Degradation of 2,4-dinitrophenol and selected nitroaromatic compounds by Sphingomonas sp UG30

Sphingomonas strain UG30 mineralizes both p-nitrophenol (PNP) and pentachlo rophenol (PCP). Our current studies showed that UG30 oxidatively metabolize d certain other p-substituted nitrophenols, i.e., p-nitrocatechol, 2,4-dini trophenol (2,4-DNP), and 4,6-dinitrocresol with liberation of nitrite. 2,6- DNP, o- or m-nitrophenol picric acid, or the herbicide dinoseb were not met abolized Studies using C-14-labelled 2,il-DNP indicated that in glucose-glu tamate broth cultures of UG30, greater than 90% of 103 mu M 2,4-DNP was tra nsformed to other compounds, while 8-19% of the 2,4-DNP was mineralized wit hin 5 days. A significant portion (20-50%) of the 2,4-DNP was metabolized t o highly polar metabolite(s) with one major unidentified metabolite accumul ating from 5 to 25% of the initial radioactivity. The amounts of 2,4-DNP mi neralized and converted to polar metabolites was affected by glutamate conc entration in the medium. Nitrophenolic compounds metabolized by UG30 were a lso suitable substrates for the UG30 PCP-4-monooxygenase (pcpB gene express ed in Escherichia coli) which is likely central to degradation of these com pounds. The wide substrate range of UG30 could render this strain useful in bioremediation of some chemically contaminated soils.