f Dihydroaeruginoic acid synthetase and pyochelin synthetase, products of the pchEF, are induced by extracellular pyochelin in Pseudornonas aeruginosa
- Authors: Cornelia Reimmann, Laura Serino†, Markus Beyeler‡, Dieter Haa2
- 2Author for correspondence: Dieter Haas. Tel: +41 21 692 56 31. Fax: +41 21 692 56 35.e-mail: Dieter.Haas@lbm.uniI.ch
- Microbiology, November 1998 144: 3135-3148, doi: 10.1099/00221287-144-11-3135
- Subject: Physiology And Growth
- Published Online:
SUMMARY: The siderophore pyochelin of Pseudomonas aeruginosa is derived from one molecule of salicylate and two molecules of cysteine. Two cotranscribed genes, pChEF8 encoding peptide synthetases have been identified and characterized. pchE was required for the conversion of salicylate to dihydroaeruginoate (Dha), the condensation product of salicylate and one cysteine residue and pchF was essential for the synthesis of pyochelin from Dha. The deduced PchE(156 kDa) and PchF (197 kDa) proteins had adenylation, thiolation and condensationkyclization motifs arranged as modules which are typical of those peptide synthetases forming thiazoline rings. The pchEF genes were coregulated with the pchDCBA operon, which provides enzymes for the synthesis (PchBA) and activation (PchD) of salicylate as well as a putative thioesterase (PchC). Expression of a translational pchf-'/acZ fusion was strictly dependent on the PchR regulator and was induced by extracellular pyochelin, the end product of the pathway. Iron replete conditions led t o Fur (ferric uptake regulator)-dependent repression of the pchE ‘-’laciZ fusion. A translational pchD‘-’lacZ fusion was also positively regulated by PchR and pyochelin and repressed by Fur and iron. Thus, autoinduction by pyochelin (or ferric pyochelin) and repression by iron ensure a sensitive control of the pyochelin pathway in P. aeruginosa.
Present address: Emmenegger AG, CH-4416 Bubendorf, Switzerland.
Present address: University of Bristol, Department of Pathology and Microbiology, Bristol BS8 ITD, UK.
- Keyword(s): Pseudomonas aeruginosa, siderophore, non-ri bosomal peptide synthesis, autoinduction, pyochelin
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