Chapter 5 in your OpenStax textbook really covers what I personally consider some of the most interesting information that we get to cover in the microbiology class. This chapter focuses on the microscopic eucalyptus. They are a very diverse group, incredibly interesting. They are very complex in some of the ways that they can cause diseases. So this is just really one of my favorite topics.
for us to cover. The way this textbook sort of chooses to separate the different eukaryotic groups we need to discuss is into different supergroups. So I've gone through and I've used this terminology to help us separate out some things, but what is really most important as we go through is that you have a good understanding of how the different groups are similar to each other, how they're different.
what they can do for us that may be beneficial and then really what's usually most interesting for most students is what can they do for us that causes disease and that's generally what as a group of students you like to learn So just jumping right in, we're going to look at our first group. The first group we're going to look at are called protozoa. Protozoa are eukaryotes. They are all unicellular, meaning that every single protozoa... on Earth is going to be a single cell.
So they have that in common with bacteria, but they are eukaryotes. They have a nucleus, they have complex membrane-bound organelles. Not all protozoa are bad for us protozoa can be free-living or parasitic they can live in a variety of different environments one characteristic that makes protozoa interesting as well as harmful for those that do cause diseases is their ability to insist so when we have an active feeding protozoan it's going to be in the stage that we consider the trophozoite stage this is the stage where if it's a free-living protozoan, it's going to eat, do normal metabolic activities. If this is a parasitic protozoan, the trophozoite stage is going to be the stage where it's inside of its host, typically causing some sort of damage. So if it's in its active trophozoite stage, and then we have something that is bad for the protozoan, maybe the temperature is bad, it runs.
out of food something of that nature the trophozoite has the ability to insist so it forms a cyst this is not the same cyst you may have heard heard someone have a cyst on their ovaries or a cyst of that nature in the body this is actually just more like an endospore for bacteria it's the living organism is inside of this hard outer shell that's just allowing it to survive in the cyst staying the protozoan can live for very very long times until the environment gets better and then the cysts can go through an X-cystment where the trophozoite just burst back out and we have the active living stage again The reproductive cycles of protozoa can be anything from a simple binary fission, which is very similar to mitosis, or it can be something as complicated as sizogony. That's this word here. So sizogony is going to be where you have multiple replications of the nucleus, and so at one time, and then that one cell is going to burst and become many, many cells at once. If we look at the anatomy of this picture here at the bottom of your slide, which is kind of the generic picture of the protozoa, there's going to be a couple parts you need to be familiar with. So, of course, they'll have a plasma membrane.
They're a eukaryotic cell. That's called the plasma lemma. Sometimes a protozoa will have what's called a pelicle.
This is just an extra rigid protein coating on the outside of the plasma membrane. It just serves a protective function. Thank you. The inside of the protozoan is separated into two regions. The outermost region is very jelly-like.
It's called the ectoplasm. The ectoplasm is going to be where your movement structures are going to be incorporated. The endoplasm is the inside portion. It's a little more fluid-like.
That's where all the organelles will be located. With our protozoa, we are going to classify these. particular group by how they move. So we're going to see there's different movement structures that can be part of this ectoplasm. In this generic example the ectoplasm movement structure we see is labeled here the pseudopod.
Just a couple other little parts to finish up this picture. Of course we'll see a nucleus. This contractile vacuole is used for feeding purposes and then we'll see a few other things.
Food vacuole, storage of food, things of that nature. So looking at a few more structures, as I said, here's the next bullet. Protozoa are classified by how they move.
The three options for movement for a protozoa would be a flagella, shown in this picture. here, whip-like tail, cilia, which is multiple hair-like structures that allow the organism to move, or pseudopods, which are blunt-like extensions of the ectoplasm that can grow. So one portion of the pseudopod may extend out, grab a surface, pull, retract back, so it almost moves like slime if you think of it in that way. Just a couple other specialized structures to mention not in great detail but very interesting some of the protozoa will have a cytosol like we see here in the ciliated protozoa the cytosol is a mouth so the cilia will move and create a current causing food to go into the cytosol the food is then broken down by a digestive type system and then waste is put into the cytopropt so that it can be excreted by exocytosis so So between these two things and a few other parts within, we actually can see a almost rudimentary digestive system within this ciliate. And then the last one, that contractile vacuole, it helps with feeding, it's moving water and nutrients inside, in and out of the cell.
