Methods for the detection of Pseudomonas siderophores

The potentials of different testing methods for detecting the production of siderophores (universal chemical assay (CAS-agar assay), absorption spectrum, bioassay) were investigated. Twelve strains (5 species) of the genus Pseudomonas, including known siderophore producers and wild natural isolates, were included in the study. Combination of different methods to detect the production of bacterial siderophores provided more information than when using e.g. the CAS-agar assay alone. The bioassay was useful when the specificity of siderophores and their affinity for iron were investigated. Negative results in the CAS-agar assay and in absorption spectrum studies did not mean that competitive ligands against ethylenediamine-di-(o-hydroxyphenyl) acetic acid (EDDA) could not be produced, as was observed in the bioassay. The use of more than one test is essential when selecting bacterial strains for agroindustrial applications such as plant disease control.