Bacterial Colonization Dynamics and Ecology of the Developing Zebrafish Intestine
MetadataShow full item record
Human intestinal microbiomes exhibit a large degree of interindividual compositional variation. Animal models, such as the zebrafish, facilitate the design of controlled and highly replicated studies that allow us to understand the normal variation in vertebrate intestinal composition and to study the rules guiding normal assembly of these complex communities. The smaller intestinal size and high fecundity of the zebrafish allow us to fully sample the intestinal contents of many animals, while the optical transparency allows direct in vivo observation of fluorescently labeled bacterial species within the intestine. The studies in this dissertation utilize these advantages to investigate the composition, colonization dynamics and functional requirements for colonization in the vertebrate intestine. We first describe the taxonomic composition and diversity of the zebrafish intestinal microbiota from wild-caught and domesticated zebrafish. In the process, we identify a set of core bacterial genera that are consistently present in zebrafish intestines. We then use species from two of these genera in subsequent studies to gain a detailed understanding of the colonization dynamics and genetic requirements of the two species. We initially describe the application of light sheet microscopy to imaging the zebrafish intestine and associated colonizing bacteria. We find that a single species, Aeromonas veronii, does not occupy the entire intestinal space and that competition within the same species appears to prevent further colonization. These results are extended to a zebrafish isolated Vibrio species as well as A. veronii by tagging bacteria with transposon insertions and tracking the changes in colonizing population sizes. These insertion libraries also identify genes in each bacterial species that are important in the process of colonization, highlighting the key role for motility and chemotaxis in this process. The descriptions and methods discussed in this dissertation advance the use of this important model organism towards the understanding of vertebrate host-microbial interactions. This dissertation includes previously published co-authored material as well as unpublished co-authored material.