So let's get to some of the interesting stuff. Let's look at some of the disease causing protozoa. So we're in the first group of pseudopods, the first group of protozoa called the amoebazoa. All amoebazoa are going to move through the use of a pseudopod.
And there's two that I wanted to kind of go over with you that I thought you might find interesting. The first is Entamoeba histolytica. And so that's this term here.
Entamoeba is the gene that causes the development of the cell. genus of a group of protozoa that infect humans through ingestion of contaminated food and water. So this life cycle shown here shows you what's going on with the entamoeba. If you ingest food or water that is contaminated with the entamoeba cyst, that cyst will then move through your digestive tract.
Once inside of your intestine, then excistment will occur. So the cyst will mature. into an active trophozoite.
That protozoan then continues to multiply inside of your intestines. It can make you feel sick to your stomach. It can also, if you keep this infection long enough, that protozoan can move through your bloodstream to other areas and really cause some devastating disease. Since this protozoan is living in the intestine, it's very easy for it to be transmitted to complete its life cycle. If it's in your intestines, then some of them can actually leave out through feces, become cysts, and then if the situation's right for the protozoan, that cyst can then become part of new contaminated food or water and infect someone else.
The other one that I thought you might find interesting that belongs to the amoeba zoa group is called Nagleria Fowleri. This is the brain-eating amoeba that you've seen in the news quite a bit lately. So the way this amoeba... infects is when you swim in contaminated water, the amoeba can actually penetrate directly through your nasal mucosa. So it only has to have the ability for water to get into your nose.
I don't know about you, but when I when I go swimming, if I'm under water, water is going to get in my nose. And so once inside of your nasal cavity, that amoeba can infect your brain directly, feeding on your brain cells. Very, very nasty infection.
And so this next slide links us to a YouTube video that kind of gives you a little bit more information about this brain-eating amoeba. Any of these videos that I click play on, or that you choose to click play on in this PowerPoint, I give you kind of a warning it could be a nasty video we'll just have to kind of It's up to you whether you watch But while its actions often have deadly consequences the amoeba hijacks the brain for a benign reason to find food and shelter. Inside the brain, the amoeba has a perfect environment to feed and reproduce. You have food, heat, moisture.
It's perfect for them to live their lives. The amoeba has a two-pronged attack. First, it hijacks the host cells using special feed called pseudopods. Then, the amoeba cuts a hole in the cell wall. And when the contents of the cell leak out, the amoeba eats them.
Not only are the amoeba ruthless killers, they also have a cunning method of evading the body's immune system. The amoeba can defend itself by forming a coat, which is called a cyst. And this coat surrounds the amoeba and... is impervious to the host's immune system.
When the body's white blood cells attack, the amoeba forms its protective coat. The white blood cells latch onto the coat, but can't get through. Then the amoeba sheds the coat.
and escapes unharmed, leaving the white blood cells behind. What happens is that when the amoeba gets into the brain, in a sense it's holding the brain hostage. So when the body sends in its immune system to try to defuse the hostage situation, often it does even... The amoeba lives in a cyst in sediment on the bottom of lakes. As the water warms, the amoeba merges from the cyst and begins to divide.
At this stage, the amoeba can infect humans. When conditions become unfavorable, the amoeba forms a cyst again, and the life cycle repeats. And even in warm water, some simple measures can protect swimmers.
The way to prevent deaths from occurring, first of all, is to educate the public about this disease. And secondly, it would be very important to wear nose plugs when doing recreational activities, such as diving or wakeboarding, where underwater... Okay, so if that doesn't disturb you enough, let's keep going. Let's look at a few more of the eukaryotes within the group protozoa.
So remember, we're still talking about the unicellular protozoa that are classified. by their movement by their type of movement so moving into our next group we're going to call this group the it's got kind of a complicated name but within this group we're gonna see we have AP complexins and ciliates. So first let's look at the AP complexins right here. AP complexins are not modal. They are gonna always be a parasite.
Meaning by non-modal that means they do not have pseudopods, flagella, or cilia. There's two groups, there's two different genus within this AP complexin group that I thought would be interesting for us to discuss. The first one is plasmodium. Plasmodium is the causative agent of a terrible disease known as malaria. So the way this infection works, malaria, the plasmodium, is transmitted through a mosquito bite.
So when the mosquito that has the malaria parasite, the plasmodium, inside of its gut bites a human, it can then put those parasites into the... human bloodstream. So the little green things in this picture that represents the plasmodium. The plasmodium will move to the liver, infect the liver, multiply within the liver.
