Northern analysis of relBEF transcription in response to expression of different toxins. Cultures of BW25113 contained plasmids for toxin and antitoxin expression. Toxins were induced and RNA was extracted at timepoints −1(before induction), 15, 60, and 120 min; 10-μg aliquots were subjected to electrophoresis, transferred to a membrane, and hybridized with oligoprobes relB (A), relE (B), and relF (C). Localization of the hybridization probes is shown on the map of the relBEF operon and the full-length relBEF transcript is marked by arrowhead (◄). Cultures of toxin over-expression contained the following plasmids: RelE - pVK11; MazF - pSC3326 and pSC228; MqsR - pTX3 and pAT3; YafQ - pBAD-yafQ and pUHE-dinJ; HicA - pMJ221 and pMJ331; HipA - pNK11 and pNK12. Control cultures contained the empty vectors pBAD33 and pOU82. Mupirocin (MUP) was added as a positive control for transcriptional activation of relBEF.