Chloride dependence of glycine betaine transport in Halobacillus halophilus

Abstract

Growth of Halobacillus halophilus is strictly chloride-dependent but the physiological basis for the chloride dependence remains to be elucidated. To address the function of Cl⁻ in H. halophilus, a physiological study was performed. It was found that uptake of the compatible solute glycine betaine under isoosmotic conditions was stimulated by increasing salt concentrations. Uptake of glycine betaine required both, Na⁺ and Cl⁻. Cl⁻ could be substituted by nitrate and bromide, but not by sulfate. Glycine betaine transport was optimal at around 0.7 M Cl⁻. Cells responded to an osmotic upshock by accumulating glycine betaine, but only in the presence of chloride. These studies revealed the first chloride-dependent glycine betaine transporter in a prokaryote.