Fitness in soil and rhizosphere of Pseudomonas fluorescens C7R12 compared with a C7R12 mutant affected in pyoverdine synthesis and uptake

Abstract

Fluorescent pseudomonads have evolved an efficient strategy of iron uptake based on the synthesis of the siderophore pyoverdine and its relevant outer membrane receptor. The possible implication of pyoverdine synthesis and uptake on the ecological competence of a model strain (Pseudomonas fluorescens C7R12) in soil habitats was evaluated using a pyoverdine minus mutant (PL1) obtained by random insertion of the transposon Tn5. The Tn5 flanking DNA was amplified by inverse PCR and sequenced. The nucleotide sequence was found to show a high level of identity with pvsB, a pyoverdine synthetase. As expected, the mutant PL1 was significantly more susceptible to iron starvation than the wild-type strain despite its ability to produce another unknown siderophore. As with the wild-type strain, the mutant PL1 was able to incorporate the wild-type pyoverdine and five pyoverdines of foreign origin, but at a significantly lower rate despite the similarity of the outer membrane protein patterns of the two strains. The survival kinetics of the wild-type and of the pyoverdine minus mutant, in bulk and rhizosphere soil, were compared under gnotobiotic and non-gnotobiotic conditions. In gnotobiotic model systems, both strains, when inoculated separately, showed a similar survival in soil and rhizosphere, suggesting that iron was not a limiting factor. In contrast, when inoculated together, the bacterial competition was favorable to the pyoverdine producer C7R12. The efficient fitness of PL1 in the presence of the indigenous microflora, even when coinoculated with C7R12, is assumed to be related to its ability to uptake heterologous pyoverdines. Altogether, these results suggest that pyoverdine-mediated iron uptake is involved in the ecological competence of the strain P. fluorescens C7R12.

Burkholderia spp. Alter Pseudomonas aeruginosa Physiology through Iron Sequestration

“…This suggests that, in some environments where the two species are in similar (50). Siderophores are important for microbial growth in the soil and have been isolated directly from soil in several studies (4,32). In addition, P. aeruginosa siderophores have been isolated from the sputa of CF patients (16).…”

The sensor kinase PhoQ mediates virulence in Pseudomonas aeruginosa

“…0.2 M HCl before measurement at 520 nm (Mavrodi et al, 2001;Whooley & McLoughlin, 1982). For pyoverdine measurements, supernatants were diluted 1/70 to 1/100 in 10 mM Tris/HCl pH 7.5 and excited at 400 nm with a spectrofluorimeter (Baysse et al, 2002;Mirleau et al, 2000). Lipase secretion was determined by enzymic assay according to Furutani et al (1995).…”

Effect of <i>Pseudomonas fluorescens</i> inoculation on the improvement of iron deficiency in tomato

“…The pyoverdines are characteristic siderophores (1000-1500 Da), composed of three structural parts: dihydroxyquinoline chromophores responsible for fluorescence; a variable peptide part composed of 6-12 amino acids; and a side chain (Meyer 2000, Cornelis andMatthijs 2002). The low biological availability of iron in the soil is improved by the use of P. fluorescens (Loper and Henkels 1999), and the pyoverdine-conferred iron uptake from the rhizosphere (Mirleau et al 2000, Mirleau et al 2001.…”