Degradation of p-nitrophenol by Achromobacter xylosoxidans Ns isolated from wetland sediment

Achromobacter xylosoxidans Ns strain, capable of utilizing p-nitrophenol (PNP) as the sole source of carbon, energy, and nitrogen, was isolated from wetland sediment and confirmed based on 16S rRNA gene sequence. The strain Ns could tolerate concentrations of PNP up to 1.8 mM, and degradation of PNP was achieved in 7 d at 30 °C in the dark under aerobic conditions. Biodegradation of PNP occurred quickly at an optimal pH of 7.0 and higher, and at 0.5% salt (NaCl) contents. During bacterial growth on PNP, 4-nitrocatechol was observed as a key degradation intermediate using a combination of techniques, including HPLC, UV–visible spectra, and comparison with the authentic standard. In a similar way, a second degradation intermediate was identified to be 1,2,4-benzenetriol. Moreover, A. xylosoxidans Ns could also degrade 3-nitrophenol as the sole source of carbon, nitrogen, and energy, but 2-nitrophenol could not. The experimental results showed that bacteria indigenous to the wetland sediment are capable of degradading PNP and chemicals with similar structures.