Botany 2 – They eat like animals and look (a little) like plants. And some wander around, as well. Amazing organisms! What are they?

David Beeson, mid-May 2021

Yes, you’ve guessed it … they are FUNGI.

At one time the fungi were considered as part of the plant kingdom. Sure, they do produce spores (as are pollen grains and those liberated by ferns, horsetails and mosses) and a few have cellulose cell walls, but they contain no chlorophyll, and most digest their own food using exo-enzymes. For those of you who studied A-level Biology, you will be shocked to learn that mitosis and meiosis are unusual in this group. Indeed, they are an odd mob! Especially when one understands that some do move around like an amoeba and then morph to look like a mould … almost like an insect changing from a larval form to a flying adult.

There are at least 100 000 named species, with an estimated 200 000 remaining to be discovered. And, they are evolving into new species (speciation) at a rapid rate. If you want a career in science, choose to be a fungal expert. There’s plenty to study.

Fungal nutrition

Not a trace of photosynthesis here. No chlorophyll, no need to sit in the daylight, but they do need supplies of energy and nutrients, so they either steal it (parasites), share it (symbionts) or eat it by digesting decaying matter. The stealers can quite contentedly steal and eventually kill the host, and then eat up the decaying remains. Now, do not think this has nothing to do with you … think Athlete’s Foot, think Ringworm, think Candida (thrush), think gone-off refrigerated foods that are covered in hairy growths. Yuk! And some of these human infections by fungi are untreatable – people die.

Human fungal infection

Once, in a Black Museum in a hospital, I saw the preserved head of a sailor who had caught a facial infection of a fungus. He had lost half his face, including an eye to the infection. There were several other gruesome specimens, including an eaten-away penis.

Some of the parasitic fungi secrete chemicals that ensure their host’s cells leak, and the fungus absorbs the released nutrients. Others inject a hypodermic needle (haustorium) and suck up their share of the food, others secrete enzymes and break down their food supplies before taking them in. Yet others kill off the host’s cells with toxins and feast on the remains – soft rot on fruit is an example. (Including the ‘noble rot’ of some ultra-sweet wines.)

As if that is not enough, some make friends with algae and form the lichens.

As I said, a good career is here for someone, especially when you add the fact that many fungi produce antibiotics, and fungi are used in human food manufacture (yeasts etc).  

They Call It 'Noble Rot' Wine (Botrytis) | Wine Folly
Grapes with Noble Rot – fungus breaks down the structure allowing water loss and an increased concentration of sugars. This means, on fermentation, sugar is left in the wine, which is very sweet.

Organization

The yeasts are single-celled, otherwise fungi are filamentous – long, undivided lines of ‘cells’ (hyphae) that mass to form a mycelium. They own a nucleus, so their DNA is enclosed – unlike the nuclear material of bacteria. Most other cell structures are present – mitochondria, ribosome, endoplasmic reticulum but no chloroplasts.

Fungal life cycles – spores and more — Science Learning Hub
Fungal Hyphae Photograph by Dennis Kunkel Microscopy/science Photo Library

Generally, the bulk of the fungus is unseen. The hyphae are deep inside the host, be it dead or alive, with just the spore-producing body on show. (Of course, some fungi, such as yeasts, do not grow fruiting structures). Yet in two groups, the ascomycetes and basiomycetes, a highly organised spore body is grown. That structure can grow up to 1 metre in diameter in one mushroom type.

With the fruiting body full of potential food, it needs protection. Melanins do that job.

Microscope investigation: Looking at the basidia of a culinary mushroom.

You’ll need some sharp razor blades. Do not use old ones! Worn blades mean ragged cuts. Also, you’ll need slides and cover slips.

Slice very fine sections of the gills. Take lots, and then select the very thinnest.

Mount in water and observe under low power. Look around (always do this! It will save time and effort. Honestly.) to seek out the best bit to observe. You should see the club-shaped basidia and spores attached to the outer surface.

If you leave the cap on a sheet of paper this will give you a spore print and allow you to scrape a few spores onto a slide. If you have a graticle (in the eyepiece) and a measuring slide you can accurately work out the size of the spores.

You can try this technique on other fungal types, always recalling that some fungi are VERY TOXIC.

Damp bread will often grow Mucor or Rhizopus fungi. Samples, in a drop of water, will show their sporangia (Spore bodies).

