Figure 1.

The bgl promoter (Pbgl) activities in the wild type and various isogenic genetic backgrounds. Cells were grown in M63 minimal media with shaking at 37 °C. At least four samples were collected at OD₆₀₀ values of 0.2 to 1.0 during the exponential growth phase. Bacterial samples were subject to β-galactosidase assays as described in Section 4, and the enzyme activities were calculated using the equation [(OD₄₂₀−1.75 × OD₅₅₀)/(sample volume in mL × time in min)] × 1000. For a given test strain, the slope of OD₆₀₀ values versus β-galactosidase activities was referred to as the promoter activity. (A) Diagram showing the lacZ transcriptional reporter for the bgl promoter (Pbgl-lacZ). Pbgl (−205 to + 54 relative to the transcriptional start site) with no terminators was fused to the upstream region of the lacZ’s RBS (that is, to TTTCACACAGGAAACAGCT) at the lac locus, replacing lacI and the lacI/lacZ intergenic region. The native bgl operon remained intact. However, for strain Bgl⁺, there is an IS5 element oriented in the inverse direction and inserted at −207.5 upstream of the bglG translation start site. For both the promoter reporter and the native bgl operon, the blue bars represent the Crp binding sites (O_Crp) while the red bars represent the proposed H-NS binding sites (O_HNS). (B) Pbgl activities in cells grown with glycerol as the primary carbon source. (C) Pbgl activities in cells grown with glycerol and salicin as carbon sources.