Development and application of an assay for uranyl complexation by fungal metabolites, including siderophores.
An assay to detect UO(2)(2+) complexation was developed based on the chrome azurol S (CAS) assay for siderophores (B. Schwyn and J. B. Neilands, Anal. Biochem. 160:47-56, 1987) and was used to investigate the ability of fungal metabolites to complex actinides. In this assay the discoloration of two dyed agars (one containing a CAS-Fe(3+) dye and the other containing a CAS-UO(2)(2+) dye) caused by ligands was quantified. The assay was tested by using the siderophore desferrioxamine B (DFO), and the results showed that there was a regular, reproducible relationship between discoloration and the amount of siderophore added. The ratio of the discoloration on the CAS-UO(2)(2+) agar to the discoloration on the CAS-Fe(3+) agar was independent of the amount of siderophore added. A total of 113 fungi and yeasts were isolated from three soil samples taken from the Peak District National Park. The fungi were screened for the production of UO(2)(2+) chelators by using the CAS-based assay and were also tested specifically for hydroxamate siderophore production by using the hydroxamate siderophore auxotroph Aureobacterium flavescens JG-9. This organism is highly sensitive to the presence of hydroxamate siderophores. However, the CAS-based assay was found to be less sensitive than the A. flavescens JG-9 assay. No significant difference between the results for each site for the two tests was found. Three isolates were selected for further study and were identified as two Pencillium species and a Mucor species. Our results show that the new assay can be effectively used to screen fungi for the production of UO(2)(2+) chelating ligands. We suggest that hydroxamate siderophores can be produced by mucoraceous fungi.
Renshaw
Joanna C
JC
Centre for Radiochemistry Research, Department of Chemistry, The University of Manchester, Manchester M13 9PT, United Kingdom. joanna.c.renshaw@man.ac.uk
Halliday
Verity
V
Robson
Geoffrey D
GD
Trinci
Anthony P J
AP
Wiebe
Marilyn G
MG
Livens
Francis R
FR
Collison
David
D
Taylor
Robin J
RJ
D000192:Actinomycetales / Q000254:growth & development / Q000378:metabolism; D003470:Culture Media; D003676:Deferoxamine / Q000378:metabolism*; D006877:Hydroxamic Acids / Q000378:metabolism; D062385:Hydroxybenzoates / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007202:Indicators and Reagents / Q000378:metabolism*; D008828:Microbiological Techniques; D009089:Mucor / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D010407:Penicillium / Q000145:classification / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D017262:Siderophores / Q000378:metabolism; D012988:Soil Microbiology; D014501:Uranium / Q000737:chemistry / Q000378:metabolism*
D003470:Culture Media; D006877:Hydroxamic Acids; D062385:Hydroxybenzoates; D007202:Indicators and Reagents; D017262:Siderophores; C015076:chrome azurol S; D014501:Uranium; D003676:Deferoxamine