The culture was centrifuged at 20,000 × g for 10 min, and the supernatant was dried using a rotary evaporator. The dried

residues were dissolved in n-butanol and then dried again. The accumulated products in the dried residue were incubated with N,O-bis(trimethylsilyl)trifluoroacetamide at 100°C for 1.5 h. The trimethylsilylated products were analyzed by GC-MS as described below. Measurement and identification of 4-aminopyridine and its metabolites Concentrations of pyridines, including 4-aminopyridine and 4-amino-3-hydroxypyridine (Figure 1, compound IV), were measured using a Hitachi L-6200 HPLC system (Tokyo, Japan) equipped with a Cosmosil 5C18 PAQ column (4.6 × 150 mm; Nacalai GS-1101 nmr Tesque, Kyoto). The eluent was 20 mM potassium phosphate buffer (pH 2.5) containing 5 mM pentanesulfonate; the flow rate was 1.0 ml/min. 4-Aminopyridine

and 4-amino-3-hydroxypyridine were detected at 254 nm and had retention times of 5.4 and 7.6 min, respectively. The metabolites from 4-aminopyridine (4-amino-3-hydroxypyridine and 3,4-dihydroxypyridine; Figure 1) were identified and quantified using a GCMS-QP2010 Ultra (Shimadzu, Kyoto, Japan). A fused silica capillary column (InertCap 1MS; 0.25 mm × 30 m; GL Science) was used. Helium gas was the carrier at a linear velocity of 35 cm/s. The column temperature was programed from 50°C (held for 1 min) to 280°C at a rate of 5°C/min and then held at 280°C for 20 min. The peaks derived from the trimethylsilylated https://www.selleckchem.com/products/ly333531.html derivatives of 4-aminopyridine, 4-amino-3-hydroxypyridine, and 3,4-dihydroxypyridine appeared at 18.2, 24.5, and 20.9 min, respectively. The organic acids in the culture supernatant were derivatized by pentafluorobenzyl bromide according to a previously reported Sodium butyrate method [19] and analyzed by GC-MS as described above. The peaks derived from the pentafluorobenzyl formate appeared at 8.5 min. PCR-DGGE analysis (1) DNA extraction and PCR Aliquots

(1.5, 1.0, and 0.5 ml) of the enrichment culture were sampled at the early-, mid-, and late-exponential growth phases, respectively, and centrifuged. DNA in the cell pellets was extracted using Qiagen DNeasy Blood & Tissue Kit according to the manufacturer’s instructions (Nihon eido, Tokyo, Japan). The 16S rRNA genes were amplified from 0.5 μl DNA by PCR (50 μl reactions) using a Taq polymerase kit (TaKaRa BIO INC., Shiga, Japan) and the forward primer PRBA338GCf, which contains a GC clamp, and the reverse primer AZD5363 PRUN518r, which targets the V3 region of the 16S rRNA gene (Table 1); the primers were prepared as reported previously [20]. The following PCR protocol was used: initial denaturation at 95°C for 2 min; 35 cycles of denaturation at 95°C for 60 s, annealing at 60°C for 30 s, extension at 72°C for 30 s; and final extension at 72°C for 5 min. The 16S rRNA genes of isolated strains were amplified by PCR of DNA isolated from colonies.   (2) DGGE Approximately 100 to 200 ng of each PCR product was analyzed by electrophoresis on 1.