A yeast lysis assay in the microtiter plate format improved precision and t
hroughput and led to an improved algorithm for estimating lag time. The ass
ay reproducibly revealed differences of 10% or greater in the maximal lysis
rate and 50% or greater in the lag time. Clonal differences were determine
d to be the major source of variation. Microtiter-based assays should be us
eful for screening for drug susceptibility and for analyzing mutant phenoty
pes.