Last week, AP Biology students explored genetic engineering by transforming a regular (wild type, non-virulent) strain of Escherichia coli (E. Coli) with a plasmid. A plasmid is a small, lab-created piece of circular DNA that has specific genes on it. The students gathered the results of their bacterial transformation lab and discovered glowing results.
The gene they inserted is called GFP (or pGLO) and it’s found in nature in jellyfish. It allows the jellyfish to glow in UV light, and it works the same way when inserted into bacteria.
The students collaborated in pairs to learn not only about transformation but also about experimental design technique. The procedure involves keeping the bacteria on ice for most of the experiment but doing a fast (50-second) heat shock at 40 degrees Celsius. “That sort of opens up the pores of the bacteria and can allow a plasmid to slip in,” explains Laura Bradford, Upper School Science Teacher. “The genes on the plasmid we inserted include a gene for ampicillin resistance and a gene for GFP.” The heat shock method is a standard technique used in many research and biomanufacturing laboratories. Bacteria transformed with the pGLO plasmid are selected by ampicillin resistance, which means they will be the only bacteria to grow on a petri dish that has ampicillin on it. Ampicillin normally kills regular or wild-type bacteria. When induced to express GFP, the bacteria glow fluorescent green under UV light!
The exercise also helps illustrate the Central Dogma of Genetics, that DNA can come from any source (like a jellyfish) and still be expressed into the exact same protein in a bacteria.
After conducting the experiment, students took their Petri dishes downstairs in the STEM building, to a room they could make completely dark. They used UV lights to observe their results and discovered an eerie, green glow.
“This experiment was compelling because of the contemporary molecular techniques we used to transform our bacteria to express a bioluminescent protein and then regulate its expression using external factors,” said Owen Limbrick ’23. “I found the lab particularly captivating because of the access our class had to many of the same technologies that are currently being used in medicine and across the bioengineering industry.”