Mapping of mutations in Pseudomonas aeruginosa defective in pyoverdin production

Abstract

Twelve mutants of Pseudomonas aeruginosa PAO defective in pyoverdin production were isolated (after chemical and transposon mutagenesis) that were nonfluorescent and unable to grow on medium containing 400 ,uM ethylenediaminedi(o-hydroxyphenylacetic acid). Four mutants were unable to produce hydroxamate, six were hydroxamate positive, one was temperature sensitive for pyoverdin production, and another was unable to synthesize pyoverdin on succinate minimal medium but was capable of synthesizing pyoverdin when grown on Casamino Acids medium (Difco Laboratories, Detroit, Mich.). The mutations were mapped on the PAO chromosome. All the mutations affecting pyoverdin production were located at 65 to 70 min, between catAl and mtu-9002.Pathogenic bacteria require iron for growth in a mammalian host (6). To obtain iron from the host, bacteria must effectively compete with the iron-sequestering proteins transferrin and lactoferrin (1). Many microbes possess iron acquisition systems mediated by siderophores, lowmolecular-weight products capable of binding and delivering iron to the cell via high-affinity transport systems (31).Pseudomonas aeruginosa is a major cause of nosocomial infections which result in high mortality. P. aeruginosa is known to produce two siderophores, pyochelin (9, 10, 25) and pyoverdin (8,42). Pyochelin is a phenolic siderophore that has two sulfur-containing heterocyclic rings (9, 10). Pyoverdin, previously termed bacterial fluorescein (A. Turfreijer, Ph.D. thesis, University of Amsterdam, Amsterdam, The Netherlands, 1941), has long been thought to be involved in iron metabolism because of its hydroxamate character (16) and the inhibition of its production by iron (14,17,38). Only recently has the siderophore activity of pyoverdin been demonstrated (8) and its molecular structure elucidated (42). This fluorescent siderophore produced by P. aeruginosa is a complex peptide containing two hydroxamate groups and a dihydroxyquinoline derivative (42) as its theorized chelating moieties. Yellow-green fluorescent peptides produced by other fluorescent Pseudomonas species and Azotobacter vinelandii (5,15,28,32,33,37,44) have similar spectral characteristics and extensive structural homology with pyoverdin.Recent investigations have suggested that iron acquisition by P. aeruginosa may play a role in its pathogenesis. The concentration of iron in culture medium has a significant effect on the production of the extracellular proteins, toxin A, alkaline protease, and elastase (3, 4). Pyochelin has been shown to increase the lethality of P. aeruginosa during infections in mice (7). A mutant unable to synthesize pyoverdin had an extremely depressed growth rate compared with that of wild-type strains when grown in human serum and transferrin (2).Advances in P. aeruginosa genetics have allowed the map positions of several reported virulence factors to be determined. Use of the chromosome-mobilizing plasmid R68.45 * Corresponding author.(19), R-prime plasmids (21), and transposon-facilitated recombination (24) has m...

FptA, the Fe(III)-pyochelin receptor of Pseudomonas aeruginosa: a phenolate siderophore receptor homologous to hydroxamate siderophore receptors

“…In contrast, the transport genes for the fluorescent siderophores (pyoverdin/pseudobactin) are likely to have been recent acquisitions in the evolution of Pseudomonas rRNA homology group I. The P. aeruginosa pvd (3,32,61) and P. putida pvd (55) loci are located within the "catabolic-rich" regions of their respective genomes, and therefore the hypothesis that the genes for fluorescent siderophores are recent acquisitions in the evolution of Pseudomonas rRNA homology group I is in accord with the gene accretion model of pseudomonal genome evolution proposed by Holloway and Morgan (33).…”

Temperature-sensitive production of azoverdin, the pyoverdin-like sid rophore of Azomonas macrocytogenes ATCC 12334

“…The inability of micro-organisms to produce siderophores at slightly increased growth temperatures is a phenomenon previously encountered (Ankenbauer et al, 1986;Bachhawat & Ghosh, 1989;Garibaldi, 1971Garibaldi, ,1972Ismail et al, 1985;Marugg et al, 1985;Torres et al, 1986). The mechanism of temperature-regulated siderophore biosynthesis is not yet understood, although in Salmonella typhimurium, temperature-regulated siderophore production appears to function independently of thefur gene (Worsham & Konisky, 1984), suggesting the existence of another regulatory mechanism for siderophore production.…”

FvbA is required for vibriobactin utilization in Pseudomonas aeruginosa

“…It is known that strains of P. aeruginosa deficient in pyoverdine and pyochelin production fail to grow in ironlimited minimal medium containing the synthetic iron chelator EDDA, probably because they are incapable of utilizing EDDA-bound iron for growth (Ankenbauer et al, 1986). Based on this phenotype, we examined the ability of a P. aeruginosa mutant in siderophores production to grow in the presence of the V. cholerae siderophore vibriobactin and EDDA.…”