FIG 2.

Relative fitness as a function of chromosomal location of the tufB operon in strains with a tufA gene present (triangle) or deleted (square). All values are relative to the respective isogenic strain with the tufB operon at its native location (circle). The red area indicates the effect of gene dosage on bacterial fitness, and the green area indicates the regulatory buffer of the tufB gene by which upregulation of gene expression decreases the effect of reduced gene dosage. The gray cones show the mutational buffer by which genetic alteration can upregulate gene expression and, thereby, decrease the effect of reduced gene dosage.