What is biofilm made of?

Biofilm is a combination of microorganisms in multiple layers

The top layer of the biofilm is like “Park Avenue.” This is the layer that sees all the oxygen and gets all the food that floats by in the water. Because these microbes are fat and happy, they’re the breeders. They continuously spew individual microbes out like a volcano, seeding the water with microbes to float off and establish biofilms elsewhere.

The middle layer is the most mysterious layer of a biofilm. Recent studies suggest that the microbes in this layer are in a sort of suspended animation. If anything happens to the lower level, they come out of stasis and start behaving like the “slum-dwellers,” working on keeping the biofilm anchored to the surface. If anything happens to the “Park Avenue” microbes, they’ll start acting like those, living the high life and spewing out microbes. It’s because these microbes are normally in “suspended animation” that makes biofilms so tough to kill/remove. Their existence in the middle layer of the biofilm shields them from the sanitizer in the water. 

These three different layers, along with the protective slime that houses them, provide a defense mechanism for the microorganisms. It allows them to survive should anything happen to any of the layers.