Fig 2.

Adjustment of the intracellular compatible-solute pool of B. subtilis to external salinity and glycine betaine availability. (A) Cultures of the wild-type strain JH642 were grown in SMM to the mid-exponential-growth phase (OD₅₇₈, about 1.5). The medium contained the NaCl concentrations indicated and 1 mM glycine betaine spiked with 0.64 μM radiolabeled [1-¹⁴C]glycine betaine. Intracellular glycine betaine (●) was quantified by scintillation counting. (B) For the analysis of cytoplasmic proline pools, cells of the B. subtilis wild-type strain JH642 were grown to the mid-exponential-growth phase (OD₅₇₈, about 1.5) in SMM with the NaCl concentrations indicated in the absence (●) or presence (○) of 1 mM glycine betaine. After extraction of the soluble solute pools from these cells, their proline content was determined by a colorimetric assay (49). (C) Cells of strain JH642 were grown to the mid-exponential-growth phase (OD₅₇₈, about 1.5) in SMM containing 1 M NaCl and the indicated concentrations of glycine betaine. Their proline content (●) was determined by a colorimetric assay (49). All data presented in this figure are the means for two independent cultures that were assayed for their internal solute concentrations in duplicate.