Figure 4.

Relative fitness of the rpoB mutants measured at 42.2°C in DM25 in different genetic backgrounds. The mean relative fitness values, calculated from 6 replicates, are indicated on top of the bars. The gray color corresponds to an advantageous fitness effect of the mutations in relation to the ancestor and the dark color corresponds to a deleterious fitness effect of the mutations in relation to the ancestor. The asterisks represent significant deviation from the null hypothesis that mean fitness equals 1.0, with one and three asterisks denoting significance at P < 0.05 and P < 0.001, respectively.