Fig. 1.

Colorimetric plate phosphatase assays. (A) DP4 and DP3 are wild-type strains; DP55 is a pho1Δ strain, and TH4 is a constitutive mutant. Dark color indicates phosphatase activity. (B) Photograph of a phosphatase plate assay demonstrating the range of phenotypes observed on a sample 384 plate. Coordinate I8 corresponds to the pho1Δ strain in the library. Coordinates A17 and O3 correspond to the wild type and A20 and O5 to the pho1Δ strain we included as controls. The strain at E3 is the pho7Δ strain. (C) Enlarged pictures of mutants. Mutants are shown in the bottom left corner of each tile. Both ado1Δ and aps1Δ mutants are darker in color than surrounding colonies on high-phosphate media, indicating that they are constitutive mutants, and snf5Δ and pho7Δ are lighter than the surrounding strains grown on no-phosphate media, indicating that they are uninducible mutants.