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Journal of Bacteriology, June 2001, p. 3663-3679, Vol. 183, No. 12
Biotechnology Research Center, The University
of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
Received 5 September 2000/Accepted 27 March 2001
The nucleotide sequences of the 27,939-bp-long upstream and
9,448-bp-long downstream regions of the
carAaAaBaBbCAc(ORF7)Ad genes of
carbazole-degrading Pseudomonas sp. strain CA10 were determined. Thirty-two open reading frames (ORFs) were identified, and
the car gene cluster was consequently revealed to
consist of 10 genes (carAaAaBaBbCAcAdDFE) encoding the
enzymes for the three-step conversion of carbazole to anthranilate and
the degradation of 2-hydroxypenta-2,4-dienoate. The high identities (68 to 83%) with the enzymes involved in 3-(3-hydroxyphenyl)propionic acid degradation were observed only for CarFE. This observation, together with the fact that two ORFs are inserted between carD
and carFE, makes it quite likely that the
carFE genes were recruited from another locus. In the
21-kb region upstream from carAa,
aromatic-ring-hydroxylating dioxygenase genes (ORF26, ORF27, and ORF28)
were found. Inductive expression in carbazole-grown cells and the
results of homology searching indicate that these genes encode the
anthranilate 1,2-dioxygenase involved in carbazole degradation.
Therefore, these ORFs were designated antABC. Four
homologous insertion sequences, IS5car1 to
IS5car4, were identified in the neighboring regions of
car and ant genes. IS5car2
and IS5car3 constituted the putative composite transposon containing antABC. One-ended transposition of
IS5car2 together with the 5' portion of
antA into the region immediately upstream of
carAa had resulted in the formation of
IS5car1 and ORF9. In addition to the insertion
sequence-dependent recombination, gene duplications and presumed gene
fusion were observed. In conclusion, through the above gene
rearrangement, the novel genetic structure of the car
gene cluster has been constructed. In addition, it was also revealed
that the car and ant gene clusters are
located on the megaplasmid pCAR1.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.12.3663-3679.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Genetic Characterization and Evolutionary
Implications of a car Gene Cluster in the Carbazole
Degrader Pseudomonas sp. Strain CA10
*
Corresponding author. Mailing address: Biotechnology
Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. Phone: 81(3)5841-3067. Fax: 81(3)5841-8030. E-mail: aseigyo{at}mail.ecc.u-tokyo.ac.jp.
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