Bacteria in a biofilm, illustration - stock illustration

Spherical bacteria and rod-shaped bacteria inside biofilm, illustration. A biofilm is a colony of bacteria that forms a coating on a surface. Common places for biofilms to develop are in the mouth, where they can cause tooth cavities and gum disease, on contact lenses, where they can cause eye infections, on rocks submerged in water, and on industrial equipment, where they can cause fouling.