Aerobic degradation of dinitrotoluenes and pathway for bacterial degradation of 2,6-dinitrotoluene

An oxidative pathway for the mineralization of 2,4-dinitrotoluene (2,4-DNT) by Burkholderia sp, strain DNT has been reported previously. We report her e the isolation of additional strains with the ability to mineralize 2,4-DN T by the same pathway and the isolation and characterization of bacterial s trains that mineralize 2,6-dinitrotoluene (2,6-DNT) by a different pathway. Burkholderia cepacia strain JS850 and Hydrogenophaga palleronii strain JS8 63 grew on 2,6-DNT as the sole source of carbon and nitrogen. The initial s teps in the pathway for degradation of 2,6-DNT were determined by simultane ous induction, enzyme assays, and identification of metabolites through mas s spectroscopy and nuclear magnetic resonance, 2,6-DNT was converted to 3-m ethyl-4-nitrocatechol by a dioxygenation reaction accompanied by the releas e of nitrite, 3-Methyl-4-nitrocatechol was the substrate for extradiol ring cleavage yielding 2-hydroxy-5-nitro-6-oxohepta-2,4-dienoic acid, which was converted to 2-hydroxy-5-nitropenta-2,4-dienoic acid. 2,4-DNT-degrading st rains also converted 2,6-DNT to 3-methyl-4-nitrocatechol but did not metabo lize the 3-methyl-4-nitrocatechol. Although 2,6-DNT prevented the degradati on of 2,4-DNT by 2,4-DNT-degrading strains, the effect was not the result o f inhibition of 2,4-DNT dioxygenase by 2,6-DNT or of 4-methyl-5-nitrocatech ol monooxygenase by 3-methyl-4-nitrocatechol.