E. coli Chromosome Structure Research

Our major research interests concern the biology of chromosomes. Because chromosomes are the rarest yet one of the most important components of the cell, the cell devotes considerable resources to their care and feeding. E. coli, when doubling every hour or more, contains a single circular chromosome. It is replicated once per cell cycle from one, bi-directional origin of replication. The chromosome is 1.5 mm in length (4.7 million bp) and is compacted to fit into a space that can be best represented by a 0.5 um x 0.5 um cylinder. The chromosome contains large (50-100 kb) loops of DNA that are independently supercoiled. This structure reduces the size of the chromosome to ~900 nm. To fit in its alloted space, the chromosome must be compacted and additional 2 to 3 fold. Compaction is carried out by several mechanisms: small DNA binding and bending proteins, HU, HNS, IHF, FIS and Csp’s; a large coiled-coil SMC protein, MukB; topoisomerases, and mRNA. Our lab studies the role that the essential Csp proteins play in chromosome biology.