Courtesy of: The Center for Biofilm Engineering, Montana State University

Step 1: Attachment

Free-floating microorganisms are attracted to dirty, wet surfaces and initially adhere to these surfaces using weak, van der Waals forces (intermolecular forces).  If not physically separated from the surface immediately, these microorganisms "permanently" attach to surfaces using cell adhesion molecules such as pili.  As the biofilm begins to form, more and more microorganisms are attracted to cell adhesion sites.

Step 2: Growth

Biofilm molecules, often consisting of many different species, communicate with one another using quorum sensing.  As the biofilm grows, the structure is held together and protected by an excreted EPS (extracellular polymeric substance).  The EPS protects the microorganisms living within and provides pathways for efficient communication between cells.  Microorganisms also undergo a genetic change when living within biofilms.  Several studies suggest that some cells such as E. coli become virtually immune to antibiotics due to a low level of metabolic activity.  Stewart and Costerton have estimated in a 2001 study that antibiotic resistance of sessile bacteria (living within biofilms) can be 1000 fold greater than that of planktonic bacteria (free-floating).

Step 3: Detachment

As biofilms grow into large macroscopic three-dimensional structures, shear forces may cause large sections of the biofilm to detach - releasing millions of organisms.  Many recalls and product contamination issues are caused by biofilm detachment.

In order to prevent contamination, it is essential to remove the entire biofilm matrix!

Put your mouse over the image above to see the effect of Sterilex® EPA-registered products on the same surface. This is an actual scanning electron micrographs.