Cell-cycle-specific inhibition by chloramphenicol of septum fromation and cell division in synchronized cells of Bacillus subtilis

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Abstract
The relationship between protein synthesis and processes of cell division was studied by using synchronized cells of B. subtilis 168. The addition of chloramphenicol at the beginning of synchronous growth prevented septum formation and cell division, suggesting the requirement of protein synthesis for the processes of cell division. Experiments in which the drug was added to the cells at different cell ages showed that the protein synthesis required for the initiation of septum formation was completed at about 15 min and that the protein synthesis required for cell division was completed at about 45 min. By interpreting the result from the concept of the transition point for protein synthesis, it was suggested that the processes of cell division in B. subtilis require at least 2 kinds of protein molecules which are synthesized at distinct stages in the cell cycle. This was supported by the result of an experiment in which starvation and the readdition of a required amino acid to exponentially growing cells induced 2 steps of synchronous cell division. Further, the 2 transition points are in agreement with the estimations obtained by residual division after the inhibition of protein synthesis in asynchronous cells. The relationship of the timing between the completion of chromosome replication and the 2 transition points was also studied.