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Appl Environ Microbiol, January 1998, p. 246-252, Vol. 64, No. 1
Fraunhofer-Institut für
Grenzflächen- und Bioverfahrenstechnik,1
and
Institut für Mikrobiologie2
and
Institut für Organische
Chemie3 der Universität Stuttgart, D-70569
Stuttgart, Germany, and
Armstrong Laboratory AL/EQC, Tyndall
Air Force Base, Florida 32403-52334
Received 22 August 1997/Accepted 3 November 1997
Because of its high electron deficiency, initial microbial
transformations of 2,4,6-trinitrotoluene (TNT) are characterized by
reductive rather than oxidation reactions. The reduction of the nitro
groups seems to be the dominating mechanism, whereas hydrogenation of
the aromatic ring, as described for picric acid, appears to be of minor
importance. Thus, two bacterial strains enriched with TNT as a sole
source of nitrogen under aerobic conditions, a gram-negative strain
called TNT-8 and a gram-positive strain called TNT-32, carried out
nitro-group reduction. In contrast, both a picric acid-utilizing
Rhodococcus erythropolis strain, HL PM-1, and a
4-nitrotoluene-utilizing Mycobacterium sp. strain, HL
4-NT-1, possessed reductive enzyme systems, which catalyze ring
hydrogenation, i.e., the addition of a hydride ion to the aromatic ring
of TNT. The hydride-Meisenheimer complex thus formed (H
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Initial Reductive Reactions in Aerobic Microbial
Metabolism of 2,4,6-Trinitrotoluene
-TNT) was further converted to a yellow metabolite,
which by electrospray mass and nuclear magnetic resonance spectral
analyses was established as the protonated dihydride-Meisenheimer
complex of TNT (2H
-TNT). Formation of hydride complexes
could not be identified with the TNT-enriched strains TNT-8 and TNT-32,
or with Pseudomonas sp. clone A (2NT
), for
which such a mechanism has been proposed. Correspondingly, reductive
denitration of TNT did not occur.
*
Corresponding author. Mailing address:
Fraunhofer-Institut für Grenzflächen- und
Bioverfahrenstechnik, Nobelstr. 12, D-70569 Stuttgart, Germany. Phone:
49 (0) 711/685-5487. Fax: 49 (0) 711/685-5725. E-mail:
hjkimb{at}uni-stuttgart.de.
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