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Glowing bacteria

Green Fluorescent protein (GFP) is a protein that glows under ultraviolet lighting. The gene encoding the green fluorescent protein is first isolated from a jellyfish and is used in biology as a reporter for gene expressions in organisms. Bacterial transformation is when DNA is passed between two bacterias through plasmids (DNA in bacteria). Here is what a pGLO plasmid looks like:

The ori is the origin of replication or where the plasmid DNA begins to copy itself. The araC is a DNA binding protein. When arabinose sugar is present, it interacts with the araC allowing the RNA polymerase (an enzyme that is responsible for copying a DNA sequence into an RNA sequence during transcription) bind and the GFP will be expressed. However, when arabinose sugar is not present the GFP will not be expressed. The bla is a gene that codes for beta lactamase (an enzyme that allows the antibiotic ampicillin to be broken down), therefore the bla gives the plasmid ampicillin resistance. This means that only the bacteria that picks up this plasmid will have ampicillin resistance along with the other features this plasmid includes.

The way that scientist get bacteria to pick up these plasmid is through three basic steps:

  1. Add the Bacteria to Ice

  2. Add a transforming liquid which will loosen up the bacteria's membrane and this will make it more likely for the bacteria to pick up the plasmid.

  3. Heat shock the bacteria which will cause some of the bacteria to pick up the plasmid.

In this particular lab there are several plates that have various combinations of arabinose, ampicillin, and more. Here are what the plates look like and I will explain them below the picture:

The top left plate is on LB and the bacteria did not pick up the plasmid. The bacteria in this plate is able to grow as there is no ampicillin (amp, the antibiotic). So they are able to grow even though they do not have that cool feature from the pGLO of being ampicillen resistant. However, as there is no arabinose sugar present, there will be no expression of the GFP or no glowing.

The top right plate is on LB and ampicillin, and the bacteria still has not picked up the plasmid. The antibiotic in this plate is present, however the bacteria did not pick up the plasmid so it does not have the ampicillen resistance feature. Because of this, the bacteria is unable to grow.

The bottom left plate is on LB, ampicillen, and the bacteria did pick up the plasmid. Even though ampicillen is present, because the bacteria picked up the plasmid it has the ampicillen resistance feature. The bacteria will be able to grow in colonies. However, arabinose sugar is not present so there will be no glowing on that plate.

The bottom right plate is on LB, ampicillen, arabinose sugar is present, and the bacteria picked up the plasmid. This is similar to the bottom left plate. The bacteria will grow as it has ampicillen resistance. However, this plate also has arabinose sugar meaning that the GFP will be expressed which is why that plate is the only plate that glew.

To learn more click below:

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