Barnes, Aaron Michael Tolo2012-12-182012-12-182012-11https://hdl.handle.net/11299/141245University of Minnesota Ph.D. dissertation. November 2012. Major: Microbiology, Immunology and Cancer Biology. Advisor: Dr. Gary Dunny. 1 computer file (PDF); xii, 128 pages, appendices 1-2.Enterococcus faecalis is a highly adaptable, gram-positive bacterium that occupies a diverse range of ecological niches. A common soil-dwelling organism, it is also inhabits the metazoan gastrointestinal tract—from insects to humans. E. faecalis is remarkably resistant to a wide range of clinically-relevant antibiotics and readily forms biofilms on both abiotic and biotic surfaces. These latter factors underlie the medical relevance of E. faecalis. This thesis explores the ramifications of early developmental events in E. faecalis biofilm formation. Using correlative microscopy techniques, we investigated a series of mutants with ultrastructural changes in the extracellular matrix that elucidate the roles these genes play in matrix architecture. We also report that extracellular DNA plays a substantial role in stabilizing early (< 8 hr post-inoculation) E. faecalis biofilms, and that the source of this DNA is not via bulk cell lysis, but rather appears to be secreted from metabolically active cells. A putative model for this non-canonical source of DNA in the matrix is also proposed.en-USBiofilmEnterococcus faecalisExtracellular DNAImmunoelectron microscopyMatrixScanning electron microscopyThesis or Dissertation