FIG. 1.

Effect of Na⁺ on the growth rate of C. salexigens DSM 3043 in the presence of a constant 2.0 M concentration of Cl⁻ salts. The growth rate of the strain was determined in modified M63 medium (M63-5× Mg-Fe; see text) supplemented with 10 mM glucose, the indicated concentrations of Na⁺ (supplied as NaCl), and KCl, added at concentrations such that the sum of the NaCl and KCl was constant at 2.0 M. When used, glycine betaine was added at 1 mM. Cells were first grown to saturation in liquid Luria-Bertani medium (4) with 1 M NaCl, subcultured at a 1:100 dilution into M63-5× Mg-Fe-10 mM glucose-2.0 M NaCl, and grown to saturation. The cells were subcultured at a 1:50 dilution into M63-5× Mg-Fe-10 mM glucose containing various combinations of NaCl and KCl, and the growth rates were determined from the increases in cell density, measured as light scattering at 600 nm (A₆₀₀), as a function of time. The final density in all cultures containing ≥0.23 M Na⁺ was ∼2 × 10⁹ cells/ml (A₆₀₀ = 1.2 to 1.5).