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Microbes By: Ita P. Rodríguez 3rd Grade Homeschool Biology What is a MICROBE? What makes a microbe? We suppose you need a microscope to see them. That's about it. There is a huge variety of creatures in this section. They can work alone or in colonies. They can help you or hurt you. Most important fact is that they make up the largest number of living organisms on the planet. If you spend your life studying them, you would be a microbiologist. Some of them, like viruses, may not even be alive as we currently define life. Page 2 Prokaryotes Prokaryotes do not have an organized nucleus. Their DNA is kind of floating around the cell. It's clumped up, but not inside of a nucleus. Can You Exist Without a Nucleus? You can't, but they can. Most prokaryotes are bacteria and bacteria can do amazing things. They are found everywhere on the planet. Some scientists even think that they may be found on other planets (maybe even Mars). Some places you can find bacteria every day are in your intestines, a cup of natural yogurt, or a bakery. Page 3 Prokaryotes Prokaryotes are the simplest of simple organisms. Here's the checklist. Prokaryotes have no organized nucleus. The DNA is clumped in an area but there is no organized nucleus with a membrane. Prokaryotes do not usually have any organelles. They will probably have ribosomes inside of their cells, but ribosomes are not technically considered organelles. Bacterium No chloroplasts. No mitochondria. No nucleus. Not much at all. Page 4 Prokaryotes Prokaryotes are very small because they don't have all of the normal cell machinery. Mind you, compared to a bacteria they are big, but next to an amoeba, tiny. In this picture, an ameoba is going to eat a prokaryote. Page 5 Eukaryotes Eukaryotes are what you think of when you think of a classic "cell" with a nucleus and organelles. What makes a eukaryotic cell? Eukaryotic cells have an organized nucleus with a nuclear envelope. They have a "brain" for the cell. Eukaryotic cells usually have organelles. They might have mitochondria, maybe a chloroplast, or some endoplasmic reticulum. Page 6 Eukaryotes Although limited in size by the physics of diffusion, eukaryotic cells can get very large. There are even some extreme examples called plasmodial slime molds that can be a meter wide. Generally, eukaryotic cells are a couple hundred times the size of a prokaryotic cell. Page 7 Eukaryotes Eukaryotic cells have extra stuff going on and extra parts attached. Since they have organelles and organized DNA they are able to create parts. One example is the flagellum (a tail-like structure to help it move). They could also create cilia (little hairs that help scoot the cell through the water). Page 8 Virus Are Viruses Alive? We're starting with the smallest of the small here. Some scientists argue that viruses are not even living things. It's easier to give you a list of what they can't do as opposed to what they can. What viruses can't do: They can't reproduce on their own. They need to infect or invade a host cell. That host cell will do all the work to duplicate the virus. They don't respond to anything. You can poke them or set up barriers, it doesn't matter. They either function or they are destroyed. They don't really have any working parts. While there are some advanced viruses that seem fancy, viruses don't have any of the parts you would normally think of when you think of a cell. They have no nuclei, mitochondria, or ribosomes. Some viruses do not even have cytoplasm. Page 9 Virus Every virus has a few basic parts. The most important part is a small piece of DNA or RNA (never both). That strand of nucleic acid is considered the core of the virus. The second big part is a protein coat to protect the nucleic acid. That coat is called the capsid. The capsid protects the core but also helps the virus infect new cells. Page 10 Virus Types of Viruses: Helical virions: They are set up like a tube. The protein coat winds up like a garden hose around the core. Polyhedral virions: This shape group includes the classic virus shape that looks like a dodecahedron (has 12 sides). Complex virus: You may have seen this one in books with the geometric head and long legs. Page 11 Viruses Makes Us Sick Symptoms may include: Fever Runny nose Coughing or sneezing Headache Nausea or vomiting Diarrhea Pain in the body Internal bleeding Blisters Page 12 Viruses Makes Us Sick Since viruses aren't alive, medicine won't kill them. You can only treat the symptoms. The best way is to prevent an infection. Preventing a viral infection: Wash hands Keeps hands away from mouth, nose, and eyes Avoid sharing personal items like a toothbrush Avoid sharing food and drinks with other people Page 13 Viruses Makes Us Sick Viruses can affect any living organism. Page 14 Bacteria They Are Alive! Bacteria are the simplest of creatures that are considered alive and they are everywhere. They are in the bread you eat, the soil that plants grow in, and even inside of you. They are very simple cells that fall under the heading prokaryotic. Bacteria are small single cells whose whole purpose in life is to replicate. Page 15 Bacteria Types of Bacteria: Spherical shaped: They are in the shape of little spheres or balls. They usually form chains of cells like a row of circles. Rod shaped: This shape group (like the E. coli living in your intestine) are a bunch of bacteria that look like hot dogs. They can make chains like a set of linked sausages. Spiral: These twist a