FIG. 3.

Cold shock response of the ilvB mutant B. subtilis 1A228 from the BGSC. The strain was incubated as described in the legend to Fig. 1, with the addition of 20 μM (each) isoleucine and valine to overcome auxotrophy. As shown for growth at 37°C (○), this concentration allowed growth to an OD₆₀₀ of more than 1.0. Cold shock in the absence of isoleucine (●) abolished growth. The addition of 100 μM isoleucine prior to cold shock (■) permits growth to high density at 15°C, whereas the addition of 100 μM threonine (⧫) had no protective effect in this strain. Experiments with another isoleucine-auxotrophic strain, 1A57 (ilvC), revealed similar results (data not shown).