Enrichment Media - Video Tutorials & Practice Problems
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Enrichment Media
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in this video, we're going to begin our lesson on enrichment media. And so in order to isolate an organism that's present in really, really small amounts of a mixed sample, scientists generally use enrichment media. And so enrichment media is really just a special type of microbial growth media that is only going to have nutrients that are favorable for only a specific microbe. And so only that specific microbe is going to be promoted to grow, whereas the other microbes that are in that mixture are not really going to be promoted to grow as much. And so this helps to enrich that microbe that is present in small amounts. And so, enrichment media is really going to be similar to selective media because they both helped to promote the growth of a specific type of microbe. However, unlike selective media, enrichment media does not contain inhibitors. And so the enrichment media is not going to be inhibiting the growth of the others, it's only going to be promoting the growth of a very specific microbe. And so the enrichment media is specifically designed to promote the growth of an undetectable level of microbe that's found in really really small amounts uh to a detectable level of that microbe that's found in larger amounts. So it's really just helping to enrich a very specific microbe that is found in small amounts. And so if we take a look at this image down below, we can get a better understanding of enrichment media. So notice over here on the far left, what we have is an original culture, a liquid culture inside of a test tube that is going to contain a mixed culture of microbes that has a bunch of uh a big mixture of many different types of microbes. Um And even the species of interest is going to be present in this mixed culture. However, the species of interest is going to be found in really really small or low levels and so it is present in there but there's not that many of them. And so what the scientists can do is transfer the original culture uh to an enrichment media. And that's what's over here in this test tube is the enrichment media. And so the enrichment media is once again going to contain only nutrients that are favorable for only a specific microbe. And so only that specific microbe is going to be promoted to grow. And so the species of interest is going to grow and grow and number. And the other species that are in there are not really going to be promoted to grow and so they don't really grow as much. And so the species of interest has been enriched, It has increased uh in its population size. And so the enrichment media can then be transferred over to a solid auger plate. Like for example a chemically defined media plate where the composition of the nutrients is exactly known to the scientist. And so the scientists may choose to have nutrients that are only going to be beneficial and favorable for the species of interest to help promote the growth of that species of interest even more. And so the only colonies that are going to arise on this chemically defined media are the ones that were enriched from the enrichment media. So it's only going to be the ones that are the species of interests. So the inch and rich culture is going to be plated and the species of interest can easily be isolated from this plate just by picking one of these colonies. And so this year concludes our brief lesson on enrichment media and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video
2
Problem
Problem
Microbiologists can use a range of media to grow microbes in the lab. If a microbiologist wants to differentiate hemolytic bacteria from non-hemolytic bacteria in their sample, what form of media should they use?
A
Selective media.
B
Complex media.
C
Differential media.
D
Chemically defined media.
3
Problem
Problem
A microbiologist takes a water sample from a lake and the sample has a variety of bacterial species. However, she only wants to grow one species of bacteria from the sample for her experiment. What form of growth media should she use in her experiment?
A
The scientist should use an enrichment medium that only supports the growth of the species she is interested in.
B
The scientist should use a differential medium to differentiate the different species in her sample.
C
The scientist should use a reducing medium to only grow anaerobic species.
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