Fig. 2. Northern blot analysis identifying tmRNAs of E.coli and N.gonorrhoeae. The probe was synthesized using ssrA^Ec as template. Strains examined were: K37, wild-type for ssrA^Ec (lane 1), K8619, isogenic with K37 except that it has the ssrA^Ec::cat allele (lane 3), and variants of K8619 carrying pGCtm (lane 2) or derivatives of pGCtm with ssrA^Ng mutant alleles (lanes 4–6).