[Effect of hydrogen ions on the morphology and ultrastructure of Bacillus megaterium].

The morphology and ultrastructure of the cells of Bacillus megaterium depend on the concentration of hydrogen ions in the medium which affect, first of all, the function of division. The changes induced by hydrogen ions are temporary and disappear when the cells are put under normal conditions of growth. The "acid-resistant" strain of Bac. megaterium remains viable at a very high concentration of hydrogen ions (pH=4.2) and, though its morphology changes drastically, no essential damages are found, i.e. the cells become adapted to new conditions. The changes are reversible.