Fifteen bacterial colonies growing on a complete medium are tr...

Question

Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.

The three colonies that do not grow on minimal medium are transferred to minimal medium supplemented with the amino acid serine (min + Ser), and all three colonies grow. Characterize these three colonies.

Accepted Answer

Hello, everyone. Welcome back. Let's look at our next question. It says in genetic engineering, oxo trophic bacteria can be used as selectable markers. Which of the following is an advantage of utilizing oxo trophic bacteria in this way. Well, we'll get to our answer choices and go through them. But first, let's just recall what oxo trophic bacteria are and how they get used as selectable markers. So we can recall from our content vid videos that these are bacteria that have mutations that make them unable to synthesize an essential nutrient. So you therefore can select four bacteria that have acquired the gene by give, by growing them on media lacking the nutrient. So you can start with an oxo bacterial line that lacks the ability to synthesize a certain nutrient. Then add in DNA by various methods, whether you're transforming them or conjugating them and use a marker as a marker. A gene that allows them to synthesize that nutrient. Again, you can check whether or not you've transferred that DNA and you can attach other genes to it by whether they can grow in media that's missing this essential nutrient. So it makes them selectable markers So with that in mind, let's look at our answer choices and figure out which one is an advantage of using oxo trophic bacteria as selectable markers. Choice A says they are quickly destroyed by antibiotics. Well, a lot of times antibiotics are used um as part of a selection process. If you have a gene that conveys resistance to an antibiotic, you can then use that antibiotic to select for bacteria with that. But that's not using oxo bacteria. So choice A is not an advantage of these particular bacteria. Choice B is they are easy to genetically manipulate. And this is correct. And that's because these genes that govern the production of the essential nutrient are actually easily discovered and modified. So it makes it very easy to fiddle with them, create genes that either lack or have the ability to synthesize the nutrient. And then you can use that to select for bacteria that have or don't. So this is definitely an advantage of using them. So I'm going to mark this with a little dot As most likely my correct answer, but just wait and see what the other answers are. Make sure this is the best one choi says they are resistant to environmental stresses. Well, again, there are strains of bacteria that can withstand certain environmental stresses and you might use those stresses like high heat to select for them. But that's not what's going on with oxo bacteria. So it's not a correct answer. And finally choice D they are highly pathogenic meaning causing disease. Well, no, that's not why you use them. So choice D is not our correct answer. So having eliminated our other three, we can definitely pick choice B as the answer here. So what is the advantage of utilizing oxo trophic bacteria, selectable markers and its choice B they are easy to genetically manipulate. See you in the next video.

Key Concepts

Minimal Medium

Amino Acid Supplementation

Auxotrophy

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