Community profiles of merA amplicons from a technical scale biocatalyzer over 224 days of operation at a chloralkali factory. A, Silver-stained TGGE gel with DNA of separated mer A PCR products of biofilm samples. The numbers on the top of the lanes indicate the days since operation started. Bro12 indicates the merA PCR product amplified from genomic DNA of Ps. aeruginosa Bro12. Most inoculum strains (lane 1), disappeared and returned from time to time. The predominant signal at position (?) did not belong to any inoculum strain, but was identical to that of the invader Ps. aeruginosa Bro12. B, below is a schematic representation of the identified signals. Different colors represent different strains. C, at the bottom are the corresponding RISA results of the rrn-intergenic spacer region, displayed with a corresponding color code (N.A. = not analyzed).