Fluorescein diacetate hydrolysis as an estimator of microbial biomass on coniferous needle surfaces

Estimating microbial standing crops and microbial production in naturalhabitats has been difficult for microbial ecologists. The present paper describes asimple spectrophotometric assay based on the hydrolysis of fluorescein diacetatewhich estimates well the standing crops of microbial cells on coniferous needles andtwigs. A technique is also presented for correlating optical density readings withactual dry weights of microbial cells epiphytic on needles, and thus forstandardizing the assay. The assay shows promise of broad applicability to othermicrobial habitats.