Journal of Bacteriology, July 2000, p. 3784-3793, Vol. 182, No. 13
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
andDepartment of Microbiology and Immunology and Pulp and Paper Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
Received 28 January 2000/Accepted 4 April 2000
We have cloned and sequenced the dit gene cluster
encoding enzymes of the catabolic pathway for abietane diterpenoid
degradation by Pseudomonas abietaniphila BKME-9. The
dit gene cluster is located on a 16.7-kb DNA fragment
containing 13 complete open reading frames (ORFs) and 1 partial ORF.
The genes ditA1A2A3 encode the
and
subunits and the
ferredoxin of the dioxygenase which hydroxylates 7-oxodehydroabietic
acid to 7-oxo-11,12-dihydroxy-8,13-abietadien acid. The dioxygenase
mutant strain BKME-941 (ditA1::Tn5)
did not grow on nonaromatic abietanes, and transformed palustric and abietic acids to 7-oxodehydroabietic acid in cell suspension assays. Thus, nonaromatic abietanes are aromatized prior to further
degradation. Catechol 2,3-dioxygenase activity of xylE
transcriptional fusion strains showed induction of ditA1
and ditA3 by abietic, dehydroabietic, and
7-oxodehydroabietic acids, which support the growth of strain BKME-9,
as well as by isopimaric and 12,14-dichlorodehydroabietic acids, which
are diterpenoids that do not support the growth of strain BKME-9. In
addition to the aromatic-ring-hydroxylating dioxygenase genes, the
dit cluster includes ditC, encoding an extradiol ring cleavage dioxygenase, and ditR, encoding an
IclR-type transcriptional regulator. Although ditR is not
strictly required for the growth of strain BKME-9 on abietanes, a
ditR::Kmr mutation in a
ditA3::xylE reporter strain
demonstrated that it encodes an inducer-dependent transcriptional
activator of ditA3. An ORF with sequence similarity to
genes encoding permeases (ditE) is linked with genes
involved in abietane degradation.
Present address: Department of Chemical Engineering, University of
California, Berkeley, Calif.
This article has been cited by other articles:
| Appl. Environ. Microbiol. | Infect. Immun. | Eukaryot. Cell |
|---|---|---|
| Mol. Cell. Biol. | J. Virol. | Microbiol. Mol. Biol. Rev. |
| ALL ASM JOURNALS |