IMPORTANCE OF THE REPLICATION ORIGIN SEQUESTRATION IN CELL-DIVISION OF ESCHERICHIA-COLI

The DNA adenine methyltransferase of Escherichia coli methylates adeni nes at GATC sequences. The mutant deficient in this methylase has no a pparent deficiency in the cell division process in spite of the absenc e of both synchrony in initiations of chromosomal DNA replication and sequestration of replication origin (oriC) at hemimethylated state. Ho wever, the dam mutant cannot resume cell division after hyperosmotic s hock differing from the wild-type strain. This inhibition is not provo ked by induction of the cell division inhibitor, SfiA protein. Althoug h the FtsZ protein is present in the dam mutant in a reduced amount co mpared to wild-type, the quantitative difference of this protein is no t the main reason of division arrest provoked by hyperosmotic shock. T his observation supports the Idea of oriC-membrane interaction playing a role both in chromosome partitioning and cell division as predicted by replicon theory.