Table 2.

Growth of Fpv⁻ mutants of Pf-5 on an iron-limited medium in the presence of specific pyoverdines

Peptide chain composition of pyoverdine testeda	Source strain of pyoverdine	Pyoverdine preparationb	Growth of Pf-5 deletion mutantc:
			fpvZ	fpvU	fpvY	fpvW	fpvX	fpvV
Asp-FOHOrn-Lys-(Thr-Ala-Ala-FOHOrn-Lys)	P. protegens Pf-5	Partially purified	−	+	+	+	+	+
		Purified	−	+	+	+	+	+
Ser-Arg-Ser-FOHOrn-(Lys-FOHOrn-Thr-Thr) (type I pyoverdine)	P. aeruginosa PAO1	Partially purified	+	−	+	+	+	+
		Pyoverdine D	+	−	+	+	+	+
		Pyoverdine C	+	−	+	+	+	+
Ser-Lys-Gly-FOHOrn-(Lys-FOHOrn-Ser)	P. fluorescens ATCC 13525	Partially purifiedd	+	−	+	+	+	+
Ser-Lys-FOHOrn-Ser-Ser-Gly-(Lys-FOHOrn-Ser-Ser)	P. rhodesiae CFML92-104	Partially purified	+	+	−	+	+	+
		Purified	+	+	−	+	+	+
εLys-OHAsp-Ala-aThr-Ala-cOHOrn	Pseudomonas sp. B10	Partially purified	+	+	+	−	+	+
		B10-1034	+	+	+	−	+	+
		B10-1018	+	+	+	−	+	+
		Pseudobactin	+	+	+	−	+	+
Ala-Lys-Thr-Ser-AOHOrn-cOHOrn	Pseudomonas sp. SB8.3	Partially purified	+	+	+	+	−	+
		Purified	+	+	+	+	−	+
Unknown	P. putida Bn7	Partially purified	+	+	+	+	+	−
		Bn7-1162	+	+	+	+	+	−
		Bn7-1046	+	+	+	+	+	−
		Bn7-1133	+	+	+	+	+	−
Ser-FOHOrn-Orn-Gly-aThr-Ser-cOHOrn (type II pyoverdine)	P. aeruginosa ATCC 27853	Partially purified	+	+	+	+	+	+
Ser-FOHOrn-Orn-Gly-aThr-Ser-cOHOrn (type II pyoverdine)	P. aeruginosa 7NSK2	Partially purified	+	+	+	+	+	+

^aUnderline denotes a d-amino acid. Parentheses define cyclic residues. cOHOrn, cyclo-hydroxy-ornithine; εLys, Lys linked by its ε-NH₂; OHAsp, threo-β-hydroxy-aspartic acid; aThr, allo-Thr. Italicized structures were predicted by siderotyping and lack stereochemistry (Table 1).

^bPartially purified pyoverdines were obtained following liquid chromatography of culture supernatants from the designated strains of Pseudomonas spp. Purified samples were obtained following HPLC fractionation of the partially purified samples. Structures of purified pyoverdines were determined by high-resolution ESI-MS (see Text S1 in the supplemental material), and m/z values were consistent with the peptide chain, as shown in all cases. Acyl side chains for the pyoverdine isoforms were identified as follows: P. aeruginosa PAO1, pyoverdine C (α-ketoglutaric acid) and pyoverdine D (succinic acid) (71); Pseudomonas sp. B10, pseudobactin (succinic acid) (36), B10-1018 (possibly glutamic acid), and B10-1034 (possibly a hydroxylated congener of B10-1018 [e.g., OH-glutamate, 5-OH-chromophore, exchange of Ala with Ser]). The structure of the pyoverdine produced by P. putida Bn7 is unknown, and high-resolution ESI-MS analysis revealed three isoforms with [M + H]⁺ ions at m/z 1,163.4956, 1,047.441 and 1,134.4751. The difference of 29 mass units between Bn7-1133 and Bn7-1162 may correspond to acyl side chains composed of succinic acid and glutamic acid, respectively.

^cGrowth of Fpv⁻ mutants in a ΔpvdI-pchA background of Pf-5 on an iron-limited medium (KMB amended with 600 μM 2,2′-dipyridyl) in the presence of the pyoverdine sample: +, growth; −, no growth. The ΔpvdI-pchA mutant of Pf-5 did not grow on the iron-limited medium in isolation but did grow in the presence of all pyoverdine samples listed. Values represent results from two replicate plates in each of two experiments evaluating each partially purified sample. Purified isoforms were evaluated in only one experiment due to the limited amounts available.

^dThe pyoverdine from ATCC 13525 was a gift from Isabelle Schalk and Valérie Geoffroy.