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Center for Biofilm Engineering
Movie Description:
Biofilm ripples traveling downstream in a glass tube
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| Time lapse imaging showing a 14 day biofilm traveling
along the (upper) wall a glass tube flow cell. The biofilm, which was
composed of P. aeruginosa, P. fluorescens, K.
pneumoniae, and S. maltophilia, was grown at a fluid
velocity of 1 m/s. The ripple migration velocity and morphology were a
function of the velocity of the liquid in the tube (Stoodley et al.
1999a). The ripple beds were traveling downstream at approximately 20
microns/h. Although the velocity is very low it may represent a large
downstream flux of micro-organisms. For example a biofilm containing a
typical surface concentration of 1x106 bacterial cells (by CFU)/cm2
moving at 20 microns /h in a 1 cm diameter pipe would represent a flux
of over 6,000 organisms per cm every hour. The fluid like flow of the
biofilm may be explained by the discovery that these biofilms were
viscoelastic and could flow when a yield fluid shear stress was
exceeded (Stoodley et al. 1999b). Surface colonization by flowing
biofilms may be significant in the dissemination of contamination both
in public health and in industrial fouling. Usually it is assumed that
biofilms colonize solid surfaces by the transfer of suspended cells
from a liquid to the surface. Since biofilms are often more resistant
to antibiotics and biocides than suspended cells the transport of
biofilm along surfaces will, presumably, allow biofilms to colonize
surfaces without requiring the more susceptible suspended phase. The
movie was taken over a 12 hour period. Scale bar = 100 microns.
Movie Author: P. Stoodley
Supplemental Online Material:
Stoodley, P., Lewandowski, Z., Boyle, J.D. and Lappin-Scott, H.M.
1999. The formation of
migratory ripples in a mixed species bacterial biofilm growing in
turbulent flow. Environ. Microbiol. 1:447-457.
Further Reading:
Stoodley, P., deBeer, D., Boyle, J.D., and Lappin-Scott, H.M. 1999.
Evolving perspectives of
biofilm structure. Biofouling 14:75-94.
Purevdorj, B., Costerton, J.W., and Stoodley, P. 2002.
Influence of hydrodynamics and cell signaling on the structure and
behavior of Pseudomonas aeruginosa biofilms. Appl. Environ.
Microbiol. 68(9):4457-4464. |
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Biofilm ripples moving along glass surface
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| 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 ripples were moving
downstream along the top wall of the flow cell at approximately
20µm per hour. Notice how the ripples flowed around the cell
cluster indicated by the open arrow. It is not clear why this
cluster was more firmly anchored to the surface than some of the
other biofilm structures. In the bottom right corner of the
image, cell clusters can also be seen moving downstream. The
fluid-like behavior of the biofilm may be explained by its
material properties. Using a non-destructive, in situ method, we
demonstrated that the biofilm had similar properties to those of
a Bingham liquid. At low shear stress the biofilm behaved
elastically, but at higher fluid shear stresses, when the yield
stress was exceeded, the biofilm began to flow like a viscous
liquid. To see a movie sequence click on the image (Windows
Media Player works well). Frames were captured at 15 min.
intervals over a period of 4.5 hours.
Movie Author: P. Stoodley |
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| Further Reading:
Stoodley, P., Lewandowski, Z., Boyle, J.D. and Lappin-Scott, H.M.
1999. The formation of
migratory ripples in a mixed species bacterial biofilm growing in
turbulent flow. Environ. Microbiol. 1:447-457.
Stoodley, P., Lewandowski, Z., Boyle, J.D., and Lappin-Scott, H.M.
1999. Structural
deformation of bacterial biofilms caused by short term fluctuations in
flow velocity: an in-situ demonstration of biofilm viscoelasticity.
Biotech. Bioeng. 65:83-92.
Purevdorj, B., Costerton, J.W., and Stoodley, P. 2002.
Influence of hydrodynamics and cell signaling on the structure and
behavior of Pseudomonas aeruginosa biofilms. Appl. Environ.
Microbiol. 68(9):4457-4464.
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