What indicates that a GFP-expressing colony has successfully integrated the GFP gene?

The presence of fluorescence under UV light is a definitive indicator that a colony has successfully integrated the GFP gene. Green Fluorescent Protein (GFP) emits a bright green fluorescence when exposed to UV light, resulting from the expression of the introduced GFP gene. This fluorescence is a direct result of the successful transcription and translation of the GFP gene, confirming that the cellular machinery is functioning properly with the integrated genetic material.

In contrast, immediate changes in broth color might occur due to other factors unrelated to GFP integration, such as changes in pH or nutrient levels. Unique colony morphology on the agar plate could suggest some level of genetic alteration, but it is not specific to the presence of the GFP gene. Similarly, increased growth rates could be influenced by various environmental or genetic changes that are not necessarily linked to the successful expression of GFP. Therefore, fluorescence under UV light serves as a clear and specific assay for confirming the successful integration of the GFP gene into the bacterial colony.