SYNCHRONOUS DIVISION INDUCED IN ESCHERICHIA-COLI-K12 BY PHAGE-MU - ANALYSIS OF DNA TOPOLOGY AND GENE-EXPRESSION DURING THE CELL-CYCLE

Bacteriophage Mu mutants in gene gem (Mu gem(ts2)) induce cycles of synchronous divisions after infection of a bacterial population in steady-state conditions. In this paper, two classes of gyrB mutants, synchronizable and non-synchronizable, are described. The existence of the non-synchronizable class suggests that the gyrase B subunit is involved with Gem in the process of synchronization. Cyclical variations in DNA topology of a resident multicopy plasmid occur during synchronous growth and correlate with a modulation of the chromosomal lacZ gene expression. Transcription data for the cell division genes, ftsZ, and envA, obtained studying first steps in synchronous growth after infection, show that synthesis of the two mRNA is not constant. The specific mRNA of envA seems to be stimulated soon after infection, whereas the two transcripts initiating upstream from ftsZ apparently decrease to a basal level. In both cases, however, synthesis of the mRNA virtually doubles at the time of cell division.