In an Ames test using his⁻ Salmonella bacteria a researcher deter...

Question

In an Ames test using his⁻ Salmonella bacteria a researcher determines that adding a test compound plus the S9 extract produces a large number of his⁺ revertants but mixing the strain plus the test compound without adding S9 does not produce an elevated number of his⁺ revertants.

What is the reason for the different experimental results described?

Accepted Answer

Hi, everybody. Here's our next problem. What is the purpose of adding S nine extract in an aims test choice A to directly cause genotoxic toxic effects in salmonella bacteria. Choice B to inhibit the toxic effects of the test. Compound. Choice C to simulate metabolic activation of the test compound or choice D to enhance the growth of salmonella bacteria. So let's just recall briefly. The purpose of the aims test. You have salmonella bacteria that have been mutated. So they are not able to synthesize histidine for themselves. So they can't grow in a medium that doesn't contain histamine. You then expose them to the test compound that you're trying to determine if it has muto GIC capabilities. If the compound is a mutagen, some of those bacterial colonies are going to be mutated back to the wild type. So if compound is a mutagen, some colonies will grow on those plates without histidine because they've been mutated back to the wild type. However, it's not sufficient just to expose them to a possible mugen because some Mutis only have this activity after being metabolically activated. So in going through a more complicated organism, they get processed by the body processed in the liver. And that processing is what activates them, turns them into a form where they cause the muto genetic damage. So, if we want to really test in the most accurate way possible, whether a compound can be a mutagen, we need to somehow simulate this metabolic activity because a salmonella bacteria doesn't have a liver. So, s nine extract is an extract of liver enzymes. We can recall from our content video. So its purpose is in as in choice C to simulate metabolic activation of the test compound. So to make sure again, we're kind of duplicating as much as possible, what might happen inside the body of a more complex organism. So choice C is our answer. We'll take a look at our other possibilities. Choice A to cause genotoxic effects, we wouldn't want that. We're testing our test compound to see what it does to the genes A choice B to inhibit the toxic effects. We don't want to do that either. And then choice D to enhance the growth of the bacteria. We don't need to do that. It will grow if it has a back mutation to the wild type and can make its own histidine. So that's why those answers aren't correct. The purpose of adding S nine extract. And the aims test is Choice C to simulate metabolic activation of the test compound. See you in the next video.

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