Fig 2.

Expression of MazF-cd inhibits growth and MazE-cd prevents toxicity. (A) Growth curve of E. coli BW25113 cells harboring the pBAD33-mazF-cd or pBAD33-mazF-ec plasmid either induced (with arabinose) or uninduced (without arabinose). Optical density was monitored beginning at time zero, the point of induction. One representative experiment (of three replicates) is shown. (B) pBAD33-mazF-cd and pINIII-mazE-cd constructs were cotransformed into BW25113 cells and streaked onto M9 minimal medium plates containing either 0.015% arabinose (+MazF) or 0.015% arabinose plus 1 mM IPTG (+MazF +MazE). The coinduction of both toxin and antitoxin permits normal growth in these cells (left); however, toxin-only expression prevents cell growth (right). The center diagram identifies the strains in each sector of the left and right plates. Five of the six sectors are individual transformants of the BW25113 strain containing both pBAD33-mazF-cd and pINIII-mazE-cd plasmids, while the sixth was a control BW25113 strain that contained empty pBAD33 and pINIII plasmids. (C) Growth curve of C. perfringens strain 13 cells harboring pCM14-mazF-cd plasmid either induced (with lactose) or uninduced (without lactose) at time zero. Optical density was monitored immediately after the addition of lactose.