Shrooms and sterility

Does anyone know why captive fungi and myxomycetes tend to need sterile or nearsterile conditions, but not in the wild? I’ve not been able to find satisfactory answers by googling.

Even coprophilous taxa, which undoubtedly encounter a very large number of microscopics in the wild, seem to often need sterility. I’ve seen more than one research paper mentioning, ahem, autoclaved dung agar.

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In the wild there is constant competition with other organisms. Different species will win out in different circumstances depending on the exact conditions. The result is that overall, any species will find a niche to survive and reproduce (or would be extinct). But when we want to cultivate particular species, we have to eliminate all that competition to guarantee that only our chosen species will survive in our particular conditions.

If you just wanted to cultivate a mushroom, any mushroom - you wouldn’t need to create sterile conditions. You could just create a fungus-friendly environment and see who popped up. That’s all that happens in the wild.

You could think of it the same way as keeping animals in captivity. In the wild, rabbits are able to find places with enough food and shelter to breed and survive. But if you want to keep rabbits in your garden then you have to eliminate the competition and predators to ensure that your particular conditions are favourable for the particular species you want to prioritise.

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I suppose that your question just reflects how little we know about the functioning of Nature. First thing: competition. We know a little bit about it: fungi compete and even eat each other. But there is a part we know almost nothing about: co-existence and symbiotic relationships between fungi and other organisms. Fungi not only compete. They need each other and each others‘ chemicals, also other microorganisms to co-exist, to succeed on the substrate while it ages. For example, some bracket fungi can only grow after other brackets have done their job in deteriorating wood. There is plenty of this in nature, but when we take the substrate out of the nature, the co-existence, the succession chain is broken and the most aggressive and least demanding competitors emerge.

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I’m just speculating, but I think such sterile substrates may be advised because most captive mushrooms are grown for human consumption. Most people are squeamish about eating dirt and whatever bacterial (et.al.) load may be in it.

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Sorry, but no. Sterile substrates are required for any fungi to grow axenic (pure) culture. For research, too, which is not known to be squeamish :-) Even edible mushrooms are grown sterily only because on non-sterile substrates mushrooms would be soon overcome with mould and pathogenic fungi which will mean serious decrease in production.

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Really nice, clear explanation. We sometimes forget that everything we look at in nature is shaped by competition, and that extends to organisms we wish to selectively cultivate or keep captive as well.

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I think I’ve not worded my question well.

To rephrase: why are captive angiosperms often much more skilled at defending themselves from competing taxa than captive fungi and myxomycetes?

Sure, you have to remove weeds that pop up in your houseplant’s pot, but houseplants are normally able to resist attack from numerous soil microbes in the dirt quite easily.

Also, have there been any attempts to create laboratory conditions that encourage antibiotic-nonproducing mushrooms’ resistance to competitors when unsterilized? I know certain fast-moving myxomycetes can reduce microbial load by migrating (this causes competitors to be sloughed off and physically ejected from the slime, not sure how slow myxos that don’t make antibiotics do it though), and that many lichens are sun-resistant and can cook unspecialized pathogens to death by being dry and hot, but cannot find any references mentioning the anticompetitive mechanisms of most saprotrophic fungi that don’t produce antibiotics.

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Theoretically, if you found a way to sterilize a plant without killing it - that is, remove all the microorganisms that aid its life, and plant it into a soil with limited nutrients and no microorganisms that will aid the plant, it will soon die, too. But the thing is that plants can “catch” the aiding organisms from environment or carry them. Actually, we, Homo sapiens would die very soon if all our symbiotic microorganisms were removed. The thing is, that fungi probably have more limited range of aiding microorganisms (of which we know almost nothing) and therefore are more succeptible to the removal from nature.

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Небольшое дополнение. Ещё в ВУЗ-е, на парах по микробиологии, нам говорили, что далеко не все грибы растут на питательных средах. И это основательно затрудняет изучение микромицетов.

