Abstract:From Pseudomonas chlororaphis D-TR 133 a pyoverdine was isolated and its primary structure were elucidated by spectroscopic methods and degradation reactions. Despite some structural differences, its Fe(III) complex and that of the pyoverdine from Pseudomonas fluorescens CHA0 were taken up by either strain with a high rate. This is explained by a structural similarity between the two pyoverdines which were shown to differ in their structures only by the replacement of Lys by Ala in the C-terminal part of the m… Show more
“…Instead, P. fluorescens very likely utilizes the S. ambofaciens siderophores desferrioxamine B and coelichelin as xenosiderophores, thanks to its FoxA receptor. In contrast to most studies, in which the use of xenosiderophores was revealed indirectly through the addition of purified siderophore to the growth medium (44)(45)(46)(47), binding affinity assays (11,48), or native PAGE and surface plasmon resonance (49) or with labeled iron (11,50,51), we revealed potential iron piracy through a direct interaction between a Gram-positive and a Gram-negative bacterium. This potential piracy likely occurs only in one direction.…”
Iron is essential in many biological processes. However, its bioavailability is reduced in aerobic environments, such as soil. To overcome this limitation, microorganisms have developed different strategies, such as iron chelation by siderophores. Some bacteria have even gained the ability to detect and utilize xenosiderophores, i.e., siderophores produced by other organisms. We illustrate an example of such an interaction between two soil bacteria, Pseudomonas fluorescens strain BBc6R8 and Streptomyces ambofaciens ATCC 23877, which produce the siderophores pyoverdine and enantiopyochelin and the siderophores desferrioxamines B and E and coelichelin, respectively. During pairwise cultures on iron-limiting agar medium, no induction of siderophore synthesis by P. fluorescens BBc6R8 was observed in the presence of S. ambofaciens ATCC 23877. Cocultures with a Streptomyces mutant strain that produced either coelichelin or desferrioxamines, as well as culture in a medium supplemented with desferrioxamine B, resulted in the absence of pyoverdine production; however, culture with a double mutant deficient in desferrioxamines and coelichelin production did not. This strongly suggests that P. fluorescens BBbc6R8 utilizes the ferrioxamines and ferricoelichelin produced by S. ambofaciens as xenosiderophores and therefore no longer activates the production of its own siderophores. A screening of a library of P. fluorescens BBc6R8 mutants highlighted the involvement of the TonB-dependent receptor FoxA in this process: the expression of foxA and genes involved in the regulation of its biosynthesis was induced in the presence of S. ambofaciens. In a competitive environment, such as soil, siderophore piracy could well be one of the driving forces that determine the outcome of microbial competition.
Bacteria detect, assimilate, and integrate different environmental signals in order to better adapt to their habitat and cope with changes in environmental conditions. Multiple signaling pathways allow them to communicate with each other within the same species or between different species (1). This can be achieved through the production and detection of diffusible molecules in the environment. In response to these interactions, the microorganisms have developed complex metabolic and physiological responses. One of the essential environmental factors vital for organisms is iron. It plays an essential role in many biological processes, such as DNA synthesis, respiration, and photosynthesis. Iron can adopt two different ionic forms, Fe 2ϩ and Fe 3ϩ . This property makes it an important player in the oxidation-reduction reactions in the cell. However, while iron is an abundant element on earth, its bioavailability is reduced in aerobic environments, such as soil. Ferric iron (Fe 3ϩ ) forms insoluble ferric hydroxides (with a solubility product of ϳ10 Ϫ39 ) in the presence of oxygen (2-4). Therefore, iron is a limiting factor for the growth of microorganisms.To overcome the limitation of iron bioavailability, aerobic bacteria have develop...
“…Instead, P. fluorescens very likely utilizes the S. ambofaciens siderophores desferrioxamine B and coelichelin as xenosiderophores, thanks to its FoxA receptor. In contrast to most studies, in which the use of xenosiderophores was revealed indirectly through the addition of purified siderophore to the growth medium (44)(45)(46)(47), binding affinity assays (11,48), or native PAGE and surface plasmon resonance (49) or with labeled iron (11,50,51), we revealed potential iron piracy through a direct interaction between a Gram-positive and a Gram-negative bacterium. This potential piracy likely occurs only in one direction.…”
Iron is essential in many biological processes. However, its bioavailability is reduced in aerobic environments, such as soil. To overcome this limitation, microorganisms have developed different strategies, such as iron chelation by siderophores. Some bacteria have even gained the ability to detect and utilize xenosiderophores, i.e., siderophores produced by other organisms. We illustrate an example of such an interaction between two soil bacteria, Pseudomonas fluorescens strain BBc6R8 and Streptomyces ambofaciens ATCC 23877, which produce the siderophores pyoverdine and enantiopyochelin and the siderophores desferrioxamines B and E and coelichelin, respectively. During pairwise cultures on iron-limiting agar medium, no induction of siderophore synthesis by P. fluorescens BBc6R8 was observed in the presence of S. ambofaciens ATCC 23877. Cocultures with a Streptomyces mutant strain that produced either coelichelin or desferrioxamines, as well as culture in a medium supplemented with desferrioxamine B, resulted in the absence of pyoverdine production; however, culture with a double mutant deficient in desferrioxamines and coelichelin production did not. This strongly suggests that P. fluorescens BBbc6R8 utilizes the ferrioxamines and ferricoelichelin produced by S. ambofaciens as xenosiderophores and therefore no longer activates the production of its own siderophores. A screening of a library of P. fluorescens BBc6R8 mutants highlighted the involvement of the TonB-dependent receptor FoxA in this process: the expression of foxA and genes involved in the regulation of its biosynthesis was induced in the presence of S. ambofaciens. In a competitive environment, such as soil, siderophore piracy could well be one of the driving forces that determine the outcome of microbial competition.
