FIG. 1.

Effect of peptone on the growth and the intracellular amino acid pools of E. coli NCIMB 10214 at high osmolarity. (a) Comparison of the growth stimulation by peptone and glycine betaine in the following: 0.5 M NaCl (○); 0.5 M NaCl plus 0.5% (wt/vol) peptone (▴); 0.5 M NaCl plus 1 mM glycine betaine (●); and 0.5 M NaCl plus 0.5% (wt/vol) peptone plus 1 mM glycine betaine (■). Cells were grown to exponential phase in McIlvaine’s medium exactly as described in Materials and Methods. Samples for amino acid analysis of high osmolarity cultures in the presence (A) and absence (A′) of peptone were taken in mid-log phase of growth. In addition, samples for amino acid analysis in the presence of peptone were taken at points B and C. (b) Main intracellular pools of amino acids at high osmolarity in the absence and presence of peptone (0.5%, wt/vol). Samples were taken at points indicated in panel a, and the intracellular pools of amino acids were determined exactly as described in Materials and Methods. Levels for pools of free glutamate (E), glutamine (Q), and proline (P) are indicated.