Prokaryote Lineages - Video Tutorials & Practice Problems
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Prokaryote Lineages 1
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Hi. In this video, we're going to take a quick tour of some of the major lineages of prokaryotes. We're going to begin with proteobacteria, a diverse clade of gram negative bacteria that's actually organized into 5 subgroups that are named with Greek letters alpha, beta, gamma, delta, and epsilon. And you can see a phylogenetic tree of proteobacteria right here. Now you might notice that this also includes zeta proteobacteria. This is a newer grouping and your books likely won't include it. Now, many, species of proteobacteria are involved in nitrogen fixation don't forget that it was proteobacteria that don't forget that it was proteobacteria that was engulfed by a cell and eventually would become mitochondria. So and of course they led to a super important structure in eukaryotes. Now moving on, we have chlamydia which is a group of gram negative bacteria that lack peptidoglycan in their cell walls. Hopefully remember that, gram negative bacteria usually have a thin layer of peptidoglycan, below the outer, lipopolysaccharide layer. Well, these bacteria actually don't have that peptidoglycan at all. They're also all parasites. All of the species in this group are parasites that live inside host cells and you can see a picture of that happening right here. These translucent blobs are those host cells and you can see these 3 have these brown spots inside them. Those brown spots are the chlamydia cells that have been stained with a particular stain turning them brown so that we can visualize them. Those cells have been infected with chlamydia. The chlamydia is living inside of them. Again, if this name sounds familiar, it's because, the famous STD chlamydia is, caused by a bacteria caused by bacteria in this group. We often just refer to it as chlamydia though, the sort of, group name. Now, spirochetes are gram negative heterotrophs and what's, distinct about them is their corkscrew shape that you can see in these two pictures. This sort of zoomed out one, those little dark squiggles, the these cells that are stained in yellow in this image. And for a more zoomed in look, some an image of a spirochete, much more zoomed in. You can really see that corkscrew shape in the bacteria. Spirochetes actually there are 2 famous diseases caused by spirochetes that you've probably heard of. Those are Lyme disease and the STD syphilis. Lovely things spirochetes, right? Lovely diseases. All right. With that, let's and I'm sorry. I'm just making a joke. I'm being sarcastic. Don't mean to make light of diseases caused by these bacteria. But yeah. Basically, the endpoint is nasty little guys, these spirochetes. Alright. With that, let's turn the page to talk about some other bacteria.
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Prokaryote Lineages 2
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Cyanobacteria are gram negative photoautotrophs, and many species actually perform nitrogen fixation. Now they are sometimes termed blue green algae, but this is a bit of a misnomer, as they are in fact prokaryotes, not eukaryotes at all. They're actually the only bacteria that perform oxygenic photosynthesis, and it's pretty incredible because they're responsible for the origin of oxygen in the atmosphere. And you can see a nice up close image of some cyanobacteria here. These are, cyanobacteria that grow in filaments. Some grow as like free floating little cells and others form colonies. And you can see that, this is a satellite photo here. And this green mass here, that is just cyanobacteria. That is a huge bloom of cyanobacteria, you know, obviously generating a bunch of oxygen because it's performing a bunch of photosynthesis. I mean, pretty amazing. This is a satellite photo and there is so much of these tiny microorganisms. There's, or rather, there's so many of these tiny microorganisms that we can see it from space. And actually the oldest fossils we have of life on earth come from cyanobacteria. These are stromatolites. These, blobs of what look like rock, it's actually calcium carbonate, and, this is exuded by certain types of cyanobacteria. And, basically, the oldest fossils we have of life on earth are stromatolites from cyanobacteria. These are modern, you know, living cyanobacteria, but we have stromatolites that look like these from, you know, over a 1000000000 years ago. It's amazing. Now, and and also, don't forget, lastly, that cyanobacteria are the organisms that were engulfed and eventually became chloroplasts. Now, actinobacteria are high GC gram positive bacteria. And what that means is is they have a large, or a high percentage of guanine cytosine, right, GC from DNA in their, chromosome. So they have a high GC content, so to speak. They're gram positive bacteria and they include the genus Streptomyces, which is responsible for many antibiotics. Many antibiotics have come from this genus of actinobacteria. Now, these were initially misclassified as fungi fungi because they have a fungus like morphology. And as you'll see in the name, it ends with myces. What you'll see once we or when we discuss fungi is that, the names, the Latin names for fungi end in myc's. So these were initially thought to be fungi, actually, bacteria. Now, the misclassification comes from the fact that chains of cells form these branching mycelia. And it's these structures that caused, biologists to think that these were actually fungi. Lastly, we have the Firmicutes, which are low GC gram positive bacteria. So, the high GC is basically in comparison to these low GC bacteria. The high GC is basically in comparison to these low GC bacteria. And this actually includes, this group includes the genus Lactobacillus, which is super important to humans. Not only are they responsible for yogurt production, obviously very important, and, also they're involved in cheese production, very important. And most important to me, they're involved in sour beer production. If you've never heard of sour beer, you should try it. It's delicious. And it involves, fermentation with lactobacillus inside humans that are super important, for inside humans that are super important, for our health. I mean, many species live in our gut and help us with digestion. There are species that live in the vagina that help maintain that environment, and that's actually what this image is from. This is a human cell and you can see, this is a human cell and you can see all these little dark rods. Those are lactobacillus, and they are a species of lactobacillus that live in the vagina. Alright. That's it.