DEGRADATION OF NITROBENZENE BY A PSEUDOMONAS-PSEUDOALCALIGENES

A Pseudomonas pseudoalcaligenes able to use nitrobenzene as the sole s ource of carbon, nitrogen, and energy was isolated from soil and groun dwater contaminated with nitrobenzene. The range of aromatic substrate s able to support growth was limited to nitrobenzene, hydroxylaminoben zene, and 2-aminophenol. Washed suspensions of nitrobenzene-grown cell s removed nitrobenzene from culture fluids with the concomitant releas e of ammonia. Nitrobenzene, nitrosobenzene, hydroxylaminobenzene, and 2-aminophenol stimulated oxygen uptake in resting cells and in extract s of nitrobenzene-grown cells. Under aerobic and anaerobic conditions, crude extracts converted nitrobenzene to 2-aminophenol with oxidation of 2 mol of NADPH. Ring cleavage, which required ferrous iron, produc ed a transient yellow product with a maximum A380. In the presence of NAD, the product disappeared and NADH was produced. In the absence of NAD, the ring fission product was spontaneously converted to picolinic acid, which was not further metabolized. These results indicate that the catabolic pathway involves the reduction of nitrobenzene to nitros obenzene and then to hydroxylaminobenzene; each of these steps require s 1 mol of NADPH. An enzyme-mediated Bamberger-like rearrangement conv erts hydroxylaminobenzene to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. The mechanism for releas e of ammonia and subsequent metabolism are under investigation.