BACTERIAL ADHESION UNDER STATIC AND DYNAMIC CONDITIONS

The deposition of various pseudomonads and coryneform bacteria with di fferent hydrophobicities (water contact angles) and negative cell surf ace charges on negatively charged Teflon and glass surfaces was invest igated. The levels of deposition varied between 5.0 x 10(4) and 1.6 x 10(7) cells cm-2 and between 5.0 x 10(4) and 3.6 x 10(7) Cells cm-2 fo r dynamic column and static batch systems, respectively, indicating th at there was a wide variation in physicochemical interactions. Batch a nd column results were compared in order to better distinguish between hydrodynamic and other system-dependent influences and method-indepen dent physicochemical interactions. Despite the shorter suspension-soli d contact time in columns (1 h) than in batch systems (4 h), the level of deposition (expressed as the number of cells that adhered) divided by the applied ambient cell concentration was 4.12 +/- 1.63 times hig her in columns than in batch systems for 15 of 22 strain-surface combi nations studied. This demonstrates that transport of microbial particl es from bulk liquid to surfaces is more efficient in dynamic columns ( transport dominated by convection and diffusion) than in static batch systems (transport by diffusion only). The relative constancy of this ratio for the 15 combinations shows that physicochemical interactions affect adhesion similarly in the two systems. The deviating deposition behavior of the other seven strain-surface combinations could be attr ibuted to method-dependent effects resulting from specific cell charac teristics (e.g., to the presence of capsular polymers, to an ability t o aggregate, to large cell sizes, or to a tendency to desorb after pas sage through an air-liquid interface).