I’d agree that competition/interaction and metabolite production (not just antibiotics/antifungals) are key to this question, and most poorly understood. Any comparison with plants perhaps also needs to take into account relative size, diversity and abundance. The average plant will be competing with relatively few other plants potentially in the same ecological niche. The average fungus will be competing with thousands of competing fungal/bacterial species - in just a single teaspoon of soil. There are bound to be some competing species that have an advantage in any specific sample.
https://www.bbc.com/news/science-environment-53197650#:~:text=A%20teaspoon%20of%20soil%20from,starting%20to%20explore%2C%20say%20scientists.

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Yes, this is right: many species of fungi do not grow on media at all - sterile or not. That is why now species counts based solely on obtained cultures are not considered valid. Metagenomics should be used for that, though it also has its own pitfalls.

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Bravo for making me click on the bait and bravo to the fascinating insights here in response to such a good question.

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Bait?

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title innuendo… possibly unintentional.

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(pfffffffffffft y’all mammal primates clearly think way too much about dirty mammal replication techniques)

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Having near sterile growing conditions ensures that you grow the fungi you want, whereas Mother Nature doesn’t intend to grow specific fungi, they just grow because the conditions happen to be right for them.

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I can’t answer the “why do captive fungi and myxomycetes seems less capable of self-defense?” question, but I can speak about plants.

It may have to do with scale at older ages. A young plant honestly does quite poorly at defending itself from the world/competing organisms. In the horticultural trade, plants are often started in sterilized or sanitized* soil, and kept under very careful conditions. There is also a lot of fungicide, insecticide, and herbicide used (unfortunately and often unnecessarily, in my opinion). When you are buying your houseplant from a nursery/other retailer it is at a larger and later life stage and so has more internal resources to fight off a small amount of fungi or bacteria and might blow in on the wind, or in other ways, but its origins may have been as carefully crafted as a captive fungi’s little dish.

Additionally, such “adult” plants will still need to be kept in the right conditions: light, day/night cycle, temperature, humid vs dry air, soil moisture, nutrient levels, and so on for them to do well. Powdery mildew and rust infections happen frequently in my area. So does scale, aphids, and heck, even gophers, though we’re not talking about houseplants at that point. Depending on the plant species, powdery mildew can occur from as simple a reason as the leaves got wet, and the plant does not survive the resulting infection. Plants are genuinely pretty touchy and houseplants are specifically selected species known to be able to be grown in the conditions found in most homes. There are many plants that just won’t put up with those conditions, and need to be treated as carefully as if they were in a Petri dish.

Finally, sometimes plants are grown in sanitized soil* with additional specific organisms added into the soil as a beneficial partner to that plant. So while the plant is non-sterile, in a way people are putting in a lot of effort to ensure it has the absolute safest conditions for optimal health. More effort than just providing a plain sterile substrate, perhaps. So… I think plants aren’t as hardy as they first appear. Growers do a lot of work!

I hope my experience working in a native plant nursery was externally helpful for once! :)


*sanitized soil - what is that?

Where I worked soil was heated to about 140º, then held at that temperature for at least an hour. This tends to kill off the vast majority of detrimental microorganisms while leaving beneficial ones intact. I have no idea why beneficials seem to have this temperature cutoff, but it is a thing for sure! Here in California we specifically do it to prevent the spread of Phytophthora ramorum, the organism responsible for “SOD” or Sudden Oak Death, but it takes care of other disease causing organisms as well and allows us to recycle soil we already have on site. It’s wise to check if the nursery you’re buying from does this no matter where you live to help prevent “invasive microorganisms” and just to have healthy plants in general.

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While I can not give a technical answer on this subject, I refer you to this meme which discusses the same basic problem succinctly and humorously. (I have seen different versions of this meme floating around the internet).

https://memezila.com/wp-content/Plants-in-the-wild-vs-Plants-in-the-backyard-meme-5627.png

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