Growth rate toxicity phenotypes and homeostatic supercoil control differentiate Escherichia coli from Salmonella enterica serovar typhimurium

Academic Article


  • Escherichia coli and Salmonella enterica serovar Typhimurium share high degrees of DNA and amino acid identity for 65% of the homologous genes shared by the two genomes. Yet, there are different phenotypes for null mutants in several genes that contribute to DNA condensation and nucleoid formation. The mutant R436-S form of the GyrB protein has a temperature-sensitive phenotype in Salmonella, showing disruption of supercoiling near the terminus and replicon failure at 42°C. But this mutation in E. coli is lethal at the permissive temperature. A unifying hypothesis for why the same mutation in highly conserved homologous genes of different species leads to different physiologies focuses on homeotic supercoil control. During rapid growth in mid-log phase, E. coli generates 15% more negative supercoils in pBR322 DNA than Salmonella. Differences in compaction and torsional strain on chromosomal DNA explain a complex set of single-gene phenotypes and provide insight into how supercoiling may modulate epigenetic effects on chromosome structure and function and on prophage behavior in vivo. Copyright © 2007, American Society for Microbiology. All Rights Reserved.
  • Authors

    Published In

    Digital Object Identifier (doi)

    Author List

  • Champion K; Higgins NP
  • Start Page

  • 5839
  • End Page

  • 5849
  • Volume

  • 189
  • Issue

  • 16