Figure 2From: Positive selection at high temperature reduces gene transcription in the bacteriophage ϕX174Transcript levels differ between ancestor and promoter mutant strains at two temperatures in three bacterial hosts. The amount of transcript starting from the D promoter was measured relative to the amount of transcript starting from the B promoter for each phage strain using quantitative PCR. Injection of DNA into host was synchronized by attachment at 15°C and then addition to LB at 37°C. Samples were taken at 4 and 8 min after injection, which is prior to the start of cell lysis. The y-axis indicates the ratio of the D transcript to the B transcript. Bars are the mean and error bars the standard error of two (S. sonnei) or three replicate assays. Solid bars are mutant strains with non-synonymous substitutions in C, hatched bars are synonymous in C. Relative transcript level of the ancestor is significantly greater than the four mutants for all host/temperature/time combinations (Table 2). Note the difference in scale for the S. sonnei graph.Back to article page