No abstract

Two-dimensional polyacrylamide gel electrophoresis was used to demonstrate phenotypic differences between Pseudomonas aeruginosa biofilm cells and the planktonic counterpart cells under defined culture conditions. Glass wool was used as a substratum for cell attachment as it affords a large surface-to-volume ratio (1 g with a mean diameter of 15 microns = 1300 cm2), supports the growth of biofilms, allows for free movement of cells between the inter-strand spaces, and it facilitates the exchange of nutrients and oxygen. It also allows for the separation of the biofilm biomass from the surrounding surface influenced planktonic (SIP) cells for further characterization. Comparative analysis of the respective proteomes indicated striking differences in the protein patterns of planktonic, biofilm and SIP cells. We selected 41 proteins, the levels of which varied in a significant and reproducible way in the respective protein profiles. In the biofilm cells, a general up-regulation of the spots was seen, but in SIP cells expression of these spots were generally down-regulated. Altogether six unique proteins were seen in the planktonic cells, while the biofilm and SIP cells contained five and two unique proteins, respectively. Glass wool, therefore, appears to be an ideal attachment surface for the study of biofilm development.

No abstract

Two-dimensional polyacrylamide gel electrophoresis was used to demonstrate phenotypic differences between Pseudomonas aeruginosa biofilm cells and the planktonic counterpart cells under defined culture conditions. Glass wool was used as a substratum for cell attachment as it affords a large surface-to-volume ratio (1 g with a mean diameter of 15 microns = 1300 cm2), supports the growth of biofilms, allows for free movement of cells between the inter-strand spaces, and it facilitates the exchange of nutrients and oxygen. It also allows for the separation of the biofilm biomass from the surrounding surface influenced planktonic (SIP) cells for further characterization. Comparative analysis of the respective proteomes indicated striking differences in the protein patterns of planktonic, biofilm and SIP cells. We selected 41 proteins, the levels of which varied in a significant and reproducible way in the respective protein profiles. In the biofilm cells, a general up-regulation of the spots was seen, but in SIP cells expression of these spots were generally down-regulated. Altogether six unique proteins were seen in the planktonic cells, while the biofilm and SIP cells contained five and two unique proteins, respectively. Glass wool, therefore, appears to be an ideal attachment surface for the study of biofilm development.

respectively. An open recirculating cooling water system feeding a modi®ed Robbin's Device with synthetic cooling water to simulate the environment of an industrial cooling water system was set up. Planktonic and bio®lm (mild steel and Nylon 1 ) samples were taken weekly in 1997 (196-d period) and fortnightly in 1998 (252-d period). Each bio®lm was scraped off and diluted in 10-ml 1 Â phosphate-buffered saline (PBS). Serial dilutions were performed and plated onto R2A agar (pH 8Á0) to obtain the predominant culturable bacteria. The diversity was determined by allocating groups according to colony morphology, diameter and colour. Diversity was calculated according to the Shannon± Weaver Index. During the ®rst run (1997), dispersant was added on day 57 to a ®nal concentration of 15 mg l À1 for 49 d, stopped for 49 d and dosed at 30 mg l À1 for 41 d. The second run entailed adding dispersant to a ®nal concentration of 30 mg l À1 on day 98 for 70 d, stopping dosing for 56 d and resuming dosing at 30 mg l À1 for another 28 d. The 2-year evaluation period demonstrated that the bio®lm-removing action of the dispersant decreased to a point where it was not effective at all. Our results showed that the synthetic dispersant evaluated was only effective initially, but was ineffective in controlling biofouling on Nylon 1 , and to a lesser degree on mild steel at the recommended (15 mg l À1 ) as well as at double the recommended concentration in the long term. The release of cells from bio®lms observed when dispersant dosing was terminated, supports the notion that a community attaching in the presence of the surface active agent was selected for. The decreased ef®cacy may therefore be due to a selection of strains able to remain attached and/or attach in the presence of the dispersant as demonstrated by shifts in the bio®lm communities on both Nylon 1 and mild steel.