Kinetic and Steady‐State Investigations of Solute Accumulation in Bacterial Membranes by Continuously Monitoring the Radioactivity in the Effluent of Flow‐Dialysis Experiments

Abstract

The flow-dialysis technique for studies of solute accumulation by membrane preparations was made more suitable for routine measurements by recording continuously the radioactivity in the effluent of a flow-dialysis vessel with a homogeneous flow-monitoring device for .beta.-emitters. This modification not only decreases the time and cost of a flow-dialysis experiment but also allows the direct reaction on the outcome of the experiments. Analysis of the kinetics of this automated flow-dialysis system shows that this technique can also be used for the determination of the rate of uptake of solutes into bacterial membranes. This has been confirmed in Rhodopseudomonas sphaeroides by comparing the results of Rb+ and Pi uptake studies performed by automated flow-dialysis and by the conventional filtration procedure. This application''s limitation is that solute uptake has to proceed linearly for a period of about 5 times the half-time of the response of the flow-dialysis system. The 2 described applications make automated flow-dialysis very well-suited for experiments on the bioenergetics and regulation of solute uptake into bacterial membranes. Both driving force and rate of solute uptake can now be determined in 1 experiment.