So you see this word size size size on it that's the size of ghani that I was talking about that rapid multiplication. So this just a couple infect the liver and thousands will leave the liver and now go infect the bloodstream. The plasmodium will actually ingest red blood cells.
You think about it, if your red blood cells are being ingested, you're going to feel tired. Eventually, it's going to... It's going to cause some devastating effects to your cardiovascular system, but at first you're just not going to feel good from the Plasmodium eating your red blood cells.
Now that the Plasmodium is back in the red blood cell causing damage, another mosquito can come along and bite this individual. Now a new mosquito is infected, and it can go bite. other people. And so I have a video about malaria that I would like to play some of and let you watch.
It's a Saturday. I'm at home. I wake up in a cold sweat.
I get a fever and a headache. And now I start to get the chills. I'm concerned and I want to try to find out what this might be. On call is Dr. Daniel Koblipski, an expert on infectious diseases.
In listening to Kelly's story, we're hearing about fevers that are recurring every 48 hours. And there is a certain thing about fever patterns that are very important to listen to and understand. We asked Kelly if she had been anywhere outside the country in the past year. I tell them that nine months ago, I took my honeymoon to Africa. The doctors return to Kelly's blood sample.
Kelly has some very abnormal labs. It looks like there's a problem with her blood. There's evidence that red blood cells are being broken open.
As we try to figure out all these different abnormalities on her peripheral blood smear, the one thing that can put it all together is malaria. Malaria is caused by a tiny parasite called Plasmodium. I can't believe I have parasites in my blood. The parasite is transmitted from host to host by an insect, the mosquito. When an infected mosquito bites a human, the parasites enter the bloodstream and travel to the liver where they reproduce.
The new parasites then move back into the bloodstream and attack red blood cells. There, they multiply rapidly and eventually break the cell apart from within. And legions of new parasites re-enter the bloodstream and start the attack all over again. I'm very scared and very afraid. So that's just a little bit about malaria.
Again, malaria belongs to this group of apicomplexans. It's caused by plasmodium. Now there's one other group, one other genus in the apicomplexans I wanted to introduce to you. and that is called Toxoplasma gondii. Toxoplasma gondii causes a disease called toxoplasmosis.
So you may have heard at some point that as a pregnant woman or very young children, you have to... to be careful around cats and the reason for that is this disease toxoplasmosis. It's quite common for cats to be contaminated with the toxoplasma gondii parasite and then when the cat goes to the bathroom in the litter box and scratches and does its thing, if it's infected with the toxoplasma, that toxoplasma is now going to be moving through the air and it can be inhaled or it can be ingested depending on the type of toxoplasma. depending on if the cat litter box is near the kitchen or something kind of gross like that.
So it's common, mostly seen with pregnant women or very young children, if they come in contact with the cat litter or some sort of other contamination source, they can contract toxoplasmosis. Transmission of toxoplasmosis to a baby while still in the womb can lead to hydroencephaly, which is a... water fluid excess on the brain when the baby's born.
Children can see infections in the eye. It can get really nasty so you just really have to be careful with this infection. And so now moving to the ciliate, still within the same large group of protozoa. There's only one ciliate that is infectious to humans and that is called Ballantidium coli. Ballantidiosis is a gastrointestinal infection from eating typically vegetables or meat that's contaminated with the parasite.
Alright, so let's move on to our next group of protozoa. We're now going to look at the euglenoids. These are our flagellates.
They move with a flagella. There are very, very few free-living photosynthetic examples. Those are really rare.
But there's a parasitic flagellate that is very interesting. I wanted to talk to you about that. about and its name is trypanosoma.
Trypanosoma causes two different diseases with two different species of trypanosoma. It causes African sleeping sickness as well as Chagas disease. It's called African sleeping sickness in Africa.
It's called Chagas disease in South America. They're very similar. The real difference is the insect that transmits the infection with African sleeping sickness. the trypanosoma is going to be transmitted by the tsetse fly. It's this little fellow right here.
With Chagas disease, the trypanosoma is going to be transmitted by the kissing bug, the tritone bug. But it's the same life cycle either way. So this bug, in this example, the tsetse fly is going to bite a human, they're blood-sucking insects. When it bites the human, it places the trypanosoma into the bloodstream. The trypanosoma then begins to multiply within the blood and it ultimately travels into the spinal fluid and into the brain.
