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Appl. Environ. Microbiol., Jun 1995, 2308-2313, Vol 61, No. 6
SF Nishino and JC Spain
Previous studies have shown that the biodegradation of nitrobenzene by
Pseudomonas pseudoalcaligenes JS45 proceeds by the reduction of
nitrobenzene through nitrosobenzene and hydroxylaminobenzene, followed by
rearrangement to 2-aminophenol, which then undergoes meta ring cleavage. We
report here the isolation of a Comamonas sp. that uses an oxidative pathway
for the complete mineralization of nitrobenzene. The isolate, designated
strain JS765, uses nitrobenzene as a sole source of carbon, nitrogen, and
energy. Nitrobenzene-grown cells oxidized nitrobenzene, with the
stoichiometric release of nitrite. Extracts of nitrobenzene-grown JS765
showed high levels of catechol 2,3-dioxygenase activity that were not
abolished by heating the cell extracts to 60(deg)C for 10 min. The ring
cleavage product had an absorbance maximum at 375 nm, consistent with that
of 2-hydroxymuconic semialdehyde. Both NAD-dependent dehydrogenase and
NAD-independent hydrolase activities towards 2-hydroxymuconic semialdehyde
were induced in extracts of nitrobenzene-grown cells. Catechol accumulated
in the reaction mixture when cells preincubated with 3-chlorocatechol were
incubated with nitrobenzene. Conversion of nitrobenzene to catechol by
induced cells in the presence of 3-chlorocatechol and (sup18)O(inf2)
demonstrated the simultaneous incorporation of two atoms of oxygen, which
indicated that the initial reaction was dioxygenation. The results indicate
that the catabolic pathway involves an initial dioxygenase attack on
nitrobenzene with the release of nitrite and formation of catechol, which
is subsequently degraded by a meta cleavage pathway.
Copyright © 1995, American Society for Microbiology
Oxidative Pathway for the Biodegradation of Nitrobenzene by Comamonas sp. Strain JS765
AL/EQC, Tyndall Air Force Base, Florida 32403-5323
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