In this video, we're going to begin our introduction to bacterial plasmids. And so plasmids are really just small molecules of circular double-stranded DNA that can be replicated independently of the cell's chromosome. Now these plasmids, they typically contain genes that are not required for survival of the cell. And so if the cell loses a plasmid, in many cases the cell will still be able to survive. Now that being said, some plasmids do have genes that provide key features for survival. For example, antibiotic resistance. But for the most part, plasmids do not have genes required for survival. Now the plasmids are to be replicated by the cell's DNA polymerase, which is the enzyme that performs DNA replication. Now curing is actually a process where the cell loses its plasmid. And when the cell loses its plasmid, this can actually be something that happens spontaneously or naturally, or it's something that can be induced chemically by a scientist. And so if we take a look at our image down below, we can get a better understanding of plasmid curing with chemical induction. And so notice on the left-hand side over here, we're showing you a bacterial cell, and notice that the bacterial cell has its own chromosomal DNA here in red. But notice that over here in green, there's a circular, a small circular double-stranded DNA molecule that we call a plasmid. And once again, this plasmid does not typically contain genes that are required for survival. And so through plasmid curing, which can be induced chemically, chemical induction will allow the cell to lose its plasmid. And so you can see that the plasmid is being lost here. It's being removed. And so over here, we have the cell, which no longer has that plasmid. And notice the cell is saying, "that's okay. I don't really need it." And so once again, in most cases, these plasmids do not have genes that are required for survival. However, in some scenarios, they can have genes that provide key features such as antibiotic resistance. But for now, this here concludes our brief introduction to bacterial plasmids, and we'll be able to apply these concepts here as we move forward. So I'll see you all in our next video.
Introduction to Bacterial Plasmids - Online Tutor, Practice Problems & Exam Prep
Introduction to Bacterial Plasmids
Video transcript
Which of these is NOT true regarding bacterial plasmids?
Which types of genes are commonly found in bacterial plasmids?
Episomes
Video transcript
This video, we're going to introduce episomes. An episome is really just a special type of plasmid that has the unique ability to integrate into the bacterial cell's chromosome. This integrated DNA is actually going to be replicated along with the bacterial chromosomal DNA. It can be inherited by the daughter cells in this fashion. If we take a look at our image down below, we can examine how episomes are plasmids that can integrate into a bacterial chromosome. Notice over here on the far left, what we're showing you is a bacterial cell. You can see the bacterial chromosome is here in red. Over here in green, what we have is this specialized plasmid called the episome, which has the ability to integrate. Notice that through integration, the episome is now embedded within the chromosomal DNA. We have our integrated episome here. Now that the episome has been integrated, it will be replicated along with the bacterial chromosome itself. Through binary fission, the two daughter cells that result are each going to have a copy of the bacterial chromosome with the episome integrated into that position. This here concludes our brief introduction to episomes, 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.
Episomes differ from normal bacterial plasmids because…
Some bacterial viruses (lysogenic phages) carry viral DNA that acts like an episome. When a bacterial cell that is infected by a lysogenic phage replicates, what happens to the viral DNA?