Bacterial Transformation

in this video we're going to begin our lesson on bacterial transformation. A type of horizontal gene transfer. And so recall from our previous lesson videos once again that transformation is a type of horizontal gene transfer that's characterized by the uptake of free or naked D. N. A. In the environment by the cell. And so the cell is able to uptake free or naked D. N. A. From the environment. And that is called transformation. Now in order for a cell to transform D. N. A. It must be what is known as a competent sell. And a competent cell is really describing a really complex physiological state. And so um competent cells are really cells that have the ability to transform D. N. A. From the environment. To in other words uptake naked DNA from the environment. If a cell is not competent then it will not be able to transform DNA. And so if we take a look at our image down below notice that its distinguishing competent cells versus non competent cells. And so notice the cell that's over here on the left is a totally competent cell. And again competency is describing a really complex physiological state. But in the end competent cells have the ability to transform or uptake DNA from the environment. And so notice that this cell is able to transform naked DNA from the environment. And so this naked DNA is just this bear DNA. That you see here and it's able to transform it or uptake that naked DNA. So you can see the naked D. N. A. Is able to make its way into the cell because the cell is competent. However, a cell that is not competent like this one over here notice is not able to uptake D. N. A. It's not able to transform D. N. A. And so the D. N. A. Is not able to get into the cell if it's not competent and so only competent cells are capable of transformation. Now cells can actually be either naturally competent or cells can be induced to be competent by chemical treatment. And so some chemical treatments can induce cells to become more competent and allow them to transform or uptake external D. N. A. And so this year concludes our brief lesson or a brief intro to bacterial transformation and competent cells and we'll be able to learn more about transformation as we continue to move forward in our course. So I'll see you all in our next video.

in this video we're going to discuss the mechanism of natural transformation which is one of the types of horizontal gene transfer. And so cells that are naturally competent and able to transform or uptake D. N. A. Can regularly transform or uptake DNA from the environment when that D. N. A. Is available. And the reason that DNA might be available in the environment is because maybe a nearby cell lISZt or ruptured and released its D. N. A. Into the environment. And so natural transformation can really occur in a series of four steps that we have numbered down below 123 and four. And so what you'll notice is that in these images these blue structure here represents a bacterial cell. And on the inside this circular structure here represents the chromosome of the bacteria. The original DNA. That belongs to that bacteria. And then what you'll notice is that this little segment of DNA over here it represents the free naked DNA. That is going to be transformed by the cell or uptake into the cell. And so this free naked D. N. A. In many cases is going to contain genes and in this case it contains an antibiotic resistance genes for antibiotic X. Here and the X. Is just any antibiotic. And just for the sake of an example here. Okay and so here what you have is the antibiotic resistance gene found in this external piece of DNA. And so this external piece of DNA is a double stranded DNA molecule. And that's what the Ds here represents in front of the D. A. D. N. A. So the D. S in front of the D. N. A. D. S. D. N. A. Is just double stranded DNA. And so the double stranded DNA molecule and the free naked D. N. A. Is going to simply bind to cell surface receptors on the surface of the bacteria. Okay so it's going to bind and attach. And then of this double stranded DNA molecule only a single stranded piece is going to enter. And so the S. S. DNA that you see here represents a single stranded DNA. And so a single strand of DNA is going to enter the cell and uh the compliment strand, the other strand is going to get degraded. And so you can see here that one of the strands is going to be broken up and degraded. Whereas the other strand is actually going to enter the cell. And so the single strand of DNA that enters the cell is then going to integrate into the host cells chromosome. And it does this via homologous recombination. And so you can see this little single stranded piece of DNA that has entered has been transformed is going to integrate into the chromosome via homologous recombination. And so you can see the integration here and then in the fourth and final step here the cell is going to rebuild the compliment strand, the other strand that was degraded. And so it rebuilds that. So now we have a double stranded region back in place here. And so now this antibiotic resistance gene has now been incorporated into the chromosome. And so now the cell has resistance to antibiotic X. Because it obtained this antibiotic resistance gene through horizontal gene transfer through natural transformation. And so this year concludes our brief lesson on the mechanism of natural transformation, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

What does it mean when a bacterial cell is naturally competent?

• A. The bacterial cell is able to transform its chromosomal DNA into RNA.
• B. The bacterial cell is able to transform DNA from their environment.
• C. The bacterial cell is able to degrade viral DNA from attacking viruses.
• D. The bacterial cell is able to take in naked DNA and incorporate that DNA into its genome.
• E. A and C.
• F. B and D.

Bacterial cells can become competent in two ways, which are:

• A. Spontaneously.
• B. Instinctively.
• C. Horizontally.
• D. Induced.
• E. A and D.
• F. A and C.
• G. B and C.

DNA transformation in bacteria is an important tool for DNA modification and cloning experiments. If the DNA being transformed by the bacteria contains antibiotic resistance genes, how does this help the scientists?

• A. Antibiotics will kill any bacteria that did not naturally transform the transferred DNA.
• B. It allows the scientists to identify which bacterial cells are competent and which cells are not.
• C. It allows scientists to remove all bacteria that have not incorporated the experimental genes into their genome.
• D. All of the above are reasons why antibiotic resistance is commonly used in transformation experiments.