Affiliation:
1. Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain
Abstract
ABSTRACT
Pseudomonas aeruginosa
JB2 can use 2-chlorobenzoate (2-CBa), 3-CBa, 2,3-dichlorobenzoate (2,3-DCBa), and 2,5-DCBa as sole carbon and energy sources, whereas strain 142 can only grow on 2-CBa and 2,4-DCBa. Both strains, however, harbor the same halobenzoate 1,2-dioxygenase (
ohbAB
) and chlorocatechol (
clcABD
) degradation genes necessary for the metabolism of
ortho
-CBas. In addition, the
hybABCD
operon, encoding a salicylate 5-hydroxylase, is also found in both strains. The expression of
ohbAB
,
hybABCD
, and
clcABD
operons was measured in cultures grown on different CBas as the sole carbon source and also in glucose-grown cells supplemented with CBas as inducers. A method to standardize real-time reverse transcription-PCR experimental data was used that allows the comparison of semiquantitative mRNA accumulation in different strains and culture conditions. In both strains, the
ohb
and
hyb
systems were induced in cells grown on 2-CBa or DCBas, whereas
clc
was induced only by DCBas. Repression by catabolite was observed both on
ohb
and
clc
systems in glucose-grown cells. Chlorocatechol 1,2-dioxygenase activity in JB2 was detected even in
clc
-repressed conditions, confirming the presence of additional isofunctional genes previously detected in
P. aeruginosa
142. Although similar levels of induction of
ohbAB
were observed in strain JB2 grown on either benzoate, monochlorobenzoates, or DCBas, the
ohbAB
operon of strain 142 was only strongly induced by growth on 2-CBa and, to a lesser extent, on 2,4-DCBa. This observation suggests that regulation of the
ohbAB
operon may be different in both strains. The concomitant induction of
ohb
and
hyb
by CBas may allow the formation of hybrid halobenzoate dioxygenase(s) composed of Ohb/Hyb dioxygenase subunits and Hyb ferredoxin/ferredoxin reductase components.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
31 articles.
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