FIG 9.

Influence of an ectD deletion on ectoine/hydroxyectoine production and secretion. (A and B) E. coli strain SK51 (otsA1::Tn10 proP proU) harboring either plasmid pASTI1 (ectABCD-ask_ect) or plasmid pLC75 [ectABC(ΔectD)-ask_ect] carrying a point mutation in the −35 region of the ect promoter was grown in MMA containing 0.4 M NaCl for 24 h, and the intracellular (A) and extracellular (B) ectoine/hydroxyectoine content was then determined by HPLC analysis. (C) Comparison of the lac promoter sequence present in the cloning vector pHSG575 (89) and its mutant derivative present in plasmid pASTI14 (ectABCD-ask_ect). (D and E) Cells of strain SK51 carrying either pASTI1 or pASTI14 were grown either in MMA (D) or MMA with 0.4 M NaCl (E) for 24 h, and the extracellular ectoine and hydroxyectoine concentrations were then determined by HPLC analysis. The data shown were derived from four independently grown cultures, and each assessment of their ectoine/hydroxyectoine content was performed at least twice.