Figure 2.

The pedigree of rrn-deletion strains. Inactivated rRNA operons are indicated by capital letters derived from their specific operon names (for example, A for rrnA). When the inactivation was carried out by a deletion/insertion mutation, a capital letter is followed by a lowercase letter c or z representing the inserted gene cat⁺ or lacZ⁺, respectively (for example, Ac for rrnA∷cat⁺). pTRNA, pHK-rrnC⁺, and pSTL102 contain Spc, Km, and Ap resistance markers, respectively. All rRNA operons cloned in the plasmids shown contain the gene for tRNA Glu-2.