IN-VIVO INVESTIGATIONS OF GLUCOSE-TRANSPORT IN SACCHAROMYCES-CEREVISIAE

In the present study, the glucose transport into the yeast Saccharomyc es cerevisiae has been investigated. The approach suggested is based o n a rapid sampling technique for studying the dynamic response of the yeast to rapid changes in extracellular glucose concentrations. For th is purpose a concentrated glucose solution has been injected into a co ntinuous culture at steady state growth conditions resulting in a shif t of the extracellular glucose level. Samples have been taken every 5 s for determination of extracellular glucose and intracellular glucose -6-phosphate concentrations. Attempts to fit the experimental observat ions with simulations from existing models failed. The mechanism then proposed is based on a facilitated diffusion of glucose superimposed b y an inhibition of glucose-6-phosphate. The use of the so-called in vi vo approach suggested in this article appears to be proper, because th e investigations can be performed at defined physiological states of t he microbial cultures. Furthermore, the experimental observations are not being corrupted by the preparation of the samples for the transpor t studies as it happens during radioactive measurements. (C) 1996 John Wiley & Sons, Inc.