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Mushroom Growing How to Spot Contamination
Contamination can appear in many different ways and forms!
The question is, where did it come from? How did this contamination make its way onto my media?
Here, we will unveil the possible pathways contaminants such as mold spores and bacteria enter into your grow space.
Agar Contamination
*Yeast colonies are circled in red, trichoderma mold in yellow.
Above you can see there are a couple of different types of contamination surrounding the agar plates. To name a few, in photo 1, you can see on the right-hand side there is a white, circular splotch. You can see this type of growth at the bottom of photo 2 as well. These are common traits of yeast colonies. The green growth appearing in photo 3 circled in yellow, are a mold, likely trichoderma.
How did these ‘tams get there? First, we must look at the pattern of the contamination- we see they’ve formed along the edges of the plates. In order to find the source of the contamination, you will need to undergo a trial and error process.
There is a large number of variables, however here are a few common sources of contamination:
The stack of sterile plates you opened and poured your agar into may have had micropunctures or a cut in the sleeve
You could be sealing the plates with the outside of the parafilm instead of the inside, sterile portion.
The parafilm should be wrapped well underneath the plate as well where there could be a small draft between the parafilm and plate.
Your parafilm could be old or stored improperly, allowing for it to crack easily under pressure. If fresh parafilm isn’t available to you, you can purchase some here from Fresh off the Cap
Your air or station could be too dirty. A remedy for this can be using an (SAB) still air box or scrubbing the air clean with your laminar flow hood by leaving it on for around 15 minutes depending on your room size. You can also purchase secondary HEPA air purifiers to help as well. Wipe down your lab with cleaners such as a bleach:water solution or peroxide. Be wise, wear a mask when using chemicals and NEVER mix chemicals.
Your flow hood or air conditioners could be blowing contaminates through micropunctures in the parafilm. An easy fix for this is to store your wrapped petri dishes in a ziplock bag to protect the plates from the outside air.
Your hands could be dirty! Be sure to wear gloves and clean your hands with 70% iso alcohol.
You could have splashed media on your flow hood which allowed the contaminants to grow on your filter.
To summarize, be sure your hands are clean, your lab is clean, wrap your plates well with the sterile side of the parafilm, test plates from multiple sterilized purchased petri dish sleeves, and store your plates in a ziplock bag to keep them safe.
We hope you gained some insight here today and can continue to be experimental! We will continue to add to this contamination page as time allows.
Mush love! <3
-Fresh off the Cap