DGGE community fingerprints of the consortia supported by the seven-stage reactor system studied. Individual lanes contain 16S rDNA PCR products from total DNA extracts. Lane 1, TBR1; lane 2, TBR2; lane 3, TBR3; lane 4, TBR4; lane 5, MLE1; lane 6, MLE2; lane 7, MLE3.