FIG 2.

Modulation of the K⁺-sensitive growth of the ΔptsN mutant by alterations in external pH and its alleviation by elevated [K⁺]_e. Shown are the growth rates (μ) of JD624 (open circles) and its ΔptsN::Kan derivative, JD660 (solid circles), with respect to [K⁺]_e. The K⁺ transporters present in JD624 and JD660 are indicated. Growth rates were determined for JD624 and JD660 following their growth in K₁, K₂₀, K₄₀, and K₁₁₅ media whose pH was maintained at 6.0 (A) and 7.8 (B). (C) Growth rates of JD624 (open circles) and JD660 (solid circles) with respect to [K⁺]_e in K₁₁₅ medium and in K₁₁₅ medium containing 100, 200, and 400 mM KCl. All growth media in panel C also contained 1 mM betaine, and their pH was 7.2.