Is petri dish which is watery from condensation still viable?

I had been keeping a petri dish of oyster mushroom (Edeka) in the fridge for a while. When I took it out to use it today, I saw the condensation had formed into some water that was pooled on the surface of the mycelium around the edges of the dish.

Do you think the mycelium is likely still viable? Or would the water have drowned it? I tried putting a few slices of it in grain jars today too so will also find out first-hand


When i had too much liquid in my plates. I brought them back into my SAB, opened my petri and drained the liquid off. You may have to take the condensed side and flip it around so gravity helps drain it off. In this case you may be able to wipe it off with a clean swab.

Right now I don’t see any discoloration so you probably still good to use it. I would maybe make a new transfer of that into a new agar plate and see what runs out from that one, that way you will know for sure if it’s good or not.

This is from Glyph who answered a similar question Of mine, that you have…

“Don’t worry about the condensation. It’s a bit of a bother (not being able to see the agar and mycelium clearly) but it won’t cause any major issues, unless you’re getting so much condensation that it’s forming large water droplets. I generally store plates upside-down if they’re going to be in storage for a while (weeks or months). That ensures that no water drops or puddles end up on the surface of the agar.

One trick is to stack the plates on top of one another right after you pour them and before you wrap them in tape. You can also add a cup of hot water to the top of the stack. This seems to reduce the amount of condensation in each plate.“ - Glyph


thanks I’d missed that one! I’ll try the plates upside-down next time.

I also recently heard another approach for long-term storage that I want to try (from @MalteLarsen from @phylanx),

to cut a small piece of myceliated agar, and put it into a test-tube with distilled water for long-term storage in the fridge. apparently you can later take it out and put it onto agar and the mycelium will revive.

I’m curious to research this a bit, and find out how long mycelium can live like this. And what are other approaches for long-term storage and culture libraries.

I really like the idea of a distributed culture library, of people keeping and sharing cultures.

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Sharing some text from the Mycelium Preservation section of Radical Mycology (page 284):

Sterile Distilled Water

Here, mycelium is placed into small jars or 20-milliliter scintillation tubes that have been filled to their brim with distilled water and sterilized. In the absence of air, nutrients, and minerals, the mycelium will go into a state of suspended animation. These jars can then be sealed and stored at room temperature for years, and potentially decades, without any notable loss in mycelial vigor*. This simple, yet incredibly resilient means for preserving cultures was once commonly used in the mushroom cultivation industry. Unfortunately, it has not been well promoted in recent years.

First the mycelium is cultivated on a nutrified agar plate as normal. Once healthy and contaminant-free growth is seen, a piece of leading edge mycelium is then moved to a petri dish filled with distilled water agar (DWA) using a Plate-to-Plate Transfer. Once the mycelium begins to run on the water agar, several pieces of myceliated DWA are moved to a scintillation tube filled with sterile distilled water in the transfer space. The tube’s lid is then tightly screwed on and a double layer of plastic wrap is applied. The tube is labeled with date and species, then set on a shelf where it will not be disturbed.

* - The reference given here is the following paper:

Richter, D. L. (2008). Revival of saprotrophic and mycorrhizal basidiomycete cultures after 20 years in cold storage in sterile water. Canadian journal of microbiology, 54(8), 595-599.

An updated version of the paper from 2018 (30 years of cold storage) is available here (PDF).

Distilled Water Agar (DWA) Recipe

500 ml distilled water + 10 g agar agar

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so cool how simple this is and how long it can last!

@MalteLarsen also pointed out that keeping cultures in these water-tubes could be a really good/easy way to distribute them for a culture library. If you have a library of test-tubes with DWA and mycelium, could easily give these to friends.