It causes patients to become delirious, kind of just not feeling right. Ultimately, it can cause them to fall into a coma, hence the term sleeping sickness. The life cycle is continued by whichever bug, in this example, the tsetse fly, bites another human.
And so I do have a video on African sleeping sickness, but just for the issue of time, I'm not going to play this one, but I highly recommend that you watch this one on your own time. So let's move into our next big group of eukaryotes that we need to take a look at, and these are the parasitic helminths. Helminths are worms. They are not microscopic at all times.
In fact, worms are multicellular animals. They have full organ systems. But we consider the parasitic helminths within a microbiology class because they are classified by their microscopic eggs and larva.
So that means when they are transmitted from one host to another, they can't be seen. So all those YouTube videos that show worm eggs and larvae moving inside of meat and all that, most of those are not going to be true parasitic helmets. Those are just goofy videos you can watch. So a little bit of terminology before we go through a couple of the really gross diseases. Within the parasitic helmets, we have two groups.
We have nematodes and platyhelminths. The nematodes, right here, are round ones. worms.
Here's a picture of the round worm. Round worms, there's going to be a female that's much bigger than the male. Pretty well developed organ systems.
Just like more like a normal worm you would think of. The platyhelminth right here, the flatworms, they're a little different. Within the flatworms you have trematodes, which are flukes, and you have cestodes, which are tapeworms.
The flat worms are dorsal ventricles. flattened and they have reduced organ systems just gotta think about because they're so flat they really don't have the room to have full organ systems also you can think about one of these you already know a lot about probably that's a tapeworm you know it lives inside of the intestines and it eats your food so it doesn't have to look for food that's not to move around for food it doesn't even have to digest food. You're doing all of that for it.
So it doesn't need those fancy organ systems. What's really neat about these platyhelmus is they can be hermaphrodites or monicious, depending on which term you want to use. This means that within the one organism, it has both male and female reproductive organs. So it can essentially reproduce with any other within its species. It's an advantage.
for it. It doesn't have to look for a mate. So this picture right here that the cursor is moving around, this is an example of a fluke. They're going to be smaller.
The largest is about an inch long when full grown. It has a sucker to hold on to its environment. So this is a lung fluke.
It's going to have a sucker to hold on to the tissue. And then it's also going to have a sucker to ingest. It eats whatever it's living on. If we look over here at the cesto.
the tapeworm they're going to be long so you're going to have these long preglottids these little regions then within each little preglotted we can see male and female organs the very top of the tapeworm the skolex has suckers as well as hooks so it can hold on with the tapeworm it's actually just going to absorb food across its surface. It's living in the digestive tract. Food is digested for it.
So giving you the warning that some of these are really gross. You don't have to watch this if you don't want to. But let's look at some of the parasitic.
helminths. Okay, so first let's look at the nematodes. Remember these are the round worms. There's two that I thought you might find interesting.
The first example parasite is Ascaris lumbricoides. Ascaris is a really nasty infection. These are large round worms. You get them from ingesting a contaminated food source that's been contaminated from fecal matter from someone who has an infection. Once you ingest the eggs, I don't know why it's on a carrot, but once you ingest the eggs, the eggs then go down into your digestive tract.
Really gross. The larvae are hatched inside of your digestive tract. They crawl back out.
Swallow it back down from say crawl up the good your bloodstream go to your lungs crawl up your trachea You'll swallow them back down now that they're back inside of your intestine. They're fully mature They can reproduce inside of your intestine So I have a video to show you I know like really kind of scared at this point, right? But this purse video is not too bad.
So I'm gonna hit play on it. This is a video showing you a Colonoscopy actually, I think it's of a cat but it would be look the same in human. These are the actual ascaris worms wiggling around inside of intestines. So super, super gross. Now this video, I'm honestly not going to hit play while we're doing this PowerPoint, but if you like a gross video, this is one for you.
This is a video of a human that is having surgery to remove an ascaris blockage. This is a very, very extreme case of this blockage. So they're having to surgically remove these large ascaris worms from someone's intestines.
So if you like the gross videos, there it is. You can go for it. The other parasitic helminth, nematode. that I want to talk about is Enterobius vermicularis. This guy right here.
Enterobius vermicularis is commonly known as the pinworm. Pinworms love to infect little kids. They can infect adults as well, but kids typically transmit them a lot faster than adults do.
