Experimental Soft Condensed Matter Group Harvard University, Prof. D. A. Weitz Cool Picture of the Moment

Many species of bacteria are known to excrete surfactants. It is widely believed that the physical role of these surfactants is to lubricate surfaces so that bacteria can slide around. However, a more directed type of motion could be generated if surfactant gradients were produced in bacterial colonies. To explore this possibility, we study Bacillus Subtilis biofilms grown as pellicles at fluid-air interfaces. We find that the biofilms rapidly climb the walls of their vessel, and that this kind of wall climbing requires the production of surfactant, but does not require flagellar motility. Furthermore, the nutrient medium surface tension changes in direct proportion to biofilm climbing height. This movie is an example of a Bacillus Subtilis pellicle biofilm climbing the walls of a martini glass over the course of approximately 8 hours.

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