little. Think about balloon animals for these shapes. It's like a balloon animal in the shape of a corkscrew. Page 16 Bacteria What do good bacterias do? Some help plants absorb nitrogen from the soil. Some bacteria even live inside the stomachs of cows to help them break down cellulose. Page 17 Bacteria What do bad bacteria do? Some cause diseases. Symptoms are the same as viral infections: Fever Runny nose Coughing or sneezing Headache Nausea or vomiting Diarrhea Pain in the body Internal bleeding Blisters. Since bacteria are alive, you can kill them with medicine called antibiotics. Page 18 Protozoa Protists Protozoa are also known as protists. These are the bad boys of the microbe world (bad meaning "advanced"). Protists are eukaryotes with special structures that may be the base organisms of multicellular organisms. Page 19 Protozoa Slime Molds Slime molds are not molds like a fungus. They are actually independent organisms. There are two big kinds of slime molds. Cellular slime molds are actually thousands of individual cells that team up and work together. They specialize for a short time and some do the eating, some work on reproduction, and some build special structures. Acellular slime molds might also be called plasmodial slime molds. They can be huge, a couple of feet across, but they are still only one cell. They are able to grow so large because the one cell is multinucleated. They ooze across the ground of forests digesting everything they can. When it comes time to reproduce, they release all sorts of spores (like a fungus). Acellular Cellular Page 20 Protozoa Amoebas Amoebas are small-single celled organisms that ooze from place to place. They reach out with one part of the cell, a structure called a pseudopod (it's like a foot). They don't really have a shape because they are constantly on the move, hunting down food and eating by a process called phagocytosis. They wrap themselves around the food and absorb it into their body for digestion. Page 21 Protozoa Protists with Tails The next protists are called flagellates because they move with a specialized tail called a flagellum. They live in water and the water inside of dirt. The flagella whip around like a not-so-coordinated fish tail. When it whips, the protist scoots along though the water. They do not do well in dry areas. They need that liquid environment to move. Page 22 Protozoa Protists with Hairs Cilia are short little hairs. The classic example of a ciliate protist is a Paramecium. They are the very complex protists that have little hairs all over their body. The hairs flap and push the organism through the water. They can even hunt down food and attack them with a structure called a trichocyst. Instead of surrounding their prey like an amoeba, they take in the food through an oral groove (a protist version of a mouth). They even have a way of getting rid of the food through an anal pore. They might not seem like much to you, but the structures are very advanced for a single-celled creature. They were the first creatures to have them. Page 23 Protozoa Parasitic Protists Last, we'll talk about the parasites of the protist world. Not all protists go about their life eating little bits of food in a pond. Some, called sporozoans, are nasty little parasites. These protists, like all parasites, cannot live on their own, and they harm the host organism over time. A disease called malaria is caused by one example of a sporozoan protist. Page 24 Fungi Fungus Among Us There are no such things as molds. All molds are actually fungi. We always heard about mold in the shower or mold on the bread. Mold is actually a type of fungus. It has a shape called a zygote to be exact. While yeasts are single celled fungi, molds are multicellular fungi. Bread takes one kind of fungus (yeast) to make it rise. If you leave the bread out, another type of fungus comes in (bread mold) to break it down. It's not amazing, but it's true! Page 25 Fungi Mushrooms So what is a mushroom or a puffball? Bunches of strands living underground are called hyphae (pronounced hi-fah). Those strands are the basic fungus in action, decomposing leaves, or rotting bark on the ground. When it's time to reproduce, they develop a stalk and cap. The mushroom that you see popping out of the ground. On the bottom of that cap are a set of gills that have little clubs with fungus spores. Page 26 Fungi Zygotes These have hyphae-like mushrooms but they reproduce in a different way. When it's time to make more fungi, they create a stalk and release something called zygospores (thus the name zygote). When your bread gets old and green or black, you are seeing a type of zygote fungus in action. If you wait long enough, you will see the stalks develop and the zygotes released. Page 27 Fungi Single Cells Sac Fungi are single celled fungi. Yeast is used to make several types of food for humans. We need yeast to make breads. We also use them to make alcohol. It's a whole process called fermentation. Sugars are broken down in an environment without oxygen. It's called anaerobic fermentation. And voila, alcohol. Even though they are single celled, you may find them in colonies. They reproduce very quickly and hang out together. It takes a lot of them (because they are so small) to get a lot of work done. Page 28 Lichen Lichens are special organisms. They are actually two types of organisms in one. It's all about a fungus and some algae. Lichen is two organisms working together. When you read about fungi we talked about hyphae. Hyphae are