Lactate efflux-induced electrical potential in membrane vesicles of Streptococcus cremoris.

Publisher Website
Google Scholar
Abstract
A procedure was developed for isolating membrane vesicles from the homolactic fermentative bacterium S. cremoris. The membrane vesicles had a right-side-out orientation as shown by freeze-etch EM and were free of cytoplasmic constituents. The membrane vesicles retained their functional properties and accumulated the amino acids L-leucine, L-histidine and L-alanine in response to a valinomycin-induced K diffusion gradient. Studies with these membrane vesicles strongly supported the possibility that there was a proton motive force-generating mechanism by end product efflux. Lactate efflux from membrane vesicles which were loaded with L-lactate and diluted in a lactate-free medium led to the generation of an electrical potential across the membrane. Lactate efflux is apparently an electrogenic process by which L-lactate is translocated with more than 1 proton.