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Microbial Factories: Using Bacteria to Make Specific Compounds

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  • 0:07 Vitamin Supplements
  • 1:13 Microbial Factories
  • 3:45 Microbial Factory Hosts
  • 5:01 Plasmids
  • 6:02 Current Microbial…
  • 6:50 Lesson Summary
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Lesson Transcript
Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

Microbial factories make use of microorganisms to produce commercial products. In this lesson, we will examine the advantages to using microbes and look at a few commonly produced compounds.

Vitamin Supplements

It shouldn't be a surprise to learn that the cells in living organisms have to make or consume everything they need to survive. Since you evolved to need vitamin B12, you can rest assured that it must be getting produced somewhere. But not by you, your salad greens, or the beef in your steak. Nope, vitamin B12 is only produced by a few species of bacteria and archaea. That means that you have to eat these microbes or, better yet, just have a few living in your gut, if you want a healthy, vitamin B12-enhanced nervous system.

Then again, you could simply go buy vitamin B12 supplements and end your dependence on microbes. The problem with vitamin B12, though, is it's a large and complex molecule. Take a look at this beast:

Structure of vitamin B12
structure of vitamin b 12

Synthesizing a molecule with such bulk step by step can be time-consuming and expensive. Wouldn't it be nice if we could get those bacteria and archaea to do it for us? They've already evolved an efficient production process. All we have to do is harvest the finished product. In fact, that is exactly what happens.

Microbial Factories

We'll come back to vitamin B12 in a minute. First, let's discuss the concept of a microbial factory. We know what microbes are: tiny organisms including bacteria, archaea, fungi, and protozoa. We know what a factory is: a building where products are made. So, it follows that a microbial factory is using a microbe to make a product. In this case, the factory building is the microbial cell! And, the products we're referring to include antibiotics, vitamins, hormones, proteins, vaccines, enzymes, and countless other small, organic compounds. The potential products are almost limitless. And so are the advantages of using microbes.

Let's look at vitamin B12 again, seen above. This molecule is large with a very complex and specific structure. Change the placement of one atom or bond, and you destroy the functionality of the vitamin. In order to chemically produce vitamin B12, you would have to figure out every step individually, place them in a very specific order, and make sure you can purify the vitamin B12 out of all the chemical catalysts you added and away from all the unwanted byproducts. And some of those catalysts are invariably toxic, reactive, heavy metal compounds that you really don't want tagging along in your daily multivitamin.

The bacterium Pseudomonas denitrificans, our microbial factory, has already taken care of all these issues. This bacterium already knows how to make vitamin B12, without making any errors in the final structure. There are no toxic byproducts because that would harm the bacteria. There are no industrial strong acids or bases, solvents, or heavy metals required because these would have to be produced by the bacterium and would likely end up harming it. All we're left with is the most efficiently produced vitamin B12 the Pseudomonas is capable of.

But that's not the end. Ever hear of genetic engineering? If not, there is a great lesson entitled What is Genetic Engineering? you might want to watch. Simply put, genetic engineering is the process by which scientists modify the genome of an organism. Through genetic engineering, we can modify the genome of our Pseudomonas so it makes very large amounts of vitamin B12, often up to 20,000 times more than normal, or secretes the B12 out of the cell so it is easier to collect. You can see how using the bacteria to make the vitamin can make a very tedious process much easier, safer, more efficient, and, the magic word, cheaper.

Microbial Factory Hosts

This example of vitamin B12 is actually very straightforward. We found a safe bacterial species that already makes our desired product and exploited it. But it rarely works out that well. Not every bacterium produces the things we want; some even produce very deadly byproducts and toxins we definitely don't want. To top it off, there are some compounds that higher organisms, like humans, produce that bacteria don't. We need a way to customize our factory to make exactly what we need, make it correctly, and make it safe for human use.

The first step is to pick a host for our product. The host should be very well understood, easy to use, safe, and easily genetically modified. Possibly the two most studied organisms in history are the bacterium Escherichia coli and the yeast Saccharomyces cerevisiae. The vast majority of microbial factories are based on one of these two workhorses. They fit every criteria. Most strains are harmless to humans (excluding a few nasty food poisoning E. coli), they are easy to grow and grow very fast in a lab. Finally, and maybe most importantly, they are so well understood that genetic engineering with these two has become commonplace, predictable, and very successful.

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