The consequences of genetic drift for bacterial genome complexity
Chih-Horng Kuo, Nancy A. Moran and Howard Ochman,1
-Author Affiliations
Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA
Abstract
Genetic drift, which is particularly effective within small populations, can shape the size and complexity of genomes by affecting the fixation of deleterious mutations. In Bacteria, assessing the contribution of genetic drift to genome evolution is problematic because the usual methods, based on intraspecific polymorphisms, can be thwarted by difficulties in delineating species' boundaries. The increased availability of sequenced bacterial genomes allows application of an alternative estimator of drift, the genome-wide ratio of replacement to silent substitutions in protein-coding sequences. This ratio, which reflects the action of purifying selection across the entire genome, shows a strong inverse relationship with genome size, indicating that drift promotes genome reduction in bacteria.
Footnotes
↵1 Corresponding author.
E-mail hochman@email.arizona.edu; fax (520) 621-3709.
[Supplemental material is available online at www.genome.org]
Article published online before print. Article and publication date are at http://www.genome.org/cgi/doi/10.1101/gr.091785.109.
Received January 28, 2009.
Accepted April 29, 2009.
Copyright © 2009 by Cold Spring Harbor Laboratory Press
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