18. Viruses, Viroids, & Prions
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in this video we're going to introduce plaque assays. And so since bacteria pages or fe ages are obligate intracellular parasites that cannot replicate outside of a host cell cultivation of the appropriate cells is actually required for studying these fage is and so plaque essay is a specific laboratory technique or method that is used to determine the concentration of fage particles in a sample by the formation of plaques. Now, plaques are defined as clear areas in a layer of cultured cells that indicates cell death from fage infections. And so each plaque that's present represents a plaque forming unit or a P. F. U. For short. And so each platform ng unit or each PF U. Represents a single fage particle. And so the number of plaques can be used to represent the number of fage particles. Now dilution of the fage sample are going to be used to control the number of pF us on the plate in order to determine the tighter and so the tighter is really just the concentration of fage particles in the original sample or in other words in the un or non diluted sample. And so if we take a look at our image down below, we can get a better understanding of these plaque assays. And so the plaque assays once again are going to be used to determine the tighter or the concentration of bacteria pages and so notice on the far left over here, we have the first step where we have a lawn of bacteria growing on a Petri dish. And so there are bacteria growing all over this Petri dish. And so then what we do is we introduce the bacteria fage, which is going to infect the bacteria. And so we introduced the bacteria fage and you can see here the fage is able to carry out a fage infection and the infected bacteria we know ultimately with the lyrics cycle is going to end up killing or licensing the cells. And so the infected bacteria are ultimately going to lice and die. And when they die, they create these plaques which are again, these clear areas that represent cell death. And so if you take a look at our image down right here, notice that there is a plaque forming right here, which is basically a cleared out area that does not have cell growth because the cells have died from the fage infection. And so this here would represent the formation of a plaque and so zooming into this region. This little zone here that has cell death is going to represent the plaque and so it's going to have infected bacteria that have LISZT. And so these infected bacteria LISZT and so they create these plaques. Now, ultimately the number of plaques when there are multiple plaques that form each plaque that forms represents a plaque forming unit or a P. F. U. For short. So one plaque represents one pf you and each pf you or each platform ng unit represents one fage. And so the number of plaques can be used to represent the number of fage is, and so it can be determined. It can be used to determine the tighter or the concentration of fage particles in the original sample. And so what you'll notice here is that through the formation of multiple plaques, as you see here, the number of plaques can be used to determine the number of pages and the tighter of the sample. And so this year concludes our brief introduction to plaque assays and we'll be able to get a little bit of practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
A clear area against a confluent "lawn"of bacteria is called a:
The approximate viral concentration of a sample is known as:
The lysate assay.
Which of the following statements accurately describes viral plaques?
Each plaque is presumed to arise form a single lytic virus particle.
Plaques are formed only by defective viral particles.
All bacteriophages produce plaques that have exactly the same size and appearance.
Plaques are only formed by animal viruses.e) Two or more of the above answers are correct.
Two or more of the above answers are correct.