The stability of the molybdenum-azotochelin complex and its effect on siderophore production in Azotobacter vinelandii

Duhme, Anne-Kathrin; Hider, Robert C.; Naldrett, Mike J.; Pau, Richard N.

doi:10.1007/s007750050263

Cited by 60 publications

(56 citation statements)

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“…Visca et al (1992) suggested that PCH could play a role in the acquisition of metals other than Fe(III), such as Co(II) and Mo(VI). Likewise, azotochelin, a catecholate siderophore, has been suggested to participate in the uptake of molybdenum by Azotobacter vinelandii (Duhme et al, 1998). …”

Section: Discussionmentioning

confidence: 99%

Vanadium interferes with siderophore-mediated iron uptake in Pseudomonas aeruginosa

et al. 2000

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Vanadium is a metal that under physiological conditions can exist in two oxidation states, V(IV) (vanadyl ion) and V(V) (vanadate ion).Here, it was demonstrated that both ions can form complexes with siderophores. Pseudomonas aeruginosa produces two siderophores under iron-limiting conditions, pyoverdine (PVD) and pyochelin (PCH). Vanadyl sulfate, at a concentration of 1-2 mM, strongly inhibited growth of P. aeruginosa PAO1, especially under conditions of severe iron limitation imposed by the presence of non-utilizable Fe(III) chelators. PVD-deficient mutants were more sensitive to vanadium than the wild-type, but addition of PVD did not stimulate their growth. Conversely, PCH-negative mutants were more resistant to vanadium than the wild-type strain. Both siderophores could bind and form complexes with vanadium after incubation with vanadyl sulfate (1 :1, in the case of PVD ; :1, in the case of PCH). Although only one complex with PVD, V(IV)-PVD, was found, both V(IV)-and V(V)-PCH were detected. V-PCH, but not V-PVD, causedstrong growth reduction, resulting in a prolonged lag phase. Exposure of PAO1 cells to vanadium induced resistance to the superoxide-generating compound paraquat, and conversely, exposure to paraquat increased resistance to V(IV). Superoxide dismutase (SOD) activity of cells grown in the presence of V(IV) was augmented by a factor of two. Mutants deficient in the production of Fe-SOD (SodB) were particularly sensitive to vanadium, whilst sodA mutants deficient for Mn-SOD were only marginally affected. In conclusion, it is suggested that V-PCH catalyses a Fenton-type reaction whereby the toxic superoxide anion O N 2 is generated, and that vanadium compromises PVD utilization.

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Section: Discussionmentioning

confidence: 99%

Vanadium interferes with siderophore-mediated iron uptake in Pseudomonas aeruginosa

et al. 2000

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“…The cells must be iron limited to form catecholate siderophores, yet high-affinity molybdate transport operates well in iron-sufficient medium (26). Duhme et al (10) suggested that protochelin replaces azotochelin in medium containing molybdate at a concentration of 70 M or more, because azotochelin is depleted during high-affinity molybdate transport. However, high-affinity molybdate transport in A. vinelandii is repressed in the presence of 10 M molybdate (26).…”

Section: Discussionmentioning

confidence: 99%

Role of Molybdate and Other Transition Metals in the Accumulation of Protochelin by Azotobacter vinelandii

Cornish

Page

2000

Appl Environ Microbiol

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Both molybdate and iron are metals that are required by the obligately aerobic organism Azotobacter vinelandii to survive in the nutrient-limited conditions of its natural soil environment. Previous studies have shown that a high concentration of molybdate (1 mM) affects the formation of A. vinelandii siderophores such that the tricatecholate protochelin is formed to the exclusion of the other catecholate siderophores, azotochelin and aminochelin. It has been shown previously that molybdate combines readily with catecholates and interferes with siderophore function. In this study, we found that the manner in which each catecholate siderophore interacted with molybdate was consistent with the structure and binding potential of the siderophore. The affinity that each siderophore had for molybdate was high enough that stable molybdosiderophore complexes were formed but low enough that the complexes were readily destabilized by Fe 3؉ . Thus, competition between Fe 3؉ and molybdate did not appear to be the primary cause of protochelin accumulation; in addition, we determined that protochelin accumulated in the presence of vanadate, tungstate, Zn 2؉ , and Mn 2؉ . We found that all five of these metal ions partially inhibited uptake of 55 Fe-protochelin and 55 Feazotochelin complexes. Also, each of these metal ions partially inhibited the activity of ferric reductase, an enzyme important in the deferration of ferric siderophores. Our results suggest that protochelin accumulates in the presence of molybdate because protochelin uptake and conversion into its component parts, azotochelin and aminochelin, are inhibited by interference with ferric reductase.

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“…Baysse et al (2000) reported the repression of pyoverdin production by vanadium and explained that uptake of several metals by siderophores was possible. Duhme et al (1998) have also demonstrated that catecholate siderophores have been suggested to participate in molybdenum acquisition. These results are encouraging as they suggest it is possible to utilise bacteria to protect and stimulate plant growth in soils which are polluted with pesticides and agrochemicals (Vivas et al, 2003).…”

Section: Effect Of Bacterial Growth Inhibitors On Siderophore Productionmentioning

confidence: 95%

Effect of iron and growth inhibitors on siderophores production by Pseudomonas fluorescens

Rachid¹,

Bensoltane²

2005

Afr. J. Biotechnol.

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The ability of Pseudomonas to grow and to produce siderophores is dependent on the iron content and the type of carbon sources in the medium. Under conditions of low-iron concentration the Pseudomonas isolates studied produced yellow-green fluorescent iron-binding peptide siderophores and the biosynthesis of this siderophores was affected by several different environmental parameters. Four basal media, supplemented with different concentration of iron, were employed to study the effect of iron and different organic carbon sources on siderophore production in Pseudomonas fluorescens. The highest siderophores concentration was obtained in succinate medium. Ferric iron increased the growth yield and completely repressed siderophores production above 200 g/l, but had a positive effect below 160 g/l. Penicillin and lead elicited the production of siderophores in the presence of excess iron. Pre-treatment of the standard succinate medium with α α α α,α α α α-dipyridyl and 8-hydroxyquinoline to reduce the concentration of iron diminished both the growth yield and siderophore production, but α α α α,α α α α-dipyridyl increased significantly the amount of siderophores produced in the presence of 0.20 mg/l of the chelating ion.

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The stability of the molybdenum-azotochelin complex and its effect on siderophore production in Azotobacter vinelandii

Cited by 60 publications

References 1 publication

Vanadium interferes with siderophore-mediated iron uptake in Pseudomonas aeruginosa

Vanadium interferes with siderophore-mediated iron uptake in Pseudomonas aeruginosa

Role of Molybdate and Other Transition Metals in the Accumulation of Protochelin by Azotobacter vinelandii

Effect of iron and growth inhibitors on siderophores production by Pseudomonas fluorescens

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