FIG. 1.
Growth of saprophytic mutant B. bacteriovorus strain M11/Strep on heat-killed E. coli K-12. M11/Strep was cultured on double-layer agar plates containing autoclaved E. coli K-12 within the top layer. Different dilutions of M11/Strep from 10−5 to 10−7 were plated. The facultative predacious strain formed visible colonies which were surrounded by a zone of lysis in the lawn of dead prey cells. In the 10−5 dilution all remains of the heat-killed bacteria were lysed, while in the higher dilutions the remaining dead bacteria were visible as opaque areas.