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 300mM). The same tendency was observed when NaCl was replaced with KCl, although the Na
+ ion was very low (about 15mM). On the contrary, intracellular concentrations of Mg
2+ and Ca
2+ 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 100mM, 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 200mM) 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.
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