Figure 4.

Growth properties of tRNA^Ala knockout cells expressing tRNA^Ala with G⋅U or the indicated substitution. Knockout cells do not grow on minimal medium unless active tRNA^Ala is produced from a plasmid. Agar plates containing (A) glucose minimal medium or (B) LB rich medium were spotted with serial dilutions of cultures expressing the indicated tRNA^Ala. As the growth patches in A developed, cells expressing G⋅U tRNA grew better than those with C-C tRNA, but this difference is more subtle after 44 hr (shown above) when growth also becomes apparent for cells expressing G-A and C-A tRNAs. The sector in A corresponding to the plasmid without a tRNA gene insert shows the dilution key. The speckles in B are occluded air bubbles.