Symbiotic bacteria impact numerous aspects of host biology. One major question is the role of early colonizing symbionts (hereafter referred to as pioneer symbionts) in primordial host development and microbial community recruitment and cohesiveness. In contrast to the diverse microbial consortia harbored within the digestive tracts of omnivorous organisms, the crop of the blood-feeding European medicinal leech (Hirudo verbana) contains a predominantly two-member microbial community consisting of the Proteobacteria Aeromonas veronii and the Bacteroidetes Rikenella sp.. The leech digestive system has a simple morphology and limited immunological capabilities. These characteristics combined with the available genetic tools make it an experimentally accessible model system to examine fundamental aspects of symbiosis. This project examines the role of the pioneer symbiont A. veronii in influencing host embryogenesis and preparing the digestive tract for the later colonizing Rikenella. Using microscopic techniques and gene expression analyses, the work will characterize the colonization and proliferation of A. veronii during host oral and gastrointestinal development. Comparative studies of symbiotic and aposymbiotic (i.e. devoid of pioneer symbionts) leeches will investigate the extent to which A. veronii influences host morphological, physiological and functional maturation as well as microbial community dynamics.
The broader impacts of this research include the integrative training of graduate and NSF Robert NOYCE pre-service teaching undergraduates, as well as high school students representing traditionally underrepresented groups in the sciences. To expose the community at large to the significant implications of symbiosis towards biodiversity, prominent scientists in symbiosis research will be incorporated into a university-wide seminar series. The results of this research will be disseminated at various meetings, in publications and publicized on the Rio laboratory website. Lastly, a teaching outcome will be incorporated into classroom environments.
