Aldol® 495 phosphate is a chromo- and fluorigenic indicator for phosphatase activity. The colorless product is cleaved by acid and alkaline phosphatases secreted by bacteria in liquid media or on agar plates and yields an orange color. In addition, green fluorescence signals are generated if a fluorescence enhancer or a suitable matrix is present. Aldol® 495 phosphate can also be used as detecting agent for phosphatase coupled antibodies in Western blot and enzyme immune assay applications. Color and fluorescence formation is due to on an intramolecular aldolcondensation after enzymatic cleavage. The reaction proceeds equally well in the presence and absence of oxygen, i.e., in aerobic and anaerobic cultures. Well detectable color/fluorescence of bacterial colonies or liquid cultures is obtained within 16-48 h. In the presence of purified phosphatase, color and fluorescence develops within minutes to few hours.