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Applied and Environmental Microbiology, July 2001, p. 3102-3109, Vol. 67, No. 7
Institut für Mikrobiologie,
Westfälische Wilhelms-Universität Münster, D-48149
Münster, Germany,1 and
Monsanto Company, St. Louis, Missouri 631672
Received 18 January 2001/Accepted 23 April 2001
Since Pseudomonas aeruginosa is capable of biosynthesis
of polyhydroxyalkanoic acid (PHA) and rhamnolipids, which contain lipid
moieties that are derived from fatty acid biosynthesis, we investigated
various fab mutants from P. aeruginosa with
respect to biosynthesis of PHAs and rhamnolipids. All isogenic
fabA, fabB, fabI, rhlG, and phaG mutants from
P. aeruginosa showed decreased PHA accumulation and
rhamnolipid production. In the phaG (encoding transacylase) mutant rhamnolipid production was only slightly decreased. Expression of phaG from Pseudomonas
putida and expression of the
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.7.3102-3109.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Role of Fatty Acid De Novo Biosynthesis in Polyhydroxyalkanoic
Acid (PHA) and Rhamnolipid Synthesis by Pseudomonads: Establishment of
the Transacylase (PhaG)-Mediated Pathway for PHA Biosynthesis in
Escherichia coli
-ketoacyl reductase gene
rhlG from P. aeruginosa
in these mutants indicated that PhaG catalyzes diversion of
intermediates of fatty acid de novo biosynthesis towards PHA
biosynthesis, whereas RhlG catalyzes diversion towards rhamnolipid
biosynthesis. These data suggested that both
biosynthesis pathways are competitive. In order to investigate whether
PhaG is the only linking enzyme between fatty acid de novo
biosynthesis and PHA biosynthesis, we generated five Tn5
mutants of P. putida strongly impaired in PHA
production from gluconate. All mutants were complemented by the
phaG gene from P. putida, indicating that the
transacylase-mediated PHA biosynthesis route represents the
only metabolic link between fatty acid de novo biosynthesis and PHA
biosynthesis in this bacterium. The transacylase-mediated
PHA biosynthesis route from gluconate was established in recombinant
E. coli, coexpressing the class II PHA synthase gene
phaC1 together with the phaG gene from P. putida, only when fatty acid de novo biosynthesis was partially inhibited by triclosan. The accumulated PHA contributed to 2 to 3% of
cellular dry weight.
*
Corresponding author. Mailing address: Institut
für Mikrobiologie, Westfälische Wilhelms-Universität
Münster, Corrensstrasse 3, D-48149 Münster, Germany. Phone:
49 251 8339848. Fax: 49 251 833 8388. E-mail.
rehm{at}unimuenster.de.
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