✋ How E. coli can divide every 20 minutes when it takes about 38 minutes to complete a DNA replication cycle
When cells divide rapidly, a new cycle of replication begins before the current cycle of replication is complete. At any given time, there can be six or eight replication forks synthesizing DNA simultaneously inside the cell.
In order for the cell to divide every 20 minutes, it suffices for one replication cycle to complete every 20 minutes. This means that the origins are triggered every 20 minutes. When the daughter chromosome separates into daughter cells, they are already partially replicated in preparation for the next cell division.
Cell division in E. coli