Figure 1. Capillary test for demonstration of chemotaxis. (a) Bacteria are equally distributed in a flat vessel. (b) An aspartate solution is added through a capillary. Within a few minutes, all of the bacteria present in the vessel have gathered around the tip of the capillary, with some even swimming into the capillary. (Drawing: Anne Kemmling, Goettingen, Germany.)

Figure 2. Bioluminescent bacteria on a Petri dish. The organisms (Vibrio fischeri) were grown on a saline complex medium. The photo was taken in complete darkness; exposure time: 15 seconds. (Photograph: Anne Kemmling, Goettingen, Germany.)

Figure 3. Examples for subaerial (left) and subaquatic (right) biofilms. (Photograph: Anne Kemmling, Goettingen, Germany.)