This project investigates how metabolic energy is coupled to betaine transport in Lactobacillus acidophilus, i.e., whether it is ATP-driven or chemiosmotically coupled to the flux of H+ or other ions. A second objective is to investigate the mechanism by which osmotic upshock activates the transport carrier. The effects of varying the driving forces for transport and the osmotic pressure on betaine uptake will be studied, employing primarily intact cells and membrane vesicles. The third objective is to clone the betaine permease gene of Lactobacillus into Escherichia coli to study energy coupling mechanisms and regulation in a system that is better understood with respect to bioenergetics. The permease gene will be cloned into Gram positive bacteria of industrial and agricultural importance, such as Streptococcus and Clostridium. %%% Many species of bacteria tolerate high salinity by accumulating high levels of low-molecular weight chemicals. One stain has been isolated that is significantly more resistant to osmotic stress than other strains because it possesses an active glycine betaine (betaine)-specific active transport system. This betaine permease is unique in that it is activated, and not induced, by increased osmotic pressure, and thus offers a new opportunity for studying regulation of solute transport.
