DGGE profile of the enrichment cultures from a diluted pre-culture sample. (A) Degradation of 4-aminopyridine by the diluted enrichment culture. The enrichment culture grown in medium containing 4-aminopyridine was diluted 108-fold with 0.8% NaCl solution, and the diluted culture was used to inoculate fresh medium containing 2.13 mM 4-aminopyridine; the subculture was incubated at 30°C with shaking. The remaining 4-aminopyridine (4-AP) was measured using HPLC as described in the text. (Subcultures: a, open triangles; b, open circles; and c, filled squares; d, filled circles). The results of one representative experiment are shown; the residual 4-aminopyridine was measured in triplicate. (B) DGGE profiles of the enrichment culture. Subcultures that degraded 4-aminopyridine in 4 days (a, b, and c) and the subculture that did not degrade 4-aminopyridine (d) were analyzed by PCR-DGGE. The standard amplified fragments from strains 4AP-A, 4AP-B, 4AP-C, 4AP-D, 4AP-E, 4AP-F, and 4AP-G were loaded in lane M. The harvested cells of the enrichment culture were also used for PCR-DGGE (lane KM).