Date of Award

Spring 2009

Document Type



Life & Environmental Sciences


Plasmids carry highly specific antibiotic resistance genes and are well known to influence processes involved with bacterial cell reproduction, conjugation, and proliferation. These factors that cause horizontal gene transfer are significant in understanding bacterial communication and possible limits in health care, such as improved antibiotics. Previous work by De Gelder et Al., 2008 indicated one specific mutation in a gene that provides an important protein in the formation of the conjugation pillus, trbC altered the stability of plasmid pBlO—a plasmid well known to be a broad host range plasmid that mediates several antibiotic resistance factors. My research focused on the molecular mechanism involved with this increased stability of plasmid pBlO by investigating whether a possible improvement in transfer efficiency could explain the signature response in unstable hosts such as Stenotrophomonas maltophilia. Through a process known as liquid mating, transconjugants were formed with ancestral plasmids, pBlO and evolved plasmids, pSH3 and pSH5. The donors, recipients and transconjugants were then plated onto limiting media, and counted in triplicate. Results suggest an increased plasmid transfer rate with both evolved plasmids pSH3 and pSH5 compared to ancestral plasmid pBlO.