Figure 9

Variation of lrp mRNA levels with growth phase and medium. A. Values shown are arbitrary units from standard curve-based QRT-PCR (see Methods), with bars indicating standard errors. At least four points from each of two independent experiments were used to generate each plotted value. Conditions were MOPS-glucose minimal medium, supplemented as described in Methods, in logarithmic (MinLog) or stationary phase (MinSta), or MOPS glucose defined rich medium in those growth phases (RchLog, RchSta). B-D. Direct comparison of lrp mRNA levels.B. A baseline amount of total E. coli RNA (from a mid-log phase culture in MOPS glucose plus nicotinate) was mixed with varying amounts of test RNA (all from log-phase cultures) from glucose (open circle) or rich (closed circle) cultures. The mixes were used as template for simultaneous amplification with three primer pairs. If the test cDNA preparation has the same proportion of lrp cDNA as the reference pool, the detected amount of lrp cDNA should rise with a slope of 1.0 (actual vs. detected, based on the varied amounts of test cDNA added); this is shown as a dotted line in each panel.