(A) Protection against the antimicrobial action of propionicin F conferred by the pcfI gene. The results represent the averages of the results of three independent experiments, and standard deviations are indicated. (B) Food-grade expression of propionicin T1 from IFO12426 (pSL106) compared to that of wild-type producer strain P. thoenii 419. A, IFO12426; B, P. thoenii419; C, IFO12426 (pTD104); D, IFO12426 (pSL106); E, IFO12426 (pSL104).