Cell Cycles and Division, Bacterial

During the cell cycle, cellular components are faithfully duplicated to ensure viable new cells. Bacteria have a cell cycle quite different from eukaryotes, less so for archaea. The focus for bacteria is on Escherichia coli because it is one of the best documented organisms. In this organism, there is no classic mitosis and, by contrast, DNA segregation takes place during the replication process. Dependent on growth conditions a newborn cell may contain a replicating chromosome. This stipulates that a newborn cell is not completely new. So far, archaea have been investigated much less intensively. Nevertheless, in contrast to E. coli, DNA replication in some archaea has been observed to start at multiple origins, which resembles the eukaryotic case. Whether archaea carry out true mitosis remains to be seen. Cytokinesis in prokaryotes is carried out by a protein machine, the divisome. It is composed of some 20 different proteins, some of which are specific for cytokinesis. The composition of the divisome in Gram-negatives and Gram-positive bacteria is largely conserved. The site of division is determined at least in part by a mechanism that takes into account the position of the nucleoid as well the behavior of proteins that oscillate between the two poles.