Journal of Molecular Evolution

, Volume 41, Issue 4, pp 449–456 | Cite as

Synonymous substitution-rate constants in Escherichia coli and Salmonella typhimurium and their relationship to gene expression and selection pressure

  • Otto G. Berg
  • Mattias Martelius
Articles

Abstract

Based on the differences in synonymous codon use between E. coli and S. typhimurium, the synonymous substitution rates can be estimated. In contrast to previous studies on the substitution rates in these two organisms, we use a kinetic model that explicitly takes the selection bias into account. The selection pressure on synonymous codons for a particular amino acid can be calculated from the observed codon bias. This offers a unique opportunity to study systematically the relationship between substitution-rate constants and selection pressure. The results indicate that the codon bias in these organisms is determined by a mutation-selection balance rather than by stabilizing selection. A best fit to the data implies that the mutation rate constant increases about threefold in genes at low expression levels relative to those that are highly expressed.

Key words

Synonymous codon usage Synonymous substitution rates Genome evolution Mutation rates 

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Copyright information

© Springer-Verlag New York Inc 1995

Authors and Affiliations

  • Otto G. Berg
    • 1
  • Mattias Martelius
    • 1
  1. 1.Department of Molecular BiologyUniversity of Uppsala Biomedical CenterUppsalaSweden

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