The Biofilm World: What and How

Biofilms are sessile communities of microbes encased in a polymeric matrix, and their formation is a dynamic and cyclical process, conventionally divided into distinct stages, as reported in Figure above[i].

The above figure shows the different steps of the biofilm formation process represented by false-colored scanning electron microscope (SEM) images of Staphylococcus aureus ATCC 25923 biofilm grown on glass. The initial phase of biofilm formation consists of adhesion to an abiotic/biotic surface. Bacteria release exopolysaccharides matrix (light red) and communicate by means of signal molecules, thanks to which the irreversible adhesion can take place.

Finally, they organize mature structures. These have a complex spatial organization, can contain distinctive features, such as water channels, and can include multispecies consortia (not shown in the image). In a process called detachment, biofilm expansion can also occur with the release of planktonic cells, which in turn can colonize other surfaces. For clarity, this cartoon shows an exemplified matrix in light red, although in SEM images its presence is underestimated due to sample preparation, dehydration, and instrumental limits [ii,iii].