So when you ingest the egg, it gets into your digestive tract. They reproduce inside of the digestive tract. And then when you go to sleep at night, the adult...
female worm will travel to the anus and will actually lay eggs on the outside of the anus. Well, when you wake up the next morning, you have no idea that's happened, but the presence of those eggs on the anus will cause itching. And then especially with little children, if it's itching, they're going to scratch.
Once they scratch, now the eggs are under the fingernails and they touch something else. They touch a toy, another kid puts it in their mouth, something like that. we get transmission of these pinworms. And so I have another colonoscopy video here showing you what these little pinworms look like wiggling around.
So you can just see them. They're just really active little guys. Much smaller worms than the ascaris was. Alright, so if you're not feeling good to your stomach yet, let's keep going.
Next group of parasitic helmets, the platyhelminthes. Let's look at an example of a fluke. All of your flukes are parasitic. They are going to feed off of what... tissue they're living upon.
So a lung flute eats lungs, blood flute eats blood, liver flute eats liver, and so on and so forth. So in this particular example, it's showing you this blood fluke known as schistosoma. So the way you get the schistosoma is you come in contact with this little teeny tiny nice looking snail in fresh water. So when you come in contact with the snail, swimming, anything like that, it can actually penetrate directly through the skin. Once it penetrates through the skin, burrow through the skin, it lives in the bloodstream.
While in the bloodstream, it can, it's going to ingest red blood cells, causes really bad swollen. and abdomen. It can cause inflammation of all the organs.
This is actually what's known to be the downfall of Napoleon. You want an interesting history story to read, this is one for you. And then just by being put back into the water, it can infect a new snail.
So I don't have a video for that one, but you can find some if you're interested in that. Our next group of platyhelminths, we want to look at these cestos. These are the tapeworms. So it listed three.
different types of tapeworm. So that this first one in the tinea group that's going to be your beef tapeworm. This next tinea that is going to be your pork tapeworm and then the last one diphyllobothrum latum that's going to be a fish tapeworm.
So you should see the trend you get a tapeworm from eating meat that is undercooked from an animal that has the infection. itself. So in this particular example, if this cow was infected or the pig either way and then you ingested some of that meat that was undercooked, now you would be ingesting just a very tiny microscopic portion of the tapeworm cyst and then you could grow a large tapeworm inside of the intestine. So a lot of people like to think tapeworms are bad for you because they eat your food and you don't get any nutrition. That might be a little bit true.
true, but what's really going on is not the fact that they're eating your food. Okay, you can eat more food. The reason tapeworms are bad for you is once they get large enough that they're not satisfied by being in your intestines, they can leave your intestines and move to other organs like your brain and start causing damage there.
And so I have another Monsters Inside Me video with a tapeworm that kind of explains that a little bit. So first, let me just show you a little bit from this YouTube. video. This is a colonoscopy with a tapeworm moving around in it.
You see how flat he is? That one just kind of creeps me out even a little bit. Let's watch this video talking about the pork tapeworm.
The monster's inside me. Pork tapeworm is a particularly nasty parasite. In 60% of the diagnosed cases of pork tapeworm, the victim has cysts inside the brain. And when you have a cyst in your brain, very bad things can happen.
You can have seizures, coma, hallucinations, or possibly even death. The pork tapeworm has two hosts, humans and pigs. The parasite forms cysts in the tissues of a pig. If a human eats undercooked pork that contains the cysts, they get infected. In the human gut, the cysts hatch into adult tapeworms, where they can grow up to several meters long.
The adult worms lay eggs that are passed in human feces. If a pig then eats the feces, the eggs grow into cysts in its muscle tissue, and the life cycle repeats. Where sanitation is not very good, this parasite can be very common.
In some parts of the world, up to 6% of the population harbor this parasite. In most cases, humans get the parasite by eating contaminated pork. But a few get infected when they come in contact with egg-laden human feces. If you eat undercooked pork, you end up with the tapeworm in your gut.
But if you eat the eggs that have been passed out in feces, then you can end up with the cysts in your tissues, and that can be a lot worse. The only way to kill the parasite is with a powerful drug called albendazole, which starves it to death. The pork tapeworm is one of the most common parasites to affect humans. It infects over 50 million people worldwide.
The best way to avoid it is to wash your hands before and after handling food. And if you eat pork, make sure that it's cooked all the way through. Alright, so I'm going to go ahead and stop that video there. about our last few groups and you can probably tell from the slideshow to me not quite as interesting I guess because we don't you see there's only a few slides left but there is a little bit of information that is very important for us to know with the last few groups of eukaryotes. There are some microscopic fungi that are can be parasitic so we like to talk about these within the microbiology course.
