Here is some jar culture of Pleurotus ostreatus. This is an easy mushroom to grow. In fact, this batch got contaminated with green mold, but miraculously recovered and mycelium completely dominated the substrate afterword.
This gives me a clue about contamination and succession of mushroom mycelium. Natural environment is more complex array of microorganisms and potentially contaminating ones, but as long as the growing condition shifts to what's more desired by mushrooms, then the previous contaminant organisms just give their place to succeeding mushroom.
In this case, easy sugar and starch got consumed by green mold and some bacteria, but once they are consumed, it no longer needed to be there and mushroom that can decompose more complex fiber and lignin was called for.
This condition also applies to gardens and farm fields. If we can keep the field clean or get the field cleaned by some organisms, then beneficial fungi can start growing, which in turn create nutrient cycle without fertilizers and potentially harmful side effect like pest and disease problems.
Often times, where I find mushrooms growing in tea fields and vegetable fields is barely disturbed by pests and diseases. The soil drainage is so good that right after heavy rain, it already feels dry to touch. Also, it keeps the soil dry in moist environment and keeps certain pest problems like mildew and fungal infection minimal. Though I haven't grown any tomatoes or cucumbers in recent years, I can't tell if this works as good as it should, since I don't mind not having tomatoes and cucumbers in my diet much, but we got some seedlings of cucumbers this year so we'll see how it goes.
