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Fig. 7 | Microbial Cell Factories

Fig. 7

From: EctD-mediated biotransformation of the chemical chaperone ectoine into hydroxyectoine and its mechanosensitive channel-independent excretion

Fig. 7

Inhibtion of the uptake of [1-14C]glycine betaine via the ProU and ProP transporters by an excess of ectoine and 5-hydroxyectoine. The E. coli mutant strains BK32 (ProP ProU+) (a, b) and MKH17 (ProP+ ProU) (c, d) were cultivated in MMA with 0.4 M NaCl at 37 °C to early exponential phase (OD578 0.3). Two millilitre aliquots were taken and mixed with a solution containing non-labeled glycine betaine and [1-14C]glycine betaine (the final concentration of glycine betaine in the uptake assay was 100 µM), and the uptake of [1-14C]glycine betaine by the cells was measured over time (for 5 min). Import of glycine betaine is shown in red. In parallel assays, the inhibition of [1-14C]glycine betaine uptake was measured with an excesses of either ectoine (a, c) or 5-hydroxyectoine (b, d). For strain BK32 (ProP ProU+), ectoine or 5-hydroxyectoine was provided in 100-, 500-, and 1000-fold excess; for strain MKH17 (ProP+ ProU), ectoine or 5-hydroxyectoine was provided in 10-, 50-, and 100-fold excess. As a control, a tenfold excess of unlabeled glycine betaine was added to the [1-14C]glycine betaine mixture (grey symbols) to monitor the inhibition of [1-14C]glycine betaine import by glycine betaine itself. The values shown are the means and standard deviations of four independently tested cultures

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