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Applied and Environmental Microbiology, January 2001, p. 162-171, Vol. 67, No. 1
Department of Cell and Molecular Biology,
Umeå University, S-901 87 Umeå,1 and
Department of Microbiology, National Defence Research
Establishment, S-901 82 Umeå,3 Sweden,
Department of Biosciences, Division of General
Microbiology, Viikki Biocenter, University of Helsinki, FIN-00014
Helsinki, Finland2
Received 13 July 2000/Accepted 17 October 2000
Pathway substrates and some structural analogues directly activate
the regulatory protein DmpR to promote transcription of the
dmp operon genes encoding the (methyl)phenol degradative
pathway of Pseudomonas sp. strain CF600. While a wide range
of phenols can activate DmpR, the location and nature of substituents
on the basic phenolic ring can limit the level of activation and thus
utilization of some compounds as assessed by growth on plates. Here we
address the role of the aromatic effector response of DmpR in
determining degradative properties in two soil matrices that
provide different nutritional conditions. Using the wild-type system
and an isogenic counterpart containing a DmpR mutant with enhanced
ability to respond to para-substituted phenols, we
demonstrate (i) that the enhanced in vitro biodegradative capacity of
the regulator mutant strain is manifested in the two different soil types and (ii) that exposure of the wild-type strain to
4-methylphenol-contaminated soil led to rapid selection of a
subpopulation exhibiting enhanced capacities to degrade the
compound. Genetic and functional analyses of 10 of these derivatives
demonstrated that all harbored a single mutation in the
sensory domain of DmpR that mediated the phenotype in each case. These
findings establish a dominating role for the aromatic effector response
of DmpR in determining degradation properties. Moreover, the results
indicate that the ability to rapidly adapt regulator properties to
different profiles of polluting compounds may underlie
the evolutionary success of DmpR-like regulators in controlling
aromatic catabolic pathways.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.1.162-171.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Role of the DmpR-Mediated Regulatory Circuit in Bacterial
Biodegradation Properties in Methylphenol-Amended Soils
*
Corresponding author. Mailing address: Department of
Cell and Molecular Biology, Umeå University, S-901 87 Umeå, Sweden.
Phone: 46 90 7852534. Fax: 46 90 771420. E-mail:
victoria.shingler{at}cmb.umu.se.
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