Secondary structure of the upper stem of 16S rRNA helix 34 of E. coli (2). Transversion G1064C and transition C1192U (E. coli numbering) in spectinomycin-resistant N. meningitidis and N. gonorrhoeae, respectively, are indicated by open letters. The locations of other spectinomycin resistance single mutations, A1191G,C and G1193A in Chlamydomonas reinhardtii (6), A1191C in N. tabacum chloroplast (17), G1193A in Nicotiana undulata chloroplast (4), and G1064U,C,A in E. coli (3), and of double mutations G1064U-C1192A, G1064C-C1192G, and G1064A-C1192U in E. coli (3) are indicated by circles.