Sugar system promoters show a linear increase with CRP-reporter activity but with different slopes that match the hierarchy. Promoter activity at mid exponential phase of each sugar system promoter in the presence of its cognate sugar and one of the five other sugars, normalized to when only its cognate sugar is present, as a function of the promoter activity of a CRP reporter normalized to its highest value. Each color represents a different sugar system promoter (lacZ light blue, araB blue, xylA brown, rhaB orange, srlA yellow, rbsD green). Inset: promoter activity at mid-exponential phase in a two sugar mixture in the presence of external cAMP at 0,0.15,0.3,0.6,1.25,2.5,5 mM. The promoters are lacZ and rbsD measured with external cAMP in lactose + ribose; araB and rhaB measured with external cAMP in arabinose + rhamnose.