FIG. 3.

Antilisterial substance produced by B. subtilis JH642 and 22a. (A) The strains are shown as colonies that were overlayed with soft agar containing a suspension of L. monocytogenes cells. Growth of Listeria is inhibited by wild-type (WT) JH642 and by 22a but not by the sbo and alb mutants of these organisms. Some slight inhibition is observed around the colonies of the 22a sbo and alb mutant cells. (B) A Tricine-SDS-PAGE gel that is stained with Coomassie blue shows the antilisterial peptide produced in WT JH642 but not present in cultures of strains ORB3148 (sbo) and ORB3146 (alb). (C) A bioautograph (see Materials and Methods) of the gel in panel B, showing the antilisterial activity of the peptide and the absence of activity in the lanes containing the sbo and alb mutant culture extracts.