Sf. Nishino et Jc. Spain, DEGRADATION OF NITROBENZENE BY A PSEUDOMONAS-PSEUDOALCALIGENES, Applied and environmental microbiology, 59(8), 1993, pp. 2520-2525
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.