The Home Lives of Fungi

David Beeson, March 2022

The fungi are the organisms that form the Kingdom MYCETEAE, and are neither plants nor animals, and bear very little resemblance to bacteria or algae. So, they are fascinating when you get to know them. And, that is my task today – to enable you to see life from a fungal’s point-of-view.

(Previous articles have elaborated on the generalised structure of a filamentous fungus and of slime moulds, so we can skip that. But, recall that some fungal strands (hyphae) are not divided into cells yet others do have cross walls. They have a true nucleus, mitochondria, ribosomes and other organelles but their nuclear divisions (mitosis and meiosis) are rather odd.)

Myceteae are sub-divided: slime moulds, Ascomycetes, Basidiomycetes and some others I’d prefer to forget! All three types you should find in a damp UK autumn, and some others on some bread or cheese left out far too long (Bread moulds, mucor & penicilliums).

Fungi are never photosynthetic but release digestive enzymes to solubilise their food, just as we do along our gut. There are three lifestyles: parasites that leave the host alive, necrotrophs (necro = death, troph = feeder) feed and kill their host and saprotrophs that attack dead material and decompose it.

How do the fungal enzymes work? Well, plant cell walls contain chains of glucose-like molecules as insoluble cellulose and similar chemicals. Being long chains, they are insoluble and are great for making plant structure. (The last thing a plant wants is for its leaves to dissolve in the first rainstorm.) Fungal enzymes break these chains into their individual units, absorb them and use those materials in their own metabolism. So, dead leaves are broken down and their stored resources recycles, fungi cause rot on fruit and digest the trunks of living trees. And a bit closer to home, some attack us – Athlete’s Foot, Thrush and Ring Worm (yes, it is a fungus and not a worm.) Yeasts are unicellular fungi, and they break down sugars and starches in wine and bread manufacture.

With hundreds of thousands of fungal species there will be one that can attack almost everything. Some fungi live in thermal pools, others in Antarctica and some in your freezer, if not at minus 18 Celsius.

A healthy plant may be able to fight back against infection by killing its own cells or laying down cork near the fungus, so depriving it of most food supplies. Other plants manufacture expensive fungal toxins, but potatoes easily succumb to Potato or Tomato Blight through the stomatal pores of the leaves and soon wave the white flag. Human skin has an anti-fungal immune response, yet warm damp spots may allow the fungus to evade it.

While the vast bulk of the ‘traditional fungus’ is hidden from us, they do need to show themselves to allow their reproductive spores to be dispersed – the fruiting body. The fruiting body is composed only of hyphae, but they can be of three types. 1) Thicker-walled structural hyphae, 2) small, sticky and much branched binding hyphae and 3) hyphae that produce the spores. There are no specialised transport tissues like a plant’s phloem or xylem.

As far as I know, it requires two different strains (forms) of hyphae to meet and to fuse nuclei in sex before a fruiting body develops. These hyphae grow into the fruiting body and at their tips undergo meiosis (reduction cell division) to for the spores. Released spores can potentially germinate to form a new fungal organism or remain viable but ungerminated for years. Clever!

It is traditional to make spore prints in the autumn by laying a basidiomycetes fungus on paper. (The technique does not work with the other types.) The colour of the spores is an important factor in the organism’s identification. (Spraying with hair spray will preserve your print.) Spores may germinate in a dilute sugar solution on a microscope stage.

Remember, go to HOMEPAGE at http://www.nwhwildlife.org for 140+ ad-free articles. You will find some on growing your own edible fungi, slime moulds and other articles on fungi.