Biofilm

A biofilm is any group of microorganisms which stick to cell surfaces.
These sticky cells create a slimy layer outside the cells of the body. The cells in the biofilm produce extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure they are a community lifestyle for microorganisms. They have been metaphorically described as "cities for microbes".
The biofilm bacteria can share nutrients and are sheltered from harmful factors in their local environment, such as desiccation, antibiotics, and the host's immune system. The film of bacteria which live on your teeth are an example. Biofilms also form on inorganic objects like stones in water.