What's this bright yellow goo?

[kris2001]

I pried open a small piece of rock attached to a plate this is where with my mushroom was sitting....

I found this yellow gooey thing under the rock is it bacterial or is it some sort of a sponge? I believe it's bacterial it is very yellow though very sticky!

 

[AcroNem]

At first glance I'd say it's a sponge, harmless.

 

[BAUCE]

yeah those are sponges