The X-ray structure of the pyochelin Fe3+ complex.

By X-ray structure analysis it could be shown that from the solution equilibrium of pyochelin I and II, differing in the stereochemistry at C-2" (1a and 1b), crystals of the Fe3+ complex of the steroisomer 1a are formed with a 1:1 metal-to-ligand ratio. Ligand sites are the carboxylate and the phenolate anions and the two nitrogen atoms. Two equivalent ferri-pyochelin moieties are held together by a hydroxy and an acetate unit which satisfy the remaining two coordination sites of Fe3+.

The stereoisomers of pyochelin, a siderophore of Pseudomonas aeruginosa.

The Pseudomonas aeruginosa siderophore pyochelin is obtained from the bacterial culture medium as a mixture of two epimers. Chromatically isolated pure stereoisomers equilibrate readily in most solvents. Experiments will be reported which allow to isolate one of the isomers in pure form and which shed some additional light on the epimerization reaction.

Diastereomeric pyoverdin-chromium(III) complexes.

Coordination isomeric diastereomeric Cr3+ complexes of the pyoverdin of Pseudomonas aeruginosa ATCC 15692 could be separated by chromatography and characterized by spectroscopic methods.

The structures of the pyoverdins from two Pseudomonas fluorescens strains accepted mutually by their respective producers.

From Pseudomonas fluorescens PL7 and PL8 structurally related pyoverdins were isolated and their primary structures were elucidated by spectroscopic methods and degradation reactions. Despite of some structural differences both Fe(III) complexes are taken up by either strain with a high rate. The implications regarding the recognition at the cell surface are discussed.

Siderophore-mediated iron uptake in fluorescent Pseudomonas: characterization of the pyoverdine-receptor binding site of three cross-reacting pyoverdines.

Two Pseudomonas fluorescens and one Pseudomonas aeruginosa strains, although producing structurally different pyoverdines, demonstrated highly efficient cross-reactions when tested for pyoverdine-mediated iron uptake. A ferripyoverdine receptor-deficient mutant of the P. aeruginosa strain was unable to use any of the three pyoverdines. Moreover, the three strains presented each a specific outer membrane siderophore-receptor pattern. Thus, the capacity of using heterologous pyoverdines was related not to the presence of supplementary specific ferripyoverdine receptors but to the existence within the respective pyoverdine-peptide chains of a common dipeptide motif which should act as the receptor-binding site for the three pyoverdines. Other pyoverdines sharing the same motif but at another position within the peptide chain were not efficient in iron transport, demonstrating the importance of the spatial position of the binding site.

Siderotyping of fluorescent pseudomonads: characterization of pyoverdines of Pseudomonas fluorescens and Pseudomonas putida strains from Antarctica.

Five independent fluorescent pseudomonad isolates originating from Antarctica were analysed for their pyoverdine systems. A pyoverdine-related siderotyping, which involved pyoverdine-induced growth stimulation, pyoverdine-mediated iron uptake, pyoverdine analysis by electrophoresis and isoelectric focusing, revealed three different pyoverdine-related siderotypes among the five isolates. One siderotype, including Pseudomonas fluorescens 1W and P. fluorescens 10CW, was identical to that of P. fluorescens ATCC 13525. Two other strains, P. fluorescens 9AW and Pseudomonas putida 9BW, showed identical pyoverdine-related behaviour to each other, whereas the fifth strain, P. fluorescens 51W, had unique features compared to the other strains or to a set of 12 fluorescent Pseudomonas strains used as comparison material. Elucidation of the structure of the pyoverdines produced by the Antarctic strains supported the accuracy of the siderotyping methodology by confirming that pyoverdines from strains 1W and 10CW had the same structures as the P. fluorescens ATCC 13525 pyoverdine, whereas the 9AW and 9BW pyoverdines are probably identical with the pyoverdine of P. fluorescens strain 244. Pyoverdine from strain 51W appeared to be a novel pyoverdine since its structure was different from all previously established pyoverdine structures. Together with the conclusion that the Antarctic Pseudomonas strains have no special features at the level of their pyoverdines and pyoverdine-mediated iron metabolism compared to worldwide strains, the present work demonstrates that siderotyping provides a rapid means of screening for novel pyoverdines.

Use of siderophores to type pseudomonads: the three Pseudomonas aeruginosa pyoverdine systems.

Eighty-eight Pseudomonas aeruginosa isolates, most of them from the Collection of Bacterial Strains of the Institut Pasteur, Paris, were analysed for their pyoverdine-mediated iron incorporation system by different methods, including pyoverdine isoelectrofocusing analysis, pyoverdine-mediated growth stimulation, immunoblot detection of (ferri)pyoverdine outer-membrane receptor and pyoverdine-facilitated iron uptake. The same grouping of the strains was reached by each of these methods, resulting in the classification of the P. aeruginosa isolates, even those which were devoid of pyoverdine production, into three different siderophore types. Forty-two percent of the strains were identified with the type-strain P. aeruginosa ATCC 15,692 (group I), 42% were identical with the second type-strain P. aeruginosa ATCC 27,853 (group II) and 16% reacted identically with the clinical isolate P. aeruginosa Pa6, whose pyoverdine was recognized in this study to be identical in structure to the pyoverdine produced by a natural isolate, P. aeruginosa strain R. No new pyoverdine species was detected among these strains.