TABLE 2.
Stress-protective properties of compatible solutes in B. subtilis
| Compatible solute | Uptake via: |
Stress protectiona |
||||||
|---|---|---|---|---|---|---|---|---|
| OpuA | OpuB | OpuC | OpuD | OpuE | Osmostress (1.2 M NaCl) | Heat stress (52°C) | Cold stress (15°C) | |
| Glycine betaine | + | − | + | + | − | + | + | + |
| Choline | − | + | + | − | − | + | + | + |
| Homobetaine | + | − | + | − | − | + | + | + |
| Carnitine | − | − | + | − | − | + | + | + |
| γ-Butyrobetaine | − | − | + | − | − | + | + | + |
| Crotonobetaine | − | − | + | − | − | + | + | + |
| DMSA | + | − | + | + | − | + | + | + |
| Proline | − | − | − | − | + | + | + | − |
| Proline betaine | + | − | + | − | − | + | − | + |
| Choline-O-sulfate | − | − | + | − | − | + | − | − |
| Ectoine | − | − | + | − | − | + | − | − |
| Glutamateb | − | − | − | − | − | + | + | − |
The osmotic stress protection of the various compatible solutes was tested for B. subtilis cells that were grown in SMM with 1.2 M NaCl; heat stress protection was evaluated for cells grown in SMM at 52°C, and chill stress protection was assessed for cells grown in SMM at 15°C. The concentration of the compatible solutes in the growth assays was 1 mM each. The data on the protection of B. subtilis from osmotic and heat stress by compatible solutes were compiled from previously reported data (10, 36). The listed data for protection of B. subtilis from cold stress by compatible solutes are from this study.
Glutamate is taken up under the various stress conditions via the GltT transporter (M. Bleisteiner and E. Bremer, unpublished data).