training enabled both expanded proficiency in microbiology techniques and personal growth as a senior level scientist. Teaching opportunities included lectures in graduate-level classes and public outreach involving interactive demonstrations for urban middle school children.
