Figure 2. Identification of cytotoxic protein from B. cereus supernatant.

A. Bacterial supernatant of B. cereus NVH 0075-95 ΔnheBC was separated on a Superdex-75 10/300 GL gel filtration column. Chromatogram of fractionated bacterial proteins is shown (fraction1–24). Protein fractions were tested on Ptk6 cells for cytotoxicity as described in Experimental procedures. Protein fractions obtained from gel filtration were analyzed by SDS-PAGE. B. Gel filtration fractions 12–14 transferred cytotoxicity to Ptk6 cells and contained two distinct proteins migrating at 34 kDa and 25 kDa (red asterisks). C. Comparing total extracellular proteins of WT and mutant B. cereus strains, two potential cytotoxic proteins (red asterisks) were absent in the supernatant of avirulent ΔplcR strain.