Membrane Protein Components and DNA Synthesis in Escherichia coli

Abstract

In order to correlate chromosomal replication with other aspects of bacterial cell division, Jacob, Brenner and Cuzin (1963) proposed a model (the replicon hypothesis) which suggested that these processes could be temporally coordinated if the DNA were spatially oriented via a liaison with the cell surface. According to this model, DNA synthesis would occur with the chromosome attached to the membrane, and subsequent membrane synthesis would separate the genetic replicas; the occurrence of separation between the DNA copies then leads to two daughter cells of identical genetic constitution. In its original formulation the model relies upon localized membrane growth to ensure chromosome partition, but experimental evidences have shown that most of the new membrane material is immediately randomized over the whole membrane surface, suggesting that growth follows a non-conservative, dispersive pattern, which is also in accordance with the current ideas about the “fluid” state of the membrane material (Mindich and Dales, 1972) This is not enough to disprove the replicon hypothesis since these observations necessarily concern membrane synthesis “in toto” and not the fate of any minor fraction that still might behave as predicted by the model.