Morphokinetic Reaction of Streptococcus faecalis (ATCC 9790) Cells to the Specific Inhibition of Macromolecular Synthesis: Nucleoid Condensation on the Inhibition of Protein Synthesis

Abstract

In glutaraldehyde-prefixed exponential-phase cells of Streptococcus faecalis the nucleoid is “frozen” in a dispersed configuration. Exposure of exponential-phase cells to threonine starvation or to antibiotics inhibiting protein synthesis resulted in progressive condensation of nucleoid fibrils producing an expanding central nucleoid zone or pool. The condensation of the nucleoid was observed to occur at a rate directly proportional to the rate of inhibition of protein synthesis. However, the extent of nucleoid condensation depended on continuing deoxyribonucleic acid synthesis. Significantly less nucleoid condensation occurred when cells were inhibited in deoxyribonucleic acid and protein synthesis than when cells were inhibited in protein synthesis alone. These results suggest a model in which, during nucleoid replication, the chromosome fibrils are normally maintained in a dispersed state by the active agents of transcription-translation, such as ribonucleic acid polymerase molecules and ribosomes.