strands of the fungi that form a mesh as they grow. In lichen are actually cells of algae living between those strands. The two organisms work together. The fungus acts as a protector from the environment and loss of moisture. The algae go about their business of photosynthesis and creating food. The fungus uses the energy and the algae are protected and can survive. Page 29 Lichen Lichens can live in places that many organisms cannot. Lichens can even live on the side of a rock. They don't need soil. Slowly the fungus can break down the minerals in the rock. The algae provide energy. They are a self-sufficient team. Scientists may call that team a composite organism. They are both able to be in places they could not go alone. It's an advantage for their survival. Page 30 Lichen Are we killing off the lichens of the world? In some places, yes. Indirectly we may be killing many species of lichen in the same way that air and water pollution are killing off many species of amphibians. Lichens are very delicate organisms. Changes in the levels of poisons and toxins hurt the relationship that the fungi and algae have. Always remember, even if the fungi can survive the poisons, if you hurt the algae, the whole organism will die. They are dependent on each other. Page 31 Good Microbes Fixing nitrogen in soil: There are bacteria that go through a process called fixing nitrogen. These bacteria, living in the roots of plants, actually help them absorb nitrogen from the surrounding soil. The nitrogen is very important for the growth of the plant, and these little bacteria give them an advantage for survival. Helping cows eat grass: In the bacteria section we already told you about a species that lives in the digestive system in cows. These bacteria help cows break down the cellulose in plants. Similar bacteria live in all sorts of grazing animals, helping them survive off plant material. Page 32 Good Microbes Antibiotics: Scientists have even discovered fungi that will help you battle bacterial diseases. So you get sick, the doctor looks at you and says you have a bacterial infection, maybe bronchitis. He prescribes an antibiotic to help you get better. Antibiotics are drugs designed to destroy bacteria by weakening their cell walls. When the bacterial cell walls are weak, your immune cells can go in and destroy the bacteria. Although there are many types now, one of the first antibiotics was called penicillin. It was developed from a fungus (a fungus named Penicillium found on an orange, to be exact). Page 33 Bad Microbes Diseases: Many species of bacteria cause disease in humans, animals, and even plants. Humans worry about bacteria that cause botulism (bacteria living in spaces without oxygen, such as cans), tetanus and E. coli. You should know that there are also some good forms of E. Coli living in your intestines. They help break down food and live a simple life (and yes, they make it smell down there). There are also E. Coli that can be passed to you from undercooked meat. These bad bacteria can make you very sick and even kill you. Page 34 Bad Microbes A Role in Natural Selection: We don't know of any viruses that are good for the world. They are an important piece of evolution and natural selection. Weaker and older animals are more easily infected. Those organisms are removed from the population so that healthier animals can survive. But the virus life cycle only hurts the organisms. Some even destroy cells in order to reproduce. And don't think you are the only one to get sick. Viruses attack plants and even bacteria. Page 35 Man and Microbes Scientists all over the world are experimenting with viruses, bacteria, and fungi for hundreds of reasons. Why mess around with these little creatures? They are the simplest of all organisms. They can also be the most deadly. That is reason enough to study them. Microbes to make medicine Scientists are working with microbes and the compounds they create to make new medicines to save our lives. You might be vaccinated for pox or the flu. Scientists have studied those viruses to see how they act. Then they came up with a way to teach your immune system to do battle. If you get sick at all, you will be able to fight off the infection. Labs are also developing drugs that help you fight infections after you get the disease. We already spoke about antibiotics. Labs are creating new and stronger antibiotics every day. Page 36 Man and Microbes Microbes in War Although nobody likes to talk about it, humans have a history of using disease and compounds created by microbes in warfare. Labs were built to create chemical compounds that would kill people. They also isolate diseases (viruses) that could be released to infect entire populations of people. Most of the world has chosen not to develop diseases for use in war. They realized how dangerous and uncontrollable these diseases are. Once they are out, they might not be able to be stopped. Page 37 Man and Microbes Cleaning the Environment Scientists are also working with microbes to help the environment. In reality, the environment did not need help; we're just trying to lower the negative impact we have on the environment. Good examples are the bacteria that have developed to break down oil in the water. If a tanker leaked and oil began to get into the water, these bacteria could be released to break down the oil. The resulting compounds would not hurt the environment. Scientists are also working with bacteria and fungi to help breakdown garbage. Page 38 THE END Page 39