Bacteria and Archaea profiles by PCR-DGGE. DNA was extracted from reactor biofilm samples. 16S rRNA gene sequences were PCR amplified with primers specific for Bacteria or Archaea, and PCR products were transferred onto a 20 to 70% urea-formamide DGGE gel. (A) Bacteria. Lanes: 1 and 9, original granular sludge; 2 to 8, biofilm samples taken after 7, 14, 35, 56, 81, 116, and 180 days of operation, respectively. Lanes 7 to 9 are from another DGGE gel and were adjusted on the basis of the profiles of the original sludge. (B) Archaea. Lane 1, original granular sludge; lanes 2 to 5, biofilm samples taken after 7, 14, 56, and 81 days of operation, respectively.