Figure 5. Effect of reduced translation rate on cellular fitness and gene expression.

The canonical GFP-L gene, which possesses a consistently low G + C content over the entire gene sequence, was cloned and expressed in plasmid vectors with either a weak (pFAB3845) or strong (pFAB3857) promoter. Cloned constructs were assayed in the wild-type E. coli (WT, strain BW25113) and in a streptomycin resistant derivative (Sm^R) whose global translation rate was reduced by introducing the P90Q mutation into the rpsL gene. (A) Comparison of relative growth rates of the WT and Sm^R strains expressing the canonical GFP-L gene from strong and weak promoters. Relative growth rates calculated as the average growth rate of GFP-expressing strain divided by the average growth rate of a no-expression control. (B) Comparison of gene expression levels in the WT and Sm^R strains expressing the canonical GFP-L gene from weak and strong promoters. Gene expression levels determined by measuring cellular fluorescence intensity. Results represent mean ± standard deviation of three biological replicates.