FIG. 4.

Expression of ehuB in S. meliloti. (A) Induction of ehuB by ectoines. Cells of strain R4-39 were grown in LAS medium to mid-exponential phase and then divided into four portions. Samples were taken at various time intervals and assayed for UidA (or β-glucuronidase [GUS]) activity. One culture was untreated (◊), 1 mM ectoine was added to the second culture (⧫), 1 mM hydroxyectoine was added to the third culture (▵), and 1 mM glycine betaine was added to the fourth culture (▴). (B) Influence of ectoine concentration and medium salinity on the induction of ehuB by ectoine. Cells were grown to mid-exponential phase in LAS medium without (◊) or with (⧫) 0.5 M NaCl, with different external ectoine concentrations, and then were assayed for UidA activity.