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Appl. Environ. Microbiol., 02 1996, 601-606, Vol 62, No. 2
WA Duetz, S Marques, B Wind, JL Ramos and JG van Andel
In earlier studies, the pathway of toluene and m- and p-xylene degradation
(TOL pathway) in Pseudomonas putida (pWW0) was found to be subject to
catabolite repression when the strain was grown at the maximal rate on
glucose or succinate in the presence of an inducer. This report describes
catabolite repression of the TOL pathway by succinate in chemostat cultures
run at a low dilution rate (D = 0.05 h- 1) under different conditions of
inorganic-nutrient limitation. The activity of benzylalcohol dehydrogenase
(BADH) in cell extracts was used as a measure of the expression of the TOL
upper pathway. When cells were grown in the presence of 10 to 15 mM
succinate under conditions of phosphate or sulfate limitation, the BADH
activity in response to the nonmetabolizable inducer o-xylene was less than
2% of that of cells grown under conditions of succinate limitation. Less
repression was found under conditions of ammonium or oxygen limitation (2
to 10% and 20 to 35%, respectively, of the BADH levels under succinate
limitation). The BADH expression levels determined under the different
growth conditions appeared to correlate well with the mRNA transcript
levels from the upper pathway promoter (Pu), which indicates that
repression was due to a blockage at the transcriptional level. The
meta-cleavage pathway was found to be less susceptible to catabolite
repression. The results obtained suggest that the occurrence of catabolite
repression is related to a high-energy status of the cells rather than to a
high growth rate or directly to the presence of growth- saturating
concentrations of a primary carbon and energy source.
Copyright © 1996, American Society for Microbiology
Catabolite repression of the toluene degradation pathway in Pseudomonas putida harboring pWW0 under various conditions of nutrient limitation in chemostat culture
Laboratory for Waste Materials and Emissions, National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.
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