The composition of biofilm populations in drinking water will mainly depend on the nutrient availability and the temperature. The nutrients may originate either from the raw water or from the installation materials. To determine the effect of drinking water pipe materials on the composition of biofilm populations, biofilms grown on different materials (EPDM materials, PEXb, PEXc and copper) were analyzed by cloning (16S rDNA) and the community fingerprinting method denaturing gradient gel electrophoresis (DGGE). Additionally the long-term effect of mechanical cleaning and disinfection with chlorine dioxide (0.2 mg/l, 24h) on the biofilm populations was tested. The biofilm populations had high diversities on growth supporting materials like EPDM and comparatively low diversity on PEX. The biofilms were dominated by Proteobacteria and the composition of the subdivisions was influenced by the applied material. Flavobacteria and members of the family Sphingomonadaceae, which are known to degrade several organic compounds, were found on EPDM materials and might be suitable as indicators for hygienical relevant materials. Comparison of biofilms previously treated with disinfectants with untreated ones by DGGE revealed a considerable population shift depending on the pipe material.

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