Fusarium sp
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What Is A Microbe?
by American Society For Microbiology
Our Challenge: How are we going to solve the case of what a microbe is when they're so small they're invisible to us?
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Microbe is a term for tiny creatures that individually are too small to be seen with the unaided eye. Microbes include bacteria(back-tear-ee-uh),archaea (are-key-uh), fungi (fun-jeye) and protists (pro-tists). You've probably heard of bacteria and fungi before. Archaea are bacteria-like creatures that have some traits not found in any true bacteria. Protists include primitive algae (al-gee), amoebas (ah-me-buhs), slime molds and protozoa (pro-toe-zoh-uh). We can also include viruses (vye-rus-is) as a major type of microbe, though there is a debate as to whether viruses can be considered living creatures or not.
To solve the case of what a microbe is, we have to use tools such as high-power microscopes. Let's zoom in on some microbes and see what a few of these strange creatures look like.
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Virus
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Bacterium
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Alga
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Protozoan
| As you can see, microbes come in many varieties. They may live as individuals or cluster together in communities. |
So how small are microbes? Well, let's say we could enlarge an average virus, the smallest of all microbes, to the size of a baseball.
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An average bacterium would then be the size of the pitcher's mound.
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And just one of the millions of cells that make up your body would be the size of the ballpark!
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| What are Fungi?
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Fungal hyphae
Courtesy of Alex Hausler, Givaudan Roure
| When you hear the word fungus, you probably think of mushrooms. Did you know bread mold is a kind of fungus, too? And that the itchy burning of athlete's foot is, yes, caused by another fungus? And that when you take penicillin, you're taking a medicine made by a fungus?
Fungi come in a variety of shapes and sizes and different types. They can range from individual cells to enormous chains of cells that can stretch for miles.
Classification
Fungi are eukaryotic (you-carry-ah-tick) organisms—their DNA is enclosed in a nucleus. Many of them may look plant-like, but fungi do not make their own food from sunlight like plants do.
What They Look Like
Fungi include single-celled creatures that exist individually—the yeasts—and multicellular bunches, such as molds or mushrooms. Yeast cells look like little round or oval blobs under a microscope. They're too tiny to see as individuals, but you can see large clusters of them as a white powdery coating on fruits and leaves.
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Paecilomyces variotii
| Molds are described as filament-like, or filamentous, because they form long filament-like, or thread-like, strands of cells called hyphae (high-fee). These hyphae are what give mold colonies their fuzzy appearance. They also form the fleshy body, or mushroom, that some species grow. It may seem odd to think of something as big as a mushroom as a microbe. But the cells of the hyphae making up that mushroom are connected in a closer way than the cells of other multicellular creatures, like you and me, are. The cell walls separating the cells in hyphae usually have openings that allow the protoplasm <pro-toe-plazm>, or fluid that fills cells, to flow between them. Essentially, a fungal hypha is like a tube. Your cells, on the other hand, are completely walled off from each other and the cell fluid, or cytoplasm <sigh-toe-plazm>, inside doesn't mingle between cells.
Where They're Found
Fungi usually grow best in environments that are slightly acidic (a pH measurement of 5 or so; a pH of 7 is neutral). They can grow on substances with very low moisture. Fungi live in the soil and on your body, in your house and on plants and animals, in freshwater and seawater. A single teaspoon of topsoil contains about 120,000 fungi.
How They Spread
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Fungal spores
| Fungi are basically static. But they can spread either by forming reproductive spores that are carried on wind and rain or by growing and extending their hyphae. Remember that hyphae are chains of fungal cells. Hyphae grow as new cells form at the tips, creating ever longer and branching chains of cells. It takes a lot to stop them, too. Hyphae are tough enough to punch through plant cell walls and the hard exoskeletons of insects.
What They Eat
Fungi absorb nutrients from living or dead organic matter (plant or animal stuff) that they grow on. They absorb simple, easily dissolved nutrients, such as sugars, through their cell walls. They give off special digestive enzymes to break down complex nutrients into simpler forms that they can absorb.
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Yeast cell (blue highlights scars where buds formed)
Microbiol. Rev. 54:381-431, 1990
| Friendly Fungi
Some fungi are quite useful to us. We've tapped several kinds to make antibiotics to fight bacterial infections. These antibiotics are based on natural compounds the fungi produce to compete against bacteria for nutrients and space. We use Saccharomyces cerevisiae (sack-air-oh-my-seas sair-uh-vis-ee-ay), aka baker's yeast, to make bread rise and to brew beer. Fungi break down dead plants and animals and keep the world tidier. We're exploring ways to use natural fungal enemies of insect pests to get rid of these bugs.
Fungal Enemies
There are some nasty fungi that cause diseases in plants, animals and people. One of the most famous is Phytophthora infestans (fie-tof-thor-uh in-fes-tuhns), which caused the Great Potato Famine in Ireland in the mid-1800s that resulted in a million deaths.
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For more information, contact:
Alan L. Wozniak, CIAQP
(800) 422-7873 ext. 802
info@pureaircontrols.com
[PRINTER FRIENDLY VERSION]
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