INTERNAL CATION CONCENTRATIONS OF THE HALOTOLERANT BACTERIUM BREVIBACTERIUM SP IN RESPONSE TO THE CONCENTRATIONS AND SPECIES OF EXTERNAL SALTS

Internal cation concentrations of the halotolerant bacterium Brevibacterium sp. were investigated, with the cells grown in a complex media supplemented with nine kinds of salts. With increases in the external NaCl concentration, the amount of Na+ ion in the cells increased, while the intracellular concentration of the K+ ion remained almost constant (about 300 mM). The same tendency was observed when NaCl was replaced with KCl, although the Na+ ion was very low (about 15 mM). On the contrary, intracellular concentrations of Mg2+ and Ca2+ decreased slightly with the increase in NaCl or KCl concentrations in the medium. When the RbCl concentration in the medium was increased to more than 100 mM, Rb+ ions in the cells increased about one hundred times, 550-600 mM, while K+ ions decreased to one-tenth. The same experiment was resumed using the chemically defined medium. We observed two different phenomena. First, the intracellular Na+ content (about 200 mM) was more than ten-fold higher than that of the cells grown in the complex medium. Second, the release of K+ ions from the cells at alkaline pH was not as remarkable as that in the complex medium. The release of K+ ions observed in the complex medium was correlated with the addition of 50 mM diethanolamine-hydrochloride for adjusting medium pH at 9.0.