So let's talk about a fungus. One important term you need to know when you're looking at fungi is that they are saprobes. Meaning that the main thing a fungus is going to do is consume dead or decaying matter.
So it's not normally going to be something that's parasitic but it can cause disease. It's most common for people to end up with a fungus infection that is kind of secondary, meaning you're already sick from something else. Okay, so if we look at the different fungi, we're going to look at two groups, molds and yeast.
So this picture up here at the top shows you the mold. Mold is like you think of mold growing on your bread. But that's...
That's when it's not microscopic anymore. You can see all the little hair-like guys sticking out. What you're seeing on your bread is called the mycelium. It's just a large chunk of mold.
The mold was there long before you could see the... mold on the bread. Mold starts as the spore, which is kind of the beginning part, hatches or germinates, becoming the thallus, which is going to be the body of the mold. and then the body will grow out long extensions called hyphae.
As it continues to grow different reproductive spores will be within the hyphae and then that hyphae can burst releasing more spores so it's spread very rapidly. The yeast is very different from the mold it's unicellular. This is a micrograph image of a yeast but you guys have all heard of yeast. If you've eaten bread you've eaten yeast.
You've eaten Saccharomyces yeast. You can buy it at Walmart, freeze-dried in a little packet. Not all yeast is bad for you. Even some yeast that can cause infection under normal condition isn't bad for you.
And we'll talk about this a little bit more at a later date, but I want to mention it to you now, this yeast called Candida albicans. Candida albicans is the yeast that normally lives on you. But if things get out of whack, you start taking antibiotics, your P. gets affected somehow from different soaps or lotions lots of things other infections that you can get a yeast infection from candida albicans so this is a very important name for you to know One interesting thing that can occur with our parasitic fungi is that a lot of them are dimorphic, meaning they can morph back and forth between the mold and the yeast form.
And so this particular example... is really interesting is called histoplasma capsulatum. Histoplasma capsulatum grows in soil that's been exposed to either bat or bird feces. So it's really common if you have an older place that people are remodeling or something like that.
like that, if it's ever had bats in the attic and had an iguano, then you may have some of this more mold-like histoplasma present. The human inhales the spores from the mold type. Once inside of the body, the human body is higher, so it's going to turn more into the yeast form.
Well, inside of the human body, that yeast form grows very rapidly and can make you very, very sick, leading to... to what we call chronic lung infections. So histoplasm is a really neat fungus.
There's just not that many like that. group that we're going to talk about in this chapter are the algae. There are a few different types of algae but I really want to focus on a couple.
The three main types of algae you see with these first three bullets are categorized by their color. So brown algae these are going to be the kelp. These are large algae that live out in the ocean.
They are very macroscopic not what we're worried about in this class but just a side note if you've ever eaten ice cream you've eaten algae. Just throw that out at you. Alright but the red Red algae, they are something that we need to talk about in microbiology class. Not because they cause infections, they also are deep in the ocean, but microbiology media has something in it called agar.
So you guys have already started working with your lab kits. Your lab kits have agar plates. What makes them thick or hard? That's this agar from red algae.
Now green algae is what you're all familiar with. That's that kind of scummy stuff that you can see in ponds. It's not bad for us. It's good for us.
It produces a lot of oxygen, very photosynthetic. Our next two, the diatoms and the dinoflagellates, they're actually the unicellular microscopic ones. The diatoms, though, really what they're important for is they produce oil. They don't cause infection.
The dinoflagellates, represented by this picture here, this kind of aqua green picture, they produce oil. They are really the ones that can cause infection from this whole group. They are responsible for something called red tide.
Now, red tide is not just devastatingly dangerous to humans. It can cause some respiratory infections. You can inhale some things.
But red tide is very dangerous for fish. And where we're from around here in South Mississippi, it can become a huge issue. Every now and then we will have red tides down on the coast.
It can cause... a lot of problems with our fishing industry. So it is something that you need to recognize it's the causative agent of that red tide. So as you study this chapter, I highly recommend you sit down and organize the different groups.
If this were me, I would create kind of an outline. Roman numeral 1, protozoa. Subgroup A, first group RV, amoebozoa.
And just list some things under it. Really organize it in your brain so that you can properly study.