Gellan gum is my preferred gelling agent for spore germination. Why?
Softer than agar - the media tends to be easier to streak spores from swabs.
Water Retention - This media type will remain moist for more extended periods. This allows slower germinating spores to finish germinating without the media drying up.
Optically clear - this allows you to see if any bacteria or competitors are growing on either side of the 2D plane of growth.
Look closely at the photo above. You will be able to see bacterial colonies growing from a dirty swab. On the far left side, you may spot some bacteria being covered by mycelium. The covered contaminants will be easy to spot from the other side.
Here is the recipe I use when without my t.o.c. premix, however, I recommend using the Tip of the Cap gellan gum for best growth results. Note: (Gellan gum needs additives to allow it to gel properly. For the most reliable results buying the gellan gum from Tip of the Cap mushrooms will help ensure proper gelling strength as it already has the correct ratios of additives present.)
- Makes about 30 - 40 plates depending on depth of pour.
- 1 liter of water
- 25g sorghum syrup or dextrose
- 4g potato infusion, or 2g yeast extract ( granular yeast or peptones will make the media less optically clear.)
- 10g gellan gum
Let’s make some gellan gum media for germinating spores. I will make 4 different media in 250 ml bottles for this demonstration.
- Bottle 1 - HSYG - High Nutrient Sorghum Syrup Yeast Gellan
- 7.5 grams sorghum syrup
- 0.25 grams yeast
- 3 grams gellan gum
- 250 ml water
- Bottle 2 - HSG - High Nutrient Sorghum Syrup Gellan
- 7.5 grams sorghum syrup
- 3 grams gellan gum
- 250 ml water
- Bottle 3 - HSRbG - High Nutrient Sorghum Syrup Rose Bengal Gellan
- 7.5 grams sorghum syrup
- 3 grams gellan gum
- 250 ml water
- 0.0125 grams rose bengal
- Bottle 4 - LSG - Low Nutrient Sorghum Syrup Gellan
- 3.5 grams sorghum syrup
- 3 grams gellan gum
- 250 ml water
Now I place my stir bars in the jars and mix until homogenized. You want to make sure there is nothing stuck to the bottom.
After making my media and tightening my lid on the media bottles(a quarter turn from finger tight), I place them into the autoclave. Allow the autoclave to heat sterilize media at 15psi for 15 - 20 mins at a low rock. Try not to let the rocker rock too hard as you don’t want to burn the sugars or nutrients.
After sterilizing, place the autoclave in front of the flow hood or a clean space and cool enough to handle it safely. Allow your media bottles to cool down to about 140F (for gellan gum) or 120F for agar before pouring your plates.
Allow poured plates to cool down for a total of 24 hours in front of the flow hood to get rid of all the condensation.
Here is a demonstration of streaking plates and some other methods of plating spores. Try multiple ways and see which one you think works best for you!