Role of galactose or glucose-1-phosphate in preventing the lysis of Streptococcus diacetilactis.

Cells of Streptococcus diacetilactis DRCI grown at 32 C in media containing glucose as the energy source were osmotically fragile and began to lyse immediately after growth was stopped (by the action of chloramphenicol or the exhaustion of glucose), unless they were then stabilized by hypertonic medium or spermine or by storage at low pH or low temperature, or both. In media containing excess glucose, with growth limited by exhaustion of some nutrient other than the energy source, the appearance of lysis was masked by the occurrence of a balance between lysis and synthesis. The osmotic fragility apparently resulted from inability of the organism to use glucose as an adequate precursor of galactosamine, and conditions of temperature and pH that promoted rapid growth on glucose were particularly conducive to the formation of cells that lysed readily. Growing the organism in media containing galactose, lactose, maltose, or glucose (at 17 C) as energy source resulted in the formation of cells that were resistant to lysis and richer in galactosamine than unstable cells formed on glucose at 32 C. The results indicate that the organism phosphorolyzes maltose to glucose plus beta-glucose-1-phosphate, and suggest that it can use the beta-glucose-1-phosphate in place of alpha-glucose-1-phosphate in the formation of cell materials.