FIG. 3.

Expression of D1-H2 abrogates the ArcA-P transcriptional regulation under stimulating conditions. The λΦ(lldP′-lacZ) and the λΦ(cydA′-lacZ) reporter strains ECL5002 and ECL5003 were transformed with either the wild-type or mutant D1-H2-expressing plasmid. The λΦ(cydA′-lacZ)-bearing strains were cultured anaerobically in buffered LB containing 0.1 M MOPS (pH 7.4), 20 mM d-xylose, 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 and expressed in Miller units. The data are the average of four experiments, and the standard deviation values are indicated. Solid bars, untransformed strains; hatched bars, strains transformed with plasmids pBAD30, pMX020 (D1-H2), pMX021 (D1*-H2), pMX022 (D1-H2*), or pMX023 (D1*-H2*).