Fungi can be single celled or very complex multicellular organisms. They are found in just about any habitat but most live on the land, mainly in soil or on plant material rather than in sea or fresh water. A group called the decomposers grow in the soil or on dead plant matter where they play an important role in the cycling of carbon and other elements. Some are parasites of plants causing diseases such as mildews, rusts, scabs or canker. In crops fungal diseases can lead to significant monetary loss for the farmer. A very small number of fungi cause diseases in animals. In humans these include skin diseases such as athletes’ foot, ringworm and thrush.
- How a mycelium is formed and how spores are distributed
- The yeast Saccharomyces cerevisiae.
Budding yeast Saccharomyces cerevisiae. Scars yellow can be seen on the surface. It is used in the production of beer, wine and bread.
- Macroscopic filamentous Fly agaric fungus (Amanita)
- Multicellular filamentous mould.
Rhizopus nigricans growing on bread left in a moist plastic bag for 7 days. Tangled mycelium are visible as well as sporangia bearing spores.
- Honey mushroom fungus
The largest organism in the world, when measured by area, is the Honey mushroom fungus, Armillaria.
Types of fungi
Fungi are subdivided on the basis of their life cycles, the presence or structure of their fruiting body and the arrangement of and type of spores (reproductive or distributional cells) they produce.
The three major groups of fungi are:
- multicellular filamentous moulds
- macroscopic filamentous fungi that form large fruiting bodies. Sometimes the group is referred to as ‘mushrooms’, but the mushroom is just the part of the fungus we see above ground which is also known as the fruiting body.
- single celled microscopic yeasts
Multicellular filamentous moulds
Moulds are made up of very fine threads (hyphae). Hyphae grow at the tip and divide repeatedly along their length creating long and branching chains. The hyphae keep growing and intertwining until they form a network of threads called a mycelium. Digestive enzymes are secreted from the hyphal tip. These enzymes break down the organic matter found in the soil into smaller molecules which are used by the fungus as food.
Some of the hyphal branches grow into the air and spores form on these aerial branches. Spores are specialized structures with a protective coat that shields them from harsh environmental conditions such as drying out and high temperatures. They are so small that between 500 – 1000 could fit on a pin head.