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The spatial distribution of copper was determined in Escherichia coli PHL628 biofilmsusing a scanning electrochemical microscope consisting of an ultramicroelectrode inconjunction with a piezoelectric micro-positioning system. Because of their lowconcentrations, dissolved copper species in the biofilm were determined usingvoltametric stripping at - 0.7 V (vs. Ag/AgCl). As the microelectrode was slowly movedtoward the biofilm, the position of the bulk solution-biofilm interface was identified froman abrupt change in current produced by 0.4 mM hydroxymethyl ferrocene that wasadded as a redox mediator. After a 2 hour exposure to 0.2 mM copper, Cu was located inthe upper region of the biofilm with a penetration depth less than 150 m. A one-dimensionaldiffusive transport model adequately described the spatial distribution ofcopper in the biofilm, but the Cu retardation factor in the biofilm was more than 3-foldlarger than that calculated from the isotherm for Cu binding to suspensions of E. coliPHL628 cells. The electrochemical technique in combination with model calculationsprovide direct evidence in support of the concept that retarding metal diffusion could bean important factor for survival of biofilm microorganisms. Includes 8 references, figures.

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Edition: Vol. - No. Published: 06/01/2006 Number of Pages: 7File Size: 1 file , 270 KB