FIG. 4.

Expression of D1-H2 annuls the acetyl-phosphate-dependent phosphorylation of ArcA in vivo. The λΦ(lldP′-lacZ) and the λΦ(cydA′-lacZ) reporter strains ECL5002 and ECL5003 and their ΔarcB isogenic strains ECL5012 and ECL5004 transformed with either the wild-type or mutant D1-H2-expressing plasmid were grown aerobically in defined medium [1 mM KH₂PO₄, 40 mM KCl, 34 mM NaCl, 20 mM (NH₄)₂SO₄, 1 μM FeSO₄, 0.3 mM MgSO₄, 1 μM ZnCl₂, 10 μM CaCl₂, and 0.1 M MOPS, at a final pH of 7.6] supplemented with 20 mM pyruvate and 1.3 mM arabinose. For the growth of λΦ(lldP′-lacZ)-bearing strains, the above medium was supplemented with 20 mM l-lactate. At an OD₆₀₀ of 0.4, the cultures were harvested and the β-galactosidase activity was assayed. The data are the average of four experiments, and the standard deviation values are indicated. Empty bars, ECL5002 and ECL5003, carrying the wild-type ArcB; solid bars, untransformed ECL5004 (ΔarcB) and ECL5012 (ΔarcB); hatched bars, ECL5004 and ECL5012 transformed with plasmids pBAD30, pMX020 (D1-H2), pMX021 (D1*-H2), pMX022 (D1-H2*), or pMX023 (D1*-H2*).