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BlindMyce
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Registered: 06/02/23
Posts: 24
Last seen: 2 months, 28 days
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Publication about effects of agar concentration on fungal hyphal systems morphology 1
#28435241 - 08/15/23 06:04 PM (5 months, 10 days ago) |
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Not sure if this publication has been discussed here (or posted here) but I searched and couldn't find anything related to it.
It's a study looking at the effects of differing agar concentrations on the morphology of mycelium. They used P. populinus but it seems likely that the results would translate similarly to pretty much all species discussed here on the site.
For those allergic to reading (and the TL:DR crowd), the following two figures I pulled and post below capture the gist of the paper quite well (eg. increased agar concentration resulted in what many would call "more robust rhizomorphic growth").
They went up to 6% agar, I have attempted higher agar percentages myself in the past (up to ~5%) with an undesired amount of darkness/sediment being the result but i was also varying other components at the time so it may not have been attributable to the increased agar. I would expect the pour-ability properties be a bit different at lower threshold temps compared to the usual (around here) 2% agar.
Anyways... feel free to discuss, reproduce, test.
Edited by BlindMyce (08/15/23 06:08 PM)
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covertjoy

Registered: 07/09/23
Posts: 272
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Re: Publication about effects of agar concentration on fungal hyphal systems morphology [Re: BlindMyce]
#28435634 - 08/16/23 01:17 AM (5 months, 9 days ago) |
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Thanks for sharing. I wonder what a similar study but for spore germination would be. Perhaps lower agar % would be preferable for germination then higher agar % for subsequent transfers.
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covertjoy

Registered: 07/09/23
Posts: 272
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Re: Publication about effects of agar concentration on fungal hyphal systems morphology [Re: BlindMyce]
#28436281 - 08/16/23 04:58 PM (5 months, 9 days ago) |
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My understanding of rhizomorphic growth is that it is a form the mycelium takes in order to spread and search for nutrients. Tomatose growth is the form it takes when it has found the nutrients and is consuming them as efficiently as possible.
So it makes sense that higher % agar would result in better rhizomorphic growth since the mycelium is less able to penetrate the agar, meaning that A) it will have access to less nutrients per area and therefore more likely to form rhizomorphicly to search out better nutrient stores and B) it will grow more laterally simply because there is more of a resistance delta growing into the agar.
It also makes sense that a mycelium growing rhizomorphicly would fruit more readily (as anecdotal evidence suggests) since fruiting and releasing spores is another way for the organism to spread in the search for more nutrient rich locations to colonise. This is feasible since it is observed that if the mycelium is not happy in its current location due to bacterial contamiation it can choose to fruit in order to spread to somewhere else.
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BlindMyce
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Registered: 06/02/23
Posts: 24
Last seen: 2 months, 28 days
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Re: Publication about effects of agar concentration on fungal hyphal systems morphology [Re: covertjoy]
#28436605 - 08/16/23 10:40 PM (5 months, 8 days ago) |
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Quote:
covertjoy said: My understanding of rhizomorphic growth is that it is a form the mycelium takes in order to spread and search for nutrients. Tomatose growth is the form it takes when it has found the nutrients and is consuming them as efficiently as possible.
So it makes sense that higher % agar would result in better rhizomorphic growth since the mycelium is less able to penetrate the agar, meaning that A) it will have access to less nutrients per area and therefore more likely to form rhizomorphicly to search out better nutrient stores and B) it will grow more laterally simply because there is more of a resistance delta growing into the agar.
It also makes sense that a mycelium growing rhizomorphicly would fruit more readily (as anecdotal evidence suggests) since fruiting and releasing spores is another way for the organism to spread in the search for more nutrient rich locations to colonise. This is feasible since it is observed that if the mycelium is not happy in its current location due to bacterial contamiation it can choose to fruit in order to spread to somewhere else.
Interestingly/ironically, is that agar is traditionally and to my knowledge, universally used, as a strictly 2D planar growth culture media. The entire history of agar use has been based on the idea that things grow on the surface. There are other more recent substrates used in 3D cell/organoid/tissue culture. Various gels that are molded or printed in the same manner as plastic (I have a biological gel printer of this type in a lab just down the hall). That being said, I have certainly observed mycelial growth that appears to "eat" into the Z axis of agar. It's difficult to say by how much it is going in that direction. Nevertheless, given the lifespan of a 90mm Petri dish, I think the planar 2D surface model is really the only one worth considering. I suppose that's a long way of saying that I think the human intuition that "a firmer surface causes more robust lateral growth because it can't grow down into the media as well " is likely an oversimplification of the system being modeled and also missing the true cause/effect relationship. Agar, no matter the percentage, has always been about a strictly 2D surface in terms of growth on dishes. The only times I've ever read any mention of growth in other directions is with preservation of samples on slants (which obviously consume the growth media over very long periods of time).
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covertjoy

Registered: 07/09/23
Posts: 272
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Re: Publication about effects of agar concentration on fungal hyphal systems morphology [Re: BlindMyce]
#28436664 - 08/17/23 01:24 AM (5 months, 8 days ago) |
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Quote:
BlindMyce said: Interestingly/ironically, is that agar is traditionally and to my knowledge, universally used, as a strictly 2D planar growth culture media. The entire history of agar use has been based on the idea that things grow on the surface. There are other more recent substrates used in 3D cell/organoid/tissue culture. Various gels that are molded or printed in the same manner as plastic (I have a biological gel printer of this type in a lab just down the hall). That being said, I have certainly observed mycelial growth that appears to "eat" into the Z axis of agar. It's difficult to say by how much it is going in that direction. Nevertheless, given the lifespan of a 90mm Petri dish, I think the planar 2D surface model is really the only one worth considering. I suppose that's a long way of saying that I think the human intuition that "a firmer surface causes more robust lateral growth because it can't grow down into the media as well " is likely an oversimplification of the system being modeled and also missing the true cause/effect relationship. Agar, no matter the percentage, has always been about a strictly 2D surface in terms of growth on dishes. The only times I've ever read any mention of growth in other directions is with preservation of samples on slants (which obviously consume the growth media over very long periods of time).
Here is a quote from Chapter 1 of Ecology of Saprotrophic Basidiomycetes:
Quote:
The three-dimensional shape of the mycelial boundary is largely governed by the anatomy of the resource and by surrounding antagonistic fungi. For example, in wood, decay columns tend to be larger longitudinally than in other directions, reflecting difficulty of radial and tangential spreads. The diamond shaped cankers on sycamore (Acer pseudoplatanus) caused by Gibberella Zeae (Ascomycota) result from spread between nutrient rich ray cells (Bevercombe and Rayner, 1980).
And link for reading: https://www.google.co.uk/books/edition/Ecology_of_Saprotrophic_Basidiomycetes/3dGf9vUIlCIC?hl=en&gbpv=1&dq=Ecology+of+Saprotrophic+Basidiomycetes&printsec=frontcover
I can't confirm it personally but I have read on here about someone flipping the agar and taking transfer from the underside, after it had spread through the z-axis (link). Mycelium can spread through wood, it is not unrealistic to think that it is able to make it's way through agar.
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