Quantitative and Physiological Analyses of Chloride Dependence of Growth of Halobacillus halophilus

Abstract

ABSTRACT 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 − , SO 4 2− , NO 2 − , SO 2 − , OCN − , SCN − , BO 2 − , or BrO 3 − could substitute for Cl − . To analyze the function of chloride, chloride concentration was determined. At low external Cl − (Cl e − ) concentrations, the growth rate was low and Cl − was excluded from the cytoplasm; increasing the Cl e − concentration led to an increase in the growth rate and an energy-dependent uptake of Cl − , thus decreasing the Cl e − /internal Cl i − gradient from ≥10 at 0.1 M Cl e − to a nearly constant value of 2 at Cl e − 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.