Ultrastructural studies on a mutant of Bacillus subtilis whose growth is inhibited due to insufficient autolysin production.

The growth of Bacillus subtilis mutant betaA177 can be inhibited under special conditions in which not enough autolytic enzymes are produced for optimal growth. Electron microscopy studies show that during growth inhibition there is localized thickening of the cell wall at positions where cells bend. A model is proposed to explain this result. Rapid growth can be restored by adding lysozyme or a B. subtilis autolysin mixture to a growth-inhibited betaA177 culture. Such addition reduces the localized wall thickening and causes other changes in surface morphology which are described and discussed. Septum formation seems to be relatively less inhibited than cell elongation when lytic enzyme levels are reduced. Measurements were made demonstrating that walls at ends of cells are morphologically different from walls at sides of cells in cultures of betaA177 growing at 51 C.