Bacteria detect, assimilate, and integrate different environmental signals in order to better adapt to their habitat and cope with changes in environmental conditions. Multiple signaling pathways allow them to communicate with each other within the same species or between different species (1). This can be achieved through the production and detection of diffusible molecules in the environment. In response to these interactions, the microorganisms have developed complex metabolic and physiological responses. One of the essential environmental factors vital for organisms is iron. It plays an essential role in many biological processes, such as DNA synthesis, respiration, and photosynthesis. Iron can adopt two different ionic forms, Fe 2ϩ and Fe 3ϩ . This property makes it an important player in the oxidation-reduction reactions in the cell. However, while iron is an abundant element on earth, its bioavailability is reduced in aerobic environments, such as soil. Ferric iron (Fe 3ϩ ) forms insoluble ferric hydroxides (with a solubility product of ϳ10 Ϫ39 ) in the presence of oxygen (2-4). Therefore, iron is a limiting factor for the growth of microorganisms.To overcome the limitation of iron bioavailability, aerobic bacteria have develop...
“…To develop future analytical tools, with fast throughput as in plate-reader technology, it would be desirable to separate between the optical signaling of metal coordination and the surface-adhesive moiety. It occurred to us that, like in the siderophores of the pyoverdin family, − the iron(III) binding site could be fused with a fluorescent probe into a single functionality (Figure ). 1 Fluorescent bidentate 2,3-diamino-6,7-dihydroxy-quinoline binding units (a) of pyoverdin PaA 40 and (b) of azotobactin δ …”
In the quest for fast throughput metal biosensors, it would be of interest to prepare fluorophoric ligands with surface-adhesive moieties. Biomimetic analogues to microbial siderophores possessing such ligands offer attractive model compounds and new opportunities to meet this challenge. The design, synthesis, and physicochemical characterization of biomimetic analogues of microbial siderophores from Paracoccus denitrificans and from the Vibrio genus are described. The (4S,5S)-2-(2-hydroxyphenyl)-5-methyl-4,5-dihydro-1,3-oxazole-4-carbonyl group (La), noted here as an HPO unit, was selected for its potential dual properties, serving as a selective iron(III) binder and simultaneously as a fluorophore. Three tripodal symmetric analogues cis-Lb, cis-Lc, and trans-Lc, which mainly differ in the length of the spacers between the central carbon anchor and the ligating sites, were synthesized. These ferric-carriers were built from a tetrahedral carbon as an anchor, symmetrically extended by three converging iron-binding chains, each bearing a terminal HPO. The fourth chain could contain a surface-adhesive function (Lc). A combination of absorption and emission spectrophotometry, potentiometry, electrospray mass spectrometry, and electrochemistry was used to fully characterize the corresponding ferric complexes and to determine their stability. The quenching mechanism is consistent with an intramolecular static process and is more efficient for the analogue with longer arms. Detection limits in the low nanogram per milliliter range, comparable with the best chemosensors based on natural peptide siderophores, have been determined. These results clearly demonstrate that these tris(phenol-oxazoline) ligands in a tripodal arrangement firmly bind iron(III). Due to their fluorescent properties, the coordination event can be easily monitored, while the fourth arm is available for surface-adhesive moieties. The tripodal system is therefore an ideal candidate for integration with solid-state materials for the development of chip-based devices and analytical methodologies.
“…One instance is the production of a pyoverdine siderophore with two structural variants, whose amino acid structure differs in the incorporation of alanine or glycine [30]. However, the substitution of glycine was restricted to a specific alanine residue in the siderophore and the glycine-containing siderophore was a minor portion of the total siderophore production and could not be independently isolated.…”
Section: Discussionmentioning
confidence: 99%
“…The NRPS-dependent biosynthetic pathways of a number of siderophores have been well studied, including enterobactin [24–26], pyochelin [27], yersiniabactin [28], vibriobactin [29], mycobactins [15], and pyoverdine [30, 31]. The amphiphilic peptidic marine siderophores are likely also assembled by NRPS multienzyme systems due to the inclusion of unique features such as D-amino acids, N-terminally attached fatty acid chains, and heterocyclic elements [23, 32].…”
In response to iron deplete aerobic conditions, bacteria often secrete low molecular weight, high-affinity iron(III)-complexing ligands, siderophores, to solubilize and sequester iron(III). Many marine siderophores are amphiphilic and are produced in suites, wherein each member within a particular suite has the same iron(III)-binding polar head group which is appended by one or two fatty acids of varying length, degree of unsaturation and hydroxylation, establishing the suite composition. We report herein the isolation and structural characterization of a suite of siderophores from marine bacterial isolate Vibrio sp. Nt1. Based on structural analysis, this suite of siderophores, the moanachelins, is amphiphilic and composed of two N-acetyl, N-hydroxy D-ornithines, one N-acetyl, N-hydroxy L-ornithine and either a glycine or an L-alanine, appended with various saturated and unsaturated fatty acid tails. The variation in the small side-chain amino acid is the first occurrence of variation in the peptidic head group structure of a set of siderophores produced by a single bacterium.
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