Fig. 1.

E. coli tsf mutants are resistant to CdiA-CT^EC869. (A) E. coli MG1655 target strains carrying the indicated tsf alleles were cocultured with E. coli EPI100 inhibitor cells that deploy CdiA-CT^EC869 (EC869), CdiA-CT_o11^EC869 (o11), CdiA-CT^ECL (ECL), CdiA-CT^EC536 (536), or CdiA-CT^EC93 (EC93) toxins. After 3 h, viable cell counts for each population were determined and used to calculate the competitive index as described in Materials and Methods. Mock inhibitors do not express a CDI system. Data are presented as averages ± SEM for three independent experiments. (B) E. coli EPI100 inhibitor cells expressing CdiA-CT^EC869 were cultured at a 1:1 ratio with E. coli MG1655 target strains carrying the indicated tsf alleles. Total RNA was isolated after 10 and 20 min and subjected to Northern blot hybridization for tRNA_CUG^Gln. Because CDI^EC869 inhibitor cells are immune to toxin activity, 50% substrate conversion is indicative of complete cleavage in target cells. (C) Structure of the E. coli EF-Tu·EF-Ts complex [Protein Data Bank (PDB) ID code 1EFU]. The locations of EF-Ts Ala202, Arg219, and the coiled-coil domain are indicated.