The effect of flow direction and magnitude on the initial distribution of Pseudomonas aeruginosa cells attached to glass

Abstract

The effect of flowrate and Reynolds Number, Re, on the spatial distribution of individual Pseudomonas aeruginosa cells during their initial attachment to glass flowcells was observed in a series of time-lapse images obtained over a 56-h period. It was shown that flow affected the distribution at Re > 245. Under laminar flow conditions, Re = 96, the distribution of bacterial cells in 200 sub-areas was accurately predicted by using the Poisson distribution and was not dependent on the orientation or shape of the sub-areas. Under turbulent flow conditions, Re = 2220, cells initially attached in streaks along the line of flow. As bacterial cells accumulated on the surface, the streaks broadened and the distribution became more uniform. Analyses showed that, initially, flow had an effect on cell distribution in the flowcell with Re = 245, with significantly greater effects at higher Re. As the cell surface densities increased, the effect of flow direction on cell distribution decreased. It is concluded that the visco-elastic properties of the extracellular polymeric substances (EPS) in which the cells are embedded, significantly affect the distribution of attaching cells.

Keywords:

• Biofilm
• initial events
• surface distribution
• effect of flowrate

Acknowledgements

Our thanks to Dr Marie Lewis for help during the work and for allowing us to include data on doubling time and cell densities for the P. aeruginosa cultures.