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Fungi can be found in rising bread, moldy bread, and old food in the refrigerator, and on forest floors. Most decompose non-living things, but some damage crops and plants. A few cause problems in people, such as Candida, which causes yeast infections.
If you’ve ever baked bread, you’re probably familiar with the only fungi that’s truly a single-celled organism: yeast.
Other microscopic fungi (including those that form large visible colonies such as molds and mildews) form thread-like filaments of loosely connected cells called hyphae.
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.