Studies on Nitrobenzene Metabolism by a Comamonas sp. Strain JS7651

Funded studies focused on the biodegradation of nitrobenzene by Comamonas sp. strain JS765, which was isolated in Dr. Jim C. Spain's laboratory, Tyndall AFB. The genes encoding the nitrobenzene dioxygenase system were cloned and sequenced from JS765. The nitrobenzene dioxygenase enzyme system shares high amino acid homology with other identified nitroarene dioxygenase enzymes, in particular the 2-nitrotoluene dioxygenase system from Pseudomonas sp. strain JS42. Nitrobenzene dioxygenase was purified to near homogeneity and had characteristics typical of dioxygenase enzymes. The substrate specificity of nitrobenzene dioxygenase was examined by conducting biotransformations. Based on the substrates examined, it appeared that the substrate specificity of nitrobenzene dioxygenase is different from related enzymes. Gene reporter technology was used to examine the transcriptional regulation of nitrobenzene and 2-nitrotoluene dioxygenase from JS765 and JS42, respectively. Results indicate that both dioxygenases are induced in the presence of salicylate and the respective nitroaromatic compound.