The wild-type Bacillus subtilis strain used was DP-B1066 [30] . It contains a vector-only insertion with no hemolysin. DP-B980 and DP-B1512 contain single copies of hly and pfo from L. monocytogenes and Clostridium perfringens, respectively, under the isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible promoter p spac from plasmid pAG58-ble-1 [29] . B. subtilis were grown on brain-heart infusion (BHI) agar without antibiotics at room temperature. Transformed mouse embryonic fibroblasts (MEFs) were a kind gift from N. Mizushima [36] . The cells were grown in Dulbecco's Modified Eagle Medium (DMEM) and 10% fetal bovine serum (FBS) and passaged a maximum of 5 times when the cells reached approximately 80% confluency. MEFs with a passage of greater than 5 were not used for experimentation.