Abstract
A method is presented to identify esterase-synthesizing microbial colonies within mixed culture plates by utilizing induced esterase hydrolysis of nonfluorescent butyryl ester of 7-hydroxy-4-methylcoumarin to the highly fluorescent 7-hydroxy-4 methyl umbelliferone. Microscopy procedures for making esterase loci of fungal mycelia visible with this reaction are described.