FUNGI KINGDOM

What is a fungus?

To answer this question, let's start with something familiar: a common mushroom. Everyone has seen mushrooms in gardens or fields and knows that they mostly appear in autumn, with each mushroom lasting for a short time before rotting away to a sloppy mess. Typically, there's a stem, a cap and gills under the cap.

When you look at such a mushroom growing out of the ground, you are looking at just part of a fungus - not the whole organism. The rest of the organism (often 90% or more) is underground and consists of a network of microscopically thin "threads" which spread through the soil. An individual thread is called a hypha and the network of hyphae is called a mycelium. The mycelium is there throughout the year, feeding and expanding. You will often see the mycelium referred to as the vegetative part of the fungus.

Under suitable conditions the underground mycelium will produce mushrooms, which are also composed of hyphae. The function of a mushroom is to produce and disperse spores, from which new fungi can develop.

One way to put this into a more familiar framework is to make an analogy with an apple tree. You know that the apple tree in your garden is there throughout the year but apples are produced for just a short time. So the mycelium is there throughout the year but mushrooms are produced for just a short time. The role of the apples is to produce seeds from which new apple trees can develop, analogous to the role of a mushroom, as explained above. Your apple tree typically produces many apples, so a single mycelium can produce many mushrooms. In some years your apple tree may produce no apples, because of poor conditions - but even in such years your apple tree is still there. So, in some years a mycelium may produce no mushrooms, because of poor conditions - but the mycelium is still there, in the ground. The comparison between mushrooms and apple trees is a useful explanatory analogy, but it can't be pushed too far because plant seeds and fungal spores are fundamentally different.

In a mushroom, the spores are produced on the gills that are on the underside of the cap. When mature, the spores are released from the gills, fall down under the force of gravity and, when clear of the bottom of the cap, are then carried away by air breezes. Mushroom spores are tiny, typically less than a hundredth of a millimetre long, and so are easily dispersed by even the slightest of breezes. The role of the mushroom stalk is to raise the cap above the grass, twigs or stones that are close to the ground. If the cap is raised a suitable distance, the spores released from the gills have a good chance of being carried away a substantial distance - rather than getting trapped by obstacles such as the grass, twigs or stones mentioned above.

Therefore you can see that Fungi are a group of organisms and micro-organisms that are classified within their own kingdom, the fungal kingdom, as they are neither plant nor animal. Fungi draw their nutrition from decaying organic matter, living plants and even animals. They do not photosynthesize as they totally lack the green pigment chlorophyll, present in green plants. Many play an important role in the natural cycle as decomposers and return nutrients to the soil, they are not all destructive. Fungi are even used for medical purposes, such as species within the penicillium genus which provide antibiotics, e.g. penicillin.

Penicillium notatum is a species of fungus that was used as the original source of the antibiotic penicillin.

Species within the genus Penicillium produce flavours for blue and white cheeses, such as Gorgonzola.

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