Layer plate CAS assay for the quantitation of siderophore production and determination of exudation patterns for fungi

The chrome azurol S (CAS) assay measures the chelating activity of siderophores, but its application (especially to fungi) is limited by toxicity issues. In this note, we describe a modified version of the CAS assay that is suitable for quantifying siderophore exudation for microorganisms, including fungi. [Display omitted] •Modified CAS layer plates have reduced toxicity, making them suitable for fungi.•Method allows visual and quantitative comparison of siderophore exudation.•Siderophore exudation by fungi on CAS layer plates can be quantified as function of time.