Figure 1.

Diagram of biofilm development. The development of a biofilm can be divided into six stages: planktonic bacteria, reversible attachment, irreversible attachment, microcolony, macrocolony, and dispersion. Planktonic bacteria attach to the surface through random or active movement, and the initial attachment is unstable and reversible. Contact with the surface promotes the stable and irreversible attachment of bacteria by contact-dependent gene expression. As the planktonic bacteria continue to attach and the attached bacteria multiply, microcolonies and macrocolonies that have complex three-dimensional structures gradually form. During this process, a series of phenotypic changes occur in the compactly distributed bacteria, which make the biofilm produce new ways to adapt to the environment. The typical macrocolonies are mushroom-like protrusions that are interspersed with fluid-filled water channels. In addition, macrocolonies establish more suitable shapes to adapt better to the environment. For example, in an aquatic environment with high flow rates, a biofilm can be flat or streamlined to buffer the high fluid shear force. Finally, some bacteria detach from the microcolony and disperse into the planktonic state, which initiates another new cycle of biofilm formation. Adapted with permission from Xin et al. (2010).