Essential Genes Are More Evolutionarily Conserved Than Are Nonessential Genes in Bacteria

  1. I. King Jordan,
  2. Igor B. Rogozin,
  3. Yuri I. Wolf, and
  4. Eugene V. Koonin1
  1. National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, USA

Abstract

The “knockout-rate” prediction holds that essential genes should be more evolutionarily conserved than are nonessential genes. This is because negative (purifying) selection acting on essential genes is expected to be more stringent than that for nonessential genes, which are more functionally dispensable and/or redundant. However, a recent survey of evolutionary distances between Saccharomyces cerevisiae and Caenorhabditis elegans proteins did not reveal any difference between the rates of evolution for essential and nonessential genes. An analysis of mouse and rat orthologous genes also found that essential and nonessential genes evolved at similar rates when genes thought to evolve under directional selection were excluded from the analysis. In the present study, we combine genomic sequence data with experimental knockout data to compare the rates of evolution and the levels of selection for essential versus nonessential bacterial genes. In contrast to the results obtained for eukaryotic genes, essential bacterial genes appear to be more conserved than are nonessential genes over both relatively short (microevolutionary) and longer (macroevolutionary) time scales.

Footnotes

  • 1 Corresponding author.

  • E-MAIL koonin{at}ncbi.nlm.nih.gov; FAX (301) 435-7794.

  • Article and publication are at http://www.genome.org/cgi/doi/10.1101/gr.87702. Article published online before print in May 2002.

    • Received January 23, 2002.
    • Accepted March 25, 2002.
| Table of Contents

Preprint Server