Characterization of pyoverdins secreted by a subsurface strain of Pseudomonas fluorescens and their interactions with uranium(VI)

Fluorescent Pseudomonas species secrete pyoverdin-type siderophores with a high potential to dissolve, bind, and thus transport uranium in the environment. The formation of complexes of UO2 2 + with pyoverdins released by the groundwater bacterium Pseudomonas fluorescens (CCUG 32456) isolated at a depth of 70 m in the Aspo Hard Rock Laboratory, Sweden, was studied. Mass spectrometry indicated that the cells produce a pyoverdin–mixture with four main components: pyoverdin with a succinamide side chain, pyoverdin with a succinic acid side chain, ferribactin with a succinamide side chain, and ferribactin with a glutamic acid side chain. Three pK values could be determined from the pH-dependent changes in the absorption spectra of the pyoverdin mixture: log s012 = 22.67 ± 0.15 (pK1 = 4.40), log s013 = 29.15 ± 0.05 (pK2 = 6.48), and log s014 = 33.55 ± 0.05 (pK3 = 10.47). The fluorescence properties of the pyoverdin mixture were pH-dependent. The emission maximum changed from 448 nm at pH = 2.1 to 466 nm in the...