On the structure of the folded chromosome of Escherichia coli

Abstract

After careful lysis of exponentially growing Escherichia coli cells, the DNA is released in a highly-folded conformation (Stonington & Pettijohn, 1971), sedimenting as an heterogeneous population of structures with sedimentation coefficients ranging from 1300 s to 2200 s. Chromosomes arrested at initiation by amino-acid starvation sediment as an homogeneous 1300 s species. The gradual bimodal decrease in sedimentation rate seen after amino-acid starvation suggests that the faster sedimenting structures in exponentially growing cells represent the folded chromosomes at more advanced stages in their replication cycle.