Fungi have cell walls which - unlike those of plants, which are made out of cellulose, xylan, and lignin - are instead made out of chitin, glucan, and mannans.
A fungus I'm planning on writing about is intended to be symbiotic - specifically, it uses an animal as a host in exchange for surrounding said animal's bones with the silicified corpses of its own cells, reinforcing them against shear stress.
Wood silicifies when dissolved silica seeps into the lignin within the walls of the wood's cells. Fungal cell walls don't contain lignin. Still, I want this fungus's cell walls to silicify. Via what biochemical processes can this occur?
Don't concern yourself with how this fungus came to be (evolved naturally, artificially created, etc.); all I care about is the biochemistry behind it being sound.