Functional analysis of pyochelin-/enantiopyochelin-related genes from a pathogenicity island of Pseudomonas aeruginosa strain PA14
Genomic islands are foreign DNA blocks inserted in so-called regions of genomic plasticity (RGP). Depending on their gene content, they are classified as pathogenicity, symbiosis, metabolic, fitness or resistance islands, although a detailed functional analysis is often lacking. Here we focused on a...
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Veröffentlicht in: | Biometals 2014-06, Vol.27 (3), p.559-573 |
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Zusammenfassung: | Genomic islands are foreign DNA blocks inserted in so-called regions of genomic plasticity (RGP). Depending on their gene content, they are classified as pathogenicity, symbiosis, metabolic, fitness or resistance islands, although a detailed functional analysis is often lacking. Here we focused on a 34-kb pathogenicity island of
Pseudomonas aeruginosa
PA14 (PA14GI-6), which is inserted at RGP5 and carries genes related to those for pyochelin/enantiopyochelin biosynthesis. These enantiomeric siderophores of
P. aeruginosa
and certain strains of
Pseudomonas protegens
are assembled by a thiotemplate mechanism from salicylate and two molecules of cysteine. The biochemical function of several proteins encoded by PA14GI-6 was investigated by a series of complementation analyses using mutants affected in potential homologs. We found that
PA14_54940
codes for a bifunctional salicylate synthase/salicyl-AMP ligase (for generation and activation of salicylate), that
PA14_54930
specifies a dihydroaeruginoic acid (Dha) synthetase (for coupling salicylate with a cysteine-derived thiazoline ring), that
PA14_54910
produces a type II thioesterase (for quality control), and that
PA14_54880
encodes a serine
O
-acetyltransferase (for increased cysteine availability). The structure of the PA14GI-6-specified metabolite was determined by mass spectrometry, thin-layer chromatography, and HPLC as (
R
)-Dha, an iron chelator with antibacterial, antifungal and antitumor activity. The conservation of this genomic island in many clinical and environmental
P. aeruginosa
isolates of different geographical origin suggests that the ability for Dha production may confer a selective advantage to its host. |
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ISSN: | 0966-0844 1572-8773 |
DOI: | 10.1007/s10534-014-9729-4 |