Siderophore-mediated transport of molybdenum inAzospirillum lipoferum strain D-2

Saxena, Babita; Vithlani, Lina; Modi, V. V.

doi:10.1007/bf01570103

Cited by 15 publications

(9 citation statements)

References 16 publications

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“…Metallophores that have been previously classified as siderophores may be directly involved with regulation and uptake of Mo and V. Nitrogen-fixing bacteria, such as Cowpea Rhizobia (Patel et al 1988), Azospirilium lipoferum (Saxena et al 1989), and Azotobacter vinelandii (Cornish and Page 1995), are known to produce several catecholate and mixed-moiety siderophores. These organisms have a high nutritional requirement for Mo or V because of their utilization of these elements in nitrogenases, the key enzymes for N fixation (Bellenger et al 2008b;Kraepiel et al 2009).…”

Section: Iron Molybdenum and Vanadium In Nitrogen-fixing Bacteriamentioning

confidence: 99%

Metallophores and Trace Metal Biogeochemistry

et al. 2014

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Trace metal limitation not only affects the biological function of organisms, but also the health of ecosystems and the global cycling of elements. The enzymatic machinery of microbes helps to drive critical biogeochemical cycles at the macroscale, and in many cases, the function of metalloenzyme-mediated processes may be limited by the scarcity of essential trace metals. In response to these nutrient limitations, some organisms employ a strategy of exuding metallophores, biogenic ligands that facilitate the uptake of metal ions. For example, bacterial, fungal, and graminaceous plant species are known to use Fe(III)-binding siderophores for nutrient acquisition, providing the best known and most thoroughly studied example of metallophores. However, recent breakthroughs have suggested or established the role of metallophores in the uptake of several other metallic nutrients. Furthermore, these metallophores may influence environmental trace metal fate and transport beyond nutrient acquisition. These discoveries have resulted in a deeper understanding of trace metal geochemistry and its relationship to the cycling of carbon and nitrogen in natural systems. In this review, we provide an overview of the current state of knowledge on the biogeochemistry of metallophores in trace metal acquisition, and explore established and potential metallophore systems.Electronic supplementary material The online version of this article (

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Section: Iron Molybdenum and Vanadium In Nitrogen-fixing Bacteriamentioning

confidence: 99%

Metallophores and Trace Metal Biogeochemistry

et al. 2014

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“…They indicated that tungsten could not dissociate the rnolybdenum-siderophore conjugate. Azospiri1lum lipoferum secreted a related compound (3,5-dihydroxybenzoic acid) under both mOlybdenum-lirnited as weIl as rnolybdenum-supplernented conditions (Saxena et al 1989). These workers stated that molybdenum was coordinated wi ~!l 3, 5-DHBA, which enhanced molybdenurn up _ake.…”

Section: Molybdenum Uptake and Transportmentioning

confidence: 99%

“…Accordingly soil bacteria have developed specific, high affinity systems for processing molybdenum. Bacillus thuringiensis, cowpea Rhizobium, and Azospirillum lipoferum secrete catechol derivative siderophores that mediate the transport of molybdenum (Ketchum and Owen 1975, Saxena et al 1989.…”

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confidence: 99%

Effect of tungsten on nitrate and nitrite reductases in Azospirillum brasilense Sp7

Chauret¹,

Knowles²

1991

Can. J. Microbiol.

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Tungstate, at concentrations that completely suppressed nitrate reductase activity in Paracoccus denitrificans, caused only partial inhibition of nitrate reductase in Azospirillum brasilense Sp7. Nitrate reductase activity in cell-free extracts was much more sensitive than whole cells to tungstate, suggesting that there may be a barrier to its transport. Nitrite reductase activity was partially inhibited by tungstate in both whole cells and cell-free extracts. Azospirillum brasilense apparently scavenged enough contaminating molybdenum from molybdenum-limited medium to allow maximum nitrate reductase activity, which was not stimulated by added molybdate. Cells grown in molybdenum-depleted medium could not reduce nitrate. Nitrate concentrations less than 0.25 mM inhibited activity, but not synthesis, of nitrite reductase and caused significant accumulation of nitrite during reduction of nitrate. Key words: Azospirillum brasilense, Paracoccus denitrificans, nitrate reductase, nitrite reductase, tungsten, molybdenum, denitrification.

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“…In the presence of a low molybdenum concentration, catecholate-like molybdate-coordinating compounds may be formed by a number of microorganisms. However, it is not clear whether these compounds are dedicated, true mediators of high-affinity molybdate uptake or are simply misidentified members of a high-affinity iron uptake system (20,32,35).…”

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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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Siderophore-mediated transport of molybdenum inAzospirillum lipoferum strain D-2

Cited by 15 publications

References 16 publications

Metallophores and Trace Metal Biogeochemistry

Metallophores and Trace Metal Biogeochemistry

Effect of tungsten on nitrate and nitrite reductases in Azospirillum brasilense Sp7

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

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