Involvement of a transformylase enzyme in siderophore synthesis in Pseudomonas aeruginosa The GenBank accession number for the sequence reported in this paper is U07359.

Abstract

Fluorescent pseudomonads produce yellow-green siderophores when grown under conditions of iron starvation. Here, the characterization of the pvdF gene, which is required for synthesis of the siderophore pyoverdine by Pseudomonas aeruginosa strain PAO1, is described. A P. aeruginosa pvdF mutant was constructed and found to be defective for production of pyoverdine, demonstrating the involvement of PvdF in pyoverdine synthesis. Transcription analysis showed that expression of pvdF was regulated by the amount of iron in the growth medium, consistent with its role in siderophore production. DNA sequencing showed that pvdF gives rise to a protein of 31 kDa that has similarity with glycinamide ribonucleotide transformylase (GART) enzymes involved in purine synthesis from a wide range of eukaryotic and prokaryotic species. Chemical analyses of extracts from wild-type and pvdF mutant bacteria indicated that the PvdF enzyme catalyses the formylation of N 5 -hydroxyornithine to give rise to N 5 -formyl-N 5 -hydroxyornithine, a component of pyoverdine. These studies enhance understanding of the enzymology of pyoverdine synthesis, and to the best of the authors ' knowledge provide the first example of involvement of a GART-type enzyme in synthesis of a secondary metabolite.

Expression of the quorum-sensing regulatory protein LasR is strongly affected by iron and oxygen concentrations in cultures of Pseudomonas aeruginosa irrespective of cell density

“…Siderophores (pyoverdine and pyochelin) were measured with a microtitre plate fluorometer (MFX Microtitre Plate Fluorometer, DYNEX). Fluorescence was determined by exciting the supernatant of the culture at 400 nm for pyoverdine and 355 nm for pyochelin; the emission was measured at 460 nm for pyoverdine and 440 nm for pyochelin (McMorran et al, 2001;Ankenbauer et al, 1985). Biomass dry weight was determined gravimetrically as described previously (Sabra et al, 2000).…”

Siderophore-mediated signaling regulates virulence factor production in Pseudomonas aeruginosa

“…We first addressed the question, does pyoverdine regulate the expression of genes encoding pyoverdine-synthesis enzymes? This question was examined with a P. aeruginosa pvdF mutant strain that makes no detectable pyoverdine (42) in conjunction with the promoter reporter construct pMP190::PpvdE in which expression of lacZ depends on transcription initiated from the upstream pvdE promoter (18,39). pvdE promoter activity was much lower in the pvdF mutant than in wild-type bacteria (Fig.…”

Iron-binding ligands and their role in the ocean biogeochemistry of iron

“…Are they of direct biological origin? The discovery that siderophore-like compounds are produced by various marine microbes in laboratory culture, [66][67][68][69][70] and the similar conditional formation constants of seawater Fe-binding ligands and known siderophores suggested that the seawater ligands do have a direct biological origin and are probably not very large in molecular size (300-1000 Da). [71,72] This provokes the intriguing paradigm of microbes competing for this scarce trace element by sequestering a specific iron-collection 'agent'.…”