Is It Safe to Eat Moldy Bread?
Bread mould

Fungal metabolism and ecology

They can be anaerobic or aerobic in their respiration (energy release, not that dreadful misuse of the scientific expression to do with breathing!). Anaerobic respiration often liberates ethanol (alcohol) and carbon dioxide.

Humans are very reliant on fungi to break down waste materials. My compost bins would be useless without them.

When I was growing UK orchids from seed I employed fungi to partner the orchid. Initially, I had to sterilize the orchid seeds in dilute chlorine, and then sow them onto a selected medium in sterile petri dishes. Then I inoculated specific fungi onto that plate, under sterile conditions in a laminar-flow chamber, and they grew INTO the orchid seed feeding it. After many months the seed would grow into an undifferentiated cellular mass and, given a bit of luck, would finally generate roots and shoots. Only then was the fungus repaid as photosynthesis started.

[More details from The Hardy Orchid Society in the UK] Or, better still, you can buy my book: Obsession, a gentle thriller about orchids. dandabeeson@gmail.com.

Economic importance

Fungi are vital to recycling, to the growing of most trees, shrubs and herbaceous plants. Mycorrhizal associations with roots are increasingly being studied. Fungi cause economic loss in fruit damage and in destroying grain crops, e.g., wheat rust.

Antibiotics and yeast fermentation are million-pound businesses.

Is a Yeast Infection Contagious? Symptoms, Treatment, & Causes
Yeast – there are many different species.

And now something special, just for you:

Slime molds (moulds)

These are exciting, and I grew some for a while. They are quite unlike other fungi and I recommend you spend some time finding out more.

The body of the organism is a large mass of protoplasm of several cubic centimetres with scattered nuclei. Amazingly it is capable of flowing around in an animal-like manner – aiming towards a food supply. [I grew them on blotting paper in a damp and warm petri dish, and fed them on crushed fresh oat seeds.] They eat plant material, bacteria and yeasts. Eventually, often when poor environmental conditions occur, they stop and grow a typical fungus fruiting body and shed spores. Stunning!

I was donated a pet slime mould by: https://warwick.ac.uk/fac/sci/lifesci/outreach/slimemold/wildslime but this page will introduce you to the wonderful world of slime moulds.

Slime Molds Remember — but Do They Learn? | Quanta Magazine
Slime mould

THIS IS A COPY of one of Ian’s slime mould finding method. Produced with permission.

Moist Chamber Technique

By putting samples in a warm, damp environment for a bit you can give yourself a better chance of finding your own wild slimes. The moist chamber technique is how we do this. It’s good for finding slimes but it can take a while – they sometimes show up after eight weeks or more, and you’ll get all sorts of other things showing up – including protostelids and cellular slime moulds.

Safety

Slime moulds are harmless but other moulds, and bacteria that grow might not be. Always wash your hands after handling your tubs, definitely don’t eat anything that grows or stick your nose in the tub.

Equipment

  • Water tight tubs
  • Kitchen towel
  • Magnifying glass or microscope
Slime mould moist chamber

How to do it

A few old margarine tubs or other old food containers are perfect for this, clean them first and please don’t use them for food again afterwards. Fold up a sheet of kitchen towel and put it in the bottom of the tub, give it a good soaking of tap water and pour out all the excess liquid. Go outside and have a look around, try to find bits of twigs, leaves and things that have gone a little bit rotten already and put one or two small pieces in each tub, try to avoid picking up little critters like woodlice and earwigs – they’ll be happier outside. Put the lids on the tubs and bring them indoors. Now wash your hands!

Keep them in the dark, room temperature is fine. Every few days have a look. You might see thin tendrils crawling across bits of wood or on the kitchen towel, they might be bright yellow, they might be beige but they’re slime moulds!

They’re nearly impossible to identify when they’re in the crawling around stage, it’s the tiny mushroom like fruiting bodies you need for that. You could try leaving one in the light for a few days and see if it makes spores.

When you’re finished, put the leftovers on the compost or in the bin, wash your tubs and reuse or recycle them.

Why not take some photographs and send them in We’d love to know how you get on!

You can email us here – i.j.portman@warwick.ac.uk

So, if you fancy a career in fungi, and are of university age … you know where to apply!

Geastrum triplex, Collared Earthstar fungus
An earth star fungus. One grew in a pot by my back door a couple of years back.

www,nwhwildlife.org has 100 advert-free articles available for you. Free education.

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