FIG. 5.

Expression of the yklA-lacZ (A) and ykzA-lacZ (B) transcriptional fusions during the growth cycle in minimal medium or nutrient broth and after exposure to salt stress. Cells were grown as described in Materials and Methods, and samples were taken every 30 or 60 min as indicated. (A) solid symbols indicate growth of B. subtilis BFS1816, and open symbols indicate β-galactosidase activity. Circles, nutrient medium; squares, minimal medium. (B) Solid squares represent growth of B. subtilis BFS1818 in minimal medium, and open squares indicate β-galactosidase activity. The influence of the addition of salt during exponential growth on the accumulation of β-galactosidase is also indicated (open triangles). The point of salt addition is indicated by an arrow. OD550, optical density at 550 nm.