Duplication frequency in a population of Salmonella enterica rapidly approaches steady state with or without recombination

Andrew B. Reams, Eric Kofoid, Michael Savageau, John R. Roth

Research output: Contribution to journalArticle

72 Scopus citations

Abstract

Tandem duplications are among the most common mutation events. The high loss rate of duplication suggested that the frequency of duplications in a bacterial population (1/1000) might reflect a steady state dictated by relative rates of formation (kF) and loss (kL). This possibility was tested for three genetic loci. Without homologous recombination (RecA), duplication loss rate dropped essentially to zero, but formation rate decreased only slightly and a steady state was still reached rapidly. Under all conditions, steady state was reached faster than predicted by formation and loss rates alone. A major factor in determining steady state proved to be the fitness cost, which can exceed 40% for some genomic regions. Depending on the region tested, duplications reached 40-98% of the steady-state frequency within 30 generations - approximately the growth required for a single cell to produce a saturated overnight culture or form a large colony on solid medium (10 9 cells). Long-term bacterial populations are stably polymorphic for duplications of every region of their genome. These polymorphisms contribute to rapid genetic adaptation by providing frequent preexisting mutations that are beneficial whenever imposed selection favors increases in some gene activity. While the reported results were obtained with the bacterium Salmonella enterica, the genetic implications seem likely to be of broader biological relevance.

Original languageEnglish (US)
Pages (from-to)1077-1094
Number of pages18
JournalGenetics
Volume184
Issue number4
DOIs
StatePublished - Apr 2010

ASJC Scopus subject areas

  • Genetics

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