Put the following substances in the order they are used in a G...

Question

Put the following substances in the order they are used in a Gram stain: counterstain, decolorizing agent, mordant, primary stain.

Accepted Answer

Welcome back, everyone. Let's look at our next question. In a microbiology lab, you are tasked with performing a gram stain on a bacterial stample, which of the following represents the correct order in which you would use these substances. Mordant counter stain, primary stain and decolorize agent. And then our four answer choices represent these in different orders. So let's think about what we need to do when performing a gram stain. So we're going to have our initial violet color stain done by the dye crystal violet. So that would be logically a primary stain and this will stain all of our bacteria, gram positive and gram negative a deep purple color. Well, if I'm on the test and time is of the essence here, I'm going to go ahead and check my answer choices right away. And in fact, I'll find out that only one of them. Choice B has primary steam first. So I can automatically eliminate AC and D A has mordant first, C has counter steam first and D has decolorize agent first. So again, if I'm doing this in a time scenario, there I go. Choice B is my answer. I don't have to do anything further. But this is a tutorial video, we're supposed to be kind of learning from it. So in the interest of being through, let's walk through our other steps, which we now know the order. So the second step, we don't often think of when we think about Graham standing, we might not even remember it's there, but that's number two, which is a mordant and this is iodine and it reacts with the crystal violet to create an insoluble complex. And so now we've got these, this insoluble precipitate in the cells that you've stained. So it just makes it so that it's sort of fixed in there rather than just all washing away in the next step. Now, we probably remember the next step, which is that we're going to add the decolorize agent, which is going to decolorize the gram negative bacteria but not the gram positive bacteria. And thus, we get our terms gram positive and gram negative and that the gram positive bacteria are positive for that primary stain. It remains there and they show that color the gram negative bacteria, that primary stain gets washed away. And this is because the gram negative bacteria, although they have a cell wall, it's um it's easily degraded by this acetone alcohol solution. So it kind of degrades the cell wall and then they just have this thin peptidoglycan layer underneath. So it very easily kind of breaks down and then you wash away that purple color. Well, you don't really want to stop there because now you have purple stained gram positive bacteria, but gram negative bacteria can no longer be seen under a microscope because they've become decolorized. And so finally, you use your counter stain generally Safran, which is a red stain. And now you end up with your gram negative bacteria appearing pink due to being stained by the sorain, that sorain can stain the gram positive bacteria as well, but they're already a deep purple color. So you won't really see that pink color from the Soran. So we can see that in choice B we do have this correct order uh of all the the substances. Our answer for doing a gram stain and the order in which you use the substances is choice B primary stain, mordant, decolorize agent and counter stain. See you in the next video.

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Put the following substances in the order they are used in a Gram stain: counterstain, decolorizing agent, mordant, primary stain.

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