Biofilm composed of Pseudomonas aeruginosa, Pseudomonas fluorescence, Klebsiella pneumoniae and Stenatrophomonas maltophilia grown in a glass flow cell in turbulent flow. The average liquid flow velocity was 1 m/s (Reynolds number = 3,600). The outlined cell cluster (an aggregate of bacterial cells in a slime matrix) was moving downstream along the top wall of the flow cell at approximately 12µm per hour. Although this cluster is not going to get ticketed for speeding, we have estimated that such migration occurring in ripples and clusters on all surfaces of the flow cell may result in a net downstream flux of 1000's of cells per cm per hour. The cell cluster has been outlined so it can be distinguished from the thin basal layer of bacterial cells (sometimes termed the base biofilm). To see a movie sequence click on the image (Windows Media Player works well). Frames were captured at 20 min. intervals over a period of 2 hours.

Stoodley, P., Hall-Stoodley, L., Boyle, J.D., Jørgensen, F. and Lappin-Scott, H.M. 2000. Environmental and genetic factors influencing biofilm structure. In Community Structure and Cooperation in Biofilms. pp. 53-64. (eds. D. Allison, P. Gilbert, H.M. Lappin-Scott and M. Wilson). SGM Symposium Series 59. Cambridge University Press, Cambridge. 

Stoodley, P., deBeer, D., Boyle, J.D., and Lappin-Scott, H.M. 1999. Evolving perspectives of biofilm structure. Biofouling 14:75-94.