FIG 8.

Influence of the ProP and ProU ectoine uptake systems on the extracellular amounts of ectoine and hydroxyectoine. E. coli strains FF4169, LC6, LC7, and SK51 carrying plasmid pASTI1 (Mut 12; point mutation in the −35 region) (Fig. 3A) were cultivated in MMA containing either 0 M NaCl (A) or 0.4 M NaCl (B) for 48 h, and the extracellular ectoine/hydroxyectoine content was 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. The relevant genotypes of the E. coli strains used are as follows: FF4169, otsA1::Tn10 proP⁺ proU⁺; LC6, otsA1::Tn10 proP proU⁺; LC7, otsA1::Tn10 proP⁺ proU; and SK51, otsA1::Tn10 proP proU.