Packaging and delivery of plasmids by bacterial extracellular vesicles

2017-07-20Microbial communities prolifically colonize diverse and changing environments across the planet. These populations develop, grow and persist through a wealth of intra and interspecies communications that allow for both cooperation and competition. Microbial ecology is shaped by interactions between bacterial species, ensuring the stability, maintenance and diversification of multicellular communities. The extracellular exchange of molecules between cells, in the form of small molecules, proteins, and even genetic material, proteins, enables detection and response to complex fluctuations within populations and surrounding environments. This robust function guarantees microbial self-preservation and ensures functionally interactive and dynamic communities. ❧ Information exchange between individuals and groups governs the growth, composition and behaviors of microbial ecosystems while affecting the speed of adaption and evolution. More specifically, the transfer of nucleic acids between cells through horizontal gene transfer (HGT) facilitates genetic plasticity and diversity in the microbial world. The unique ability of bacterial species to transfer DNA vertically and horizontally has led to the fast and continual evolution of the physiology and pathogenic character of bacterial species. ❧ More recently, research within the greater spectrum of bacterial communication, from protein signaling to gene transfer, has become increasingly invested in the role of extracellular vesicles (EVs) in a broad range of interactions. Originally seen as a random by-product of cell growth, EVs are now understood to be critical for many cellular processes. More specifically our work investigates the capacity of extracellular vesicles to mediate horizontal gene transfer between a broad range of bacterial species. Studies over the last century have proven the necessity and prevalence of horizontal gene transfer in the survival of bacterial populations living in different niche environments. While previous work has focused on three mechanisms of gene exchange, each with specific limitations, much less is known about the potential for this fourth mechanism, vesicle-mediated gene transfer, to contribute to gene flow patterns observed in microbial ecosystems. ❧ This dissertation explores the scope and capacity of gene exchange in bacterial extracellular vesicles. We will consider multiple properties in plasmid physiology and the role they play in EV production and packaging. The parameters that mediate and control vesicle- mediated DNA transfer will also be investigated. Together, we will identify multiple factors that can alter the loading of DNA into extracellular vesicles and the changes in genetic transfer rates