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Journal of Bacteriology, November 2001, p. 6551-6557, Vol. 183, No. 22
Unité Microbiologie et Environnement
and URA 2172,1 Laboratoire de
Génomique des Microorganismes
Pathogènes,2 and Laboratoire de
Référence des Mycobactéries,3
Institut Pasteur, 75724 Paris Cedex 15, and Département
de Microbiologie, Institut Français du Pétrole, 92852 Rueil-Malmaison Cedex,4 France
Received 9 July 2001/Accepted 29 August 2001
Rhodococcus ruber (formerly Gordonia
terrae) IFP 2001 is one of a few bacterial strains able to
degrade ethyl tert-butyl ether (ETBE), which is a major
pollutant from gasoline. This strain was found to undergo a spontaneous
14.3-kbp chromosomal deletion, which results in the loss of the ability
to degrade ETBE. Sequence analysis of the region corresponding to the
deletion revealed the presence of a gene cluster,
ethABCD, encoding a ferredoxin reductase, a cytochrome
P-450, a ferredoxin, and a 10-kDa protein of unknown function,
respectively. The EthB and EthD proteins could be easily detected by
sodium dodecyl sulfate-polyacrylamide gel electrophoresis and were
induced by ETBE in the wild-type strain. Upstream of
ethABCD lies ethR, which codes for a
putative positive transcriptional regulator of the AraC/XylS family.
Transformation of the ETBE-negative mutant by a plasmid carrying the
ethRABCD genes restored the ability to degrade ETBE.
Complementation was abolished if the plasmid carried
ethRABC only. The eth genes are located
in a DNA fragment flanked by two identical direct repeats of 5.6 kbp.
The ETBE-negative mutants carry a single copy of this 5.6-kbp repeat,
suggesting that the 14.3-kbp chromosomal deletion resulted from a
recombination between the two identical sequences. The 5.6-kbp repeat
is a class II transposon carrying a TnpA transposase, a truncated form
of the recombinase TnpR, and a terminal inverted repeat of 38 bp. The
truncated TnpR is encoded by an IS3-interrupted tnpR gene.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.22.6551-6557.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Cloning of a Genetically Unstable Cytochrome P-450
Gene Cluster Involved in Degradation of the Pollutant Ethyl
tert-Butyl Ether by Rhodococcus
ruber
*
Corresponding author. Mailing address: Unité
Microbiologie et Environnement, Département des Biotechnologies,
Institut Pasteur, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France.
Phone: 33 1 40 61 37 04. Fax: 33 1 45 68 87 90. E-mail:
chauvaux{at}pasteur.fr.
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