How biofilms form

While bacterial cells tend to be rather solitary individuals, they are also known to form intricately structured communities called biofilms. But until now, no one has known the mechanisms that cause isolated bacteria to suddenly aggregate into a social network. New insights from the lab of HarvardMedicalSchool microbial geneticist Roberto Kolter reveal previously unknown communication pathways that cause such social phenomenon.

Using the non-pathogenic Bacillus subtilis as a model organism, Kolter and postdoctoral researcher Daniel Lopez discovered a group of natural, soil-based products that trigger communal behavior in bacteria. One molecule in particular, surfactin, is produced by B. subtilis. Biofilm formation begins when surfactin, and other similar molecules, cause bacteria to leak potassium. As potassium levels decline, a membrane protein on the bacterium stimulates a cascade of gene activity that signals neighboring cells to form a quorum. As a result, biofilms form.