Date of Award

Summer 2005

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Wayne L. Hynes

Committee Member

Robert Ratzlaff

Committee Member

Christopher Osgood

Call Number for Print

Special Collections LD4331.B46 L47 2005


Green fluorescent protein (GFP) was first identified in the jellyfish Aequorea victoria and generated interest due to its ability to noninvasively tag and visualize cells, cellular structures, and cellular proteins. Furthermore, the expression of green fluorescent protein in Esherichia coli cells as a tool for reporting gene expression and promotor activity has become important in the understanding of gene regulation. Expression of the gfp gene was found to vary depending on the strain of E. coli possessing the gfp gene. As a result of this fluctuation in fluorescence, gene expression and hence promotor activity may be difficult to detect or even overlooked. In this study, the fluorescence of GFP in twelve E. coli strains used for reporting gene expression and promotor activity was investigated. Results indicated high variability of GFP fluorescence levels amongst the E. coli strains tested. Furthermore, a direct relationship exists between plasmid copy number and the fluorescence intensity displayed by a strain of E. coli. When conducting promotor activity and gene expression studies in E. coli with the reporter GFP, expression studies should be conducted to ensure that the strain being used has the ability to highly express GFP.


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