Quantitative and physiological analyses of chloride dependence of growth of halobacillus halophilus

A quantitative analysis of the Cl- dependence of growth of Halobacillus halophilus was performed. Optimal growth rates were obtained at Cl- concentrations of between 0.5 and 2.0 M, and the final yield was also strictly dependent on the Cl- concentration. Br- but not I-, SO42-, NO2-, SO2-, OCN-, SCN-, BO2-, or BrO3- could substitute for Cl-. To analyze the function of chloride, chloride concentration was determined. At low external Cl- (Cle-) concentrations, the growth rate was low and Cl- was excluded from the cytoplasm; increasing the Cle- concentration led to an increase in the growth rate and an energy-dependent uptake of Cl-, thus decreasing the Cle-/internal Cli- gradient from >/=10 at 0.1 M Cle- to a nearly constant value of 2 at Cle- concentrations which allowed optimal growth. Two membrane proteins with apparent molecular masses of 31 and 16 kDa which were identified to be specific for Cl--grown cultures are possible candidates for a chloride uptake system.