Affiliation of the sequences retrieved from the DGGE bands with existing 16S rRNA gene sequences, using neighbor-joining trees. Bootstrap values of below 50 are not indicated. The sequences from the database are indicated in italic with their accession numbers. The sequenced bands are shown in boldface. A, Fibrobacteres-Acidobacteria group; B, Cytophaga-Flexibacter-Bacteroides group; C, Betaproteobacteria; D, Deltaproteobacteria; E, Gammaproteobacteria.