Fig. 4.

EmrE-W63G is capable of supporting growth of BW25113 ΔpuuP when putrescine is the sole nitrogen source. (A) BW25113 ΔpuuP E. coli cells transformed with pSN1, pSN1-EmrE, pSN1-EmrE W63G, or pSN1-EmrE W63G I68N Q81L (triple) were streaked onto minimal medium plates containing W-salts, glucose (as the carbon source), and (NH₄)₂SO₄ (W + Glu + AS) or putrescine (W + Glu + Put) as the sole nitrogen source. Growth was analyzed after a 48-h incubation at 37 °C. (B) Growth was conducted in minimal media with putrescine as the sole nitrogen source, and OD₆₀₀ readings were taken every hour for 30 h. Triangles: EmrE W63G; circles: EmrE; squares: pSN1 (vector).