Initial reactions of anaerobic metabolism of alkylbenzenes in denitrifying and sulfate-reducing bacteria |
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Authors: | R Rabus J Heider |
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Institution: | Max-Planck-Institut für marine Mikrobiologie, Celsiusstrasse 1, D-28359 Bremen, Germany, DE Universit?t Freiburg, Institut für Biologie II, Mikrobiologie, Sch?nzlestrasse 1, D-79104 Freiburg, Germany e-mail: heiderj@ruf.uni-freiburg.de Tel. +49-761-203-2774; Fax +49-761-203-2626, DE
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Abstract: | The initial activation reactions of anaerobic oxidation of the aromatic hydrocarbons toluene and ethylbenzene were investigated
in cell extracts of a toluene-degrading, sulfate-reducing bacterium, Desulfobacula toluolica, and in cell extracts of strain EbN1, a denitrifying bacterium capable of degrading toluene and ethylbenzene. Extracts of
toluene-grown cells of both species catalysed the addition of fumarate to the methyl group of phenyl-14C]-toluene and formed 14C]-labeled benzylsuccinate. Extracts of ethylbenzene-grown cells of strain EbN1 did not catalyse this reaction, but catalysed
the formation of 1-phenylethanol and acetophenone from methylene-14C]-ethylbenzene. Toluene-grown cells of D. toluolica and strain EbN1 synthesised highly induced polypeptides corresponding to the large subunits of benzylsuccinate synthase from
Thauera aromatica. These polypeptides were absent in strain EbN1 after growth on ethylbenzene, although a number of different polypeptides
were highly induced. Thus, formation of benzylsuccinate from toluene and fumarate appears to be the general initiating step
in anaerobic toluene degradation by bacteria affiliated with the phylogenetically distinct β-subclass (strain EbN1 and T. aromatica) and δ-subclass (D. toluolica) of the Proteobacteria. Anaerobic ethylbenzene oxidation proceeds via a different pathway involving a two-step oxidation
of the methylene group to an alcohol and an oxo group; these steps are most probably followed by a biotin-independent carboxylation
reaction and thiolytic cleavage.
Received: 16 March 1998 / Accepted: 27 June 1998 |
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Keywords: | Anaerobic alkylbenzene metabolism Sulfate-reducing bacteria Denitrifying bacteria Desulfobacula toluolica Toluene Benzylsuccinate Ethylbenzene 1-Phenylethanol Acetophenone Benzoyl-CoA |
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