DNA in a denaturing gradient gel electrophoresis (DGGE) band that could not be sequenced after recovery from the gel was cloned into a TA cloning vector and a library was constructed and then 13 clones randomly picked up from the library was sequenced. Although the excised DNA from the DGGE gel showed a single band, the library consisted of several different sequences phylogenetically. This phenomenon was also observed in several other DGGE bands. Therefore, this suggests that a single DGGE band does not always represent a single bacterial strain and a new bias for quantitative analyses based on band intensities has been identified.