Siderophores fungi

The po.ssible role of a chelate reductase for iron uptake from microbial siderophores has been examined for several plant species (30,47). With certain microbial siderophores such as rhizoferrin and rhodotorulic acid, the reductase may easily cleave iron from the siderophore to allow subsequent uptake by the ferrous iron transporter. However, with the hydroxamate siderophore, ferrioxamine B, which is produced by actinomycetes and u.sed by diverse bacteria and fungi, it has been shown that the iron stress-regulated reductase is not capable... 

Siderophores are iron-complexing compounds of low molecular weight that are synthesized by bacteria and fungi, and serve to deliver iron to the microbes. Because of their exclusive affinity and specificity for Fe3+, natural siderophores and synthetic derivatives have been exploited in the treatment of human iron-overload diseases. The most successfully used example is Desferal , which is the methane sulfonate derivative of iron-free ferrioxamine B, a linear trihydroxamate (Figure 3.2). Ferrioxamine was isolated in 1958 from the culture supernatant of Streptomyces... 

In common with most prokaryotes many fungi have siderophore-dependent iron uptake systems. The ferrichrome-type siderophores are often employed, although other types of siderophore are also used. Indeed, even if, like the quintessential scavenger baker s yeast (S. cerevisiae), they produce no siderophores of their own, they nonetheless have several... 

There is only a small selection of nonprotein amino acids that contain carbonyl groups in the form of ketone, aldehyde, and carboxylic acid moieties, as part of the side chain. The examples given in Table 6 are components of nonribosomal peptides isolated from bacteria or fungi and siderophores from bacteria. The biosynthesis of these amino acids is not clear however, some of the amino acids with carboxylic acid side chains may be traced back to the L-a-amino acids aspartic acid and glutamic acid. 

Haselwandter K, Dobemigg B, Beck W, Jung G, Cansier A, Winkelmann G (1992) Isolation and Identification of Hydroxamate Siderophores of Ericoid Mycorrhizal Fungi. BioMetals 5 51... 

Holinsworth B, Martin JD (2009) Siderophore Production by Marine-derived Fungi. Biometals 22 625... 

Huschka HG, Jalal MAP, van der Helm D, WinkelmannG (1986) Molecular Recognition of Siderophores in Fungi Role of Iron-surrounding V-Acyl Residues and the Peptide Backbone During Membrane Transport in Neurospora crassa. J Bacteriol 167 1020... 

Jalal MAF, Love SK, van der Hehn D (1988) A -Dhnethylcoprogens. Three Novel Trihydroxamate Siderophores from Pathogenic Fungi. Biol Metals 1 4... 

Konetschny-Rapp S, Huschka HG, Winkehnann G, Jung G (1988) High-performance Liquid Chromatography of Siderophores from Fungi. Biol Metals 1 9... 

Mtinzinger M, Taraz K, Budzikiewicz H, Drechsel H, Heymann P, Winkelmann G, Meyer JM (1999). S,S-Rhizoferrin (enantio-rhizoferrin) a Siderophore of Ralstonia (Pseudomonas) pickettii DSM 6297 - the Optical Antipode of R,R-Rhizoferrin Isolated from Fungi. BioMetals 12 189... 

Winkelmann G, Huschka HG (1989) Molecular Recognition and Transport of Siderophores in Fungi. In Winkelmann G, van der Hehn D, Neilands JB (eds) Iron Transport in Microbes, Plants and Animals. VCH, Weinheim, p 317... 

General mineral nutrition status improvement for the host plant has been studied frequently to understand the roles of endophytic fungi. Iron nutrition, however, has been studied only occasionally. P. fortinii strains obtained from Pinus sylvestris, Abies alba, Picea abies, and Carex curvula (the last a monocotyledonous plant) were found to produce the cyclic hexapeptide siderophores ferricrocin (73), ferrirubin (74) and ferrichrome C (75). The concentration and pattern of siderophore production was dependent on ferric ion concentration, pH of the medium, and the strain of endophyte. 

Haselwandter K etal, Isolation and identification of hydroxamate siderophores of ericoid mycorrhizal fungi, BioMetals 5 51-56, 1992. 

When deficient in iron, bacteria and fungi produce and excrete to the extracellular medium low molecular weight, specific iron-carrier molecules, called siderophores. These siderophores bind ferric ions, to form soluble complexes. The complexed ferric ions are transported into the cell through high-affinity and energy-dependent receptor proteins located on the outer membrane. In Gram-negative bacteria, such as E. coli, the most studied system, siderophore-iron complexes are transported initially to the periplasm. 

Ferrichrome was the first siderophore to be isolated and characterized from the fungi Ustilago sphaerogena in 1952. It is a cyclic hexapeptide with the sequence cycto[(Gly)3-(Al -acetyl-Af -hydroxy-L-ornithine)3] (1) . The biologically active ferrichromes form iron(ni) complexes with a left-handed A-cis helical twist. 

Jalal, M. A. F., Love, S. K., and van der Helm, D. (1988). Af -Dimethylcoprogens. Three novel trihydroxamate siderophores from pathogenic fungi. Biol. Met. 1,4-8. 

Escherichia coli has at least five independent transport systems, one of which is the low affinity pathway described above. In addition, it synthesizes enterobactin as a siderophore it can take up the iron(III) complex of ferrichrome, a siderophore synthesized by certain fungi there is a citrate-induced system, and a less common process involving aerobactin. 

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