Question

Explain why pGLO transformed E.coli DOES NOT exhibit fluorescence under UV when grown in LB/AMP plates?

Answer 1

pGLO plasmid contains several elements critical to its function:

1) GFP gene, which confers green fluorescence in the presence of UV light when the gene is expressed.

2) bla gene, whose gene product confers ampicillin resistance to bacteria when it is expressed.

3) araC gene, a component of the arabinose operon whose encoded protein stimulates GFP gene expression from the PBAD promoter when arabinose is present.

After E. coli transformation, the cells that have been transformed with pGLO DNA is accomplished by growth on ampicillin containing plates. When pGLO transformed E. coli cells are grown in nutrient medium containing arabinose as well, GFP expression is stimulated and the bacteria will glow brilliant green upon exposure to UV light. The GFP gene remains turned off and the colonies appear white when arabinose is absent from the nutrient medium. This is why pGLO transformed E.coli does not exhibit fluorescence under UV when grown in LB/AMP plates.