Copyright © 2007 Dorling Kindersley
Fungi grow without sunlight and feed on organic matter. A typical fungus is made of many threads growing on or in a food source. Each thread, called a hypha, oozes chemicals that break down the food. This releases nutrients that the hyphae can soak up. Fungi include MOULDS, mushrooms, toadstools, puffballs, and truffles. About one in four fungi lives in partnership with an alga – these partnerships are called LICHENS.
Hyphae branch to form a network called a mycelium. The combined surface area of all the hyphae allows the fungus to digest and absorb a lot of food. Many fungi play a vital role in food webs. Their digestive action is the first step in breaking down dead plant and animal matter, making it useful to other life forms.
Grapes often have a fine coating of yeast. Yeasts are a type of fungus which grows in colonies of single cells. They thrive where there is a good supply of sugar, such as on the surface of fruit. As yeasts consume sugars they can create a toxic by-product that people value – alcohol. Yeasts are essential for producing alcoholic drinks, such as wine.
Fungi produce fruiting bodies, such as puffballs, which we can see above ground. These fruiting bodies release tiny spores that are carried in the air and start to grow wherever they fall. A single fruiting body can produce millions of spores, so it is likely that some will land on a suitable food source.
Fungi called moulds do not produce large toadstools. Their tiny fruiting bodies look like peppery spots and are usually black or blue. Mould grows wherever spores land on suitable food, such as bread or fruit. The mould’s threads, or hyphae, give it a woolly appearance.
Greenish Penicillium mould grows outwards across the surface of a dish of nutrient gel. This mould releases a chemical called penicillin, which is an antibiotic. Antibiotics are used to kill bacteria that cause diseases, without causing harm to the organism or person infected with these bacteria. Moulds are now grown in huge vats to produce this medicine.
In 1928 Fleming discovered medicine’s first antibiotic, penicillin, which has since saved millions of lives. He had noticed that one of his laboratory dishes of bacteria was infected with a mould. Around the mould, the bacteria had disappeared. Fleming realized that the mould produced a substance that killed bacteria.
Some fungi can combine with algae to form structures called lichens. Lichens can be flat or fluffy, living on rocks and tree trunks, and in environments too harsh for plants. They are often the first organisms to colonize a tough new habitat, such as a building’s roof or walls.
Both the fungus and the alga benefit from living together as a lichen. The green alga photosynthesizes and makes sugar, some of which it gives to the fungus. In turn, the fungus gathers up nutrients and moisture and passes them to the alga. This type of two-way relationship between life forms is called symbiosis.