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Figure 2 | BMC Microbiology

Figure 2

From: Multidrug resistance protein MdtM adds to the repertoire of antiporters involved in alkaline pH homeostasis in Escherichia coli

Figure 2

E. coli Δ mdtM cells complemented with wild-type mdtM can grow at alkaline pH. (A) Growth phenotypes of ΔmdtM E. coli BW25113 cells transformed with a multicopy plasmid encoding wild-type MdtM (pMdtM) or the dysfunctional MdtM D22A mutant (pD22A) at different alkaline pH’s on LB agar. As indicated, 4 μl aliquots of a logarithmic dilution series of cells were spotted onto the solid media and the plates were incubated for 24 h at 37°C prior to digital imaging. (B) Growth of ΔmdtM E. coli BW25113 cells complemented with pMdtM or the pD22A mutant in liquid LB media at different alkaline pH values. Data points and error bars represent the mean ± SE of three independent measurements. (C) Comparison of expression levels of recombinant wild-type and D22A mutant MdtM at three different pH values by Western blot analysis of DDM detergent-solubilised membranes of E. coli BW25113 cells that overproduced the protein from plasmidic DNA. Cells harbouring empty pBAD vector were used as a negative control. Each lane contained 10 μg of membrane protein.

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