Biofilms are usually formed by different microbial species: bacteria, fungi, algae, etc. They grow on surfaces that support their adherence (porous, scratched or coarse surfaces) or that have been improperly cleaned and disinfected. Biofilm formation on surfaces usually follows a sequential process initiated by adhesion of cells to the surface. This process is represented in the Figure above.
Microcolonies are formed after initial adhesion, inducing phenotypic changes in aggregated cells so that they start producing polymeric substances that form the biofilm structure. Mature biofilms show a complex structure which grows perpendicular to the surface, usually shaped like a mushroom and containing channels that allow water circulation.
More information in: Componentes y funciones de la matriz de los biofilms bacterianos