Bacterial Genetics: Transformation

Transformation is a genetic exchange mechanism by which “naked” DNA is taken up by bacteria.  This newly acquired DNA may include genes that enable bacteria to perform tasks that were previously impossible.  For example, a gene that enables the microorganism to digest oil spills or perhaps more simply, as seen in this experiment, to produce the Green Fluorescent Protein (GFP).  The gene coding for GFP comes from the bioluminescent jellyfish, Aequorea victoria, and resides on a DNA plasmid called pGLO.

The pGLO plasmid also contains a gene encoding for beta-lactamase.  Beta-lactamase is an enzyme that will allow transformed bacteria to be resistant to antibiotics that have a beta-lactam ring.  Thus, in order to identify bacteria that have been transformed with pGLO, we select for their growth using a media that contains an antibiotic with a beta-lactam ring, ampicillin.  The use of media containing ampicillin allows for the selection of successful transformants, however it is only when the sugar arabinose is also added to the media that it will be possible to observe the bright green fluorescence.  This is because the GFP protein is under the control of an arabinose operon.  Thus, arabinose acts like a switch turning on the section of DNA that codes for GFP.

Please refer also to the course web site for detailed lecture notes, which include explanatory pictures.

Rachel Watson, M.S.
AG 5010
766-3524
Cell: 307-760-2942
rwatson@uwyo.edu