Relating growth dynamics and glucoamylase excretion of individual Saccharomyces cerevisiae cells

We have developed a novel flow cytometric procedure that allows determinati ons of properties of protein excretion in the growth medium on a cell-by-ce ll basis in Saccharomyces cerevisiae. The procedure is based on labelling o f a periplasmically secreted protein with antibodies conjugated to a fluore scent marker such as fluorescein isothiocyanate (FITC). The staining condit ions did not perturb cell growth after resuspension of stained cells in gro wth medium. Decrease in fluorescence was found to correlate with excretion of glucoamylase into the growth medium. The analysis of the staining patter n over time provides information on the behaviour of individual cells belon ging to different cell-cycle phases and can be used to calculate the specif ic excretion rate of the overall population. (C) 2000 Elsevier Science B.V. All rights reserved.