Siderophores in forest soil solution

Siderophores in soil solution of coniferous forest soils have been chemically identified for the first time. We have identified the siderophores ferrichrome and ferricrocin in soil solution of the upper organic layer by High Performance Liquid Chromatography (HPLC) Mass Spectrometry (MS). The soil solutions were sampled from mor layers of podzolic soils from the south and the north of Sweden and from a mor layer overlying granitic rock and intensively colonised by ectomycorrhizal hyphae. Ferrichrome was found in nanomolar concentrations in all soil solutions investigated and ferricrocin only in the soil solution from the mor layer covering a rock and in the soil solution from the north of Sweden. The findings are discussed in relation to the possible role of fungal hyphae and siderophores in weathering minerals in podzolic soils under coniferous forests. Citric and oxalic acid are able to dissolve minerals via complexation of cations from the mineral. Siderophores should be, kinetically and thermodynamically, even more efficient complexing agents for trivalent cations than oxalic and citric acid. The present study provides direct evidence for the presence of siderophores in soil solution.