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Journal of Bacteriology, October 2000, p. 5849-5863, Vol. 182, No. 20
Institut Biologie II,
Mikrobiologie,1 and Organische Chemie
und Biochemie,2 Universität Freiburg,
D-79104 Freiburg, Germany
Received 28 March 2000/Accepted 31 July 2000
Genes involved in the anaerobic metabolism of phenol in the
denitrifying bacterium Thauera aromatica have been studied.
The first two committed steps in this metabolism appear to be
phosphorylation of phenol to phenylphosphate by an unknown phosphoryl
donor ("phenylphosphate synthase") and subsequent carboxylation of
phenylphosphate to 4-hydroxybenzoate under release of phosphate
("phenylphosphate carboxylase"). Both enzyme activities are
strictly phenol induced. Two-dimensional gel electrophoresis allowed
identification of several phenol-induced proteins. Based on N-terminal
and internal amino acid sequences of such proteins, degenerate
oligonucleotides were designed to identify the corresponding genes. A
chromosomal DNA segment of about 14 kbp was sequenced which contained
10 genes transcribed in the same direction. These are organized in
two adjacent gene clusters and include the genes coding for five
identified phenol-induced proteins. Comparison with sequences in the
databases revealed the following similarities: the gene products of two open reading frames (ORFs) are each similar to either the central part
and N-terminal part of phosphoenolpyruvate synthases. We propose that
these ORFs are components of the phenylphosphate synthase system. Three
ORFs showed similarity to the ubiD gene product,
3-octaprenyl-4-hydroxybenzoate carboxy lyase; UbiD catalyzes the
decarboxylation of a 4-hydroxybenzoate analogue in ubiquinone biosynthesis. Another ORF was similar to the ubiX gene
product, an isoenzyme of UbiD. We propose that (some of) these four
proteins are involved in the carboxylation of phenylphosphate.
A 700-bp PCR product derived from one of these ORFs cross-hybridized
with DNA from different Thauera and Azoarcus
strains, even from those which have not been reported to grow with
phenol. One ORF showed similarity to the mutT gene product,
and three ORFs showed no strong similarities to sequences in the
databases. Upstream of the first gene cluster, an ORF which is
transcribed in the opposite direction codes for a protein highly
similar to the DmpR regulatory protein of Pseudomonas
putida. DmpR controls transcription of the genes of aerobic
phenol metabolism, suggesting a similar regulation of anaerobic phenol
metabolism by the putative regulator.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Genes Involved in Anaerobic Metabolism of Phenol
in the Bacterium Thauera aromatica
*
Corresponding author. Mailing address: Institut
Biologie II, Mikrobiologie, Schänzlestr. 1, D-79104
Freiburg, Germany. Phone: 49-761-2032649. Fax:
49-761-2032626. E-mail: fuchsgeo{at}uni-freiburg.de.
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