FIG. 1.

How do bacteria control the transition from free-swimming planktonic cells to life in a multibacterial community? On the left is shown fluorescently labeled planktonic P. aeruginosa at ×1,400 magnification. Within a few days, these individual microbes can form the community pictured on the right. This top-down fluorescent image shows a mature 5-day-old biofilm grown in a flowing system at ×230 magnification. The macrocolonies shown here (white arrows) vary from ∼35 to more than 50 μm in height.