Alterations in the Morphology of Bacillus subtilis After Exposure to β-Lysin and Ultraviolet Light

Viable counts, turbidities, and electron micrographs of Bacillus subtilis exposed to beta-lysin and ultraviolet light (UV), singly or in combination, were compared in an attempt to relate death with changes in morphology. The decreases in survival of both the beta-lysin- and UV-treated cells were rapid and preceded decreases in turbidity, as well as the changes in morphology. No significant differences were observed in turbidity reduction or morphological alterations of control cells from those of cells exposed to UV light. These cells developed prominent subcell wall spaces during incubation in the hypertonic stabilizing medium. No observable damage in either the cell wall or the cell membrane had taken place during 4 hr, but by 20 hr extensive damage of these two structures was apparent. The control and UV-treated cells exposed to beta-lysin did not develop prominent subcell wall spaces. Within 2 hr, lesions were observable in their cell walls, and the cytoplasmic membranes were permeable to phosphotungstic acid. The damage to these structures became more extensive with time. Although the visible changes of control and UV-treated cells were evident much later than those induced by beta-lysin, the morphological alterations in all cells were similar. It appeared that beta-lysin caused an accelerated release of an autolytic enzyme which digested the cell walls.