A biofilm comprises any group of microorganisms in which cells stick to each other and often also to a surface.

These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPS).

The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA.

Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as “cities for microbes”.