Gene-specific selective sweeps in bacteria and archaea caused by negative frequency-dependent selection

BMC Biology

Research Article

Nobuto Takeuchi¹  Kunihiko Kaneko¹  Otto X Cordero²  Eugene V Koonin³ 

[1] Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan;Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland;National Institutes of Health, National Library of Medicine, National Center for Biotechnology Information, Bethesda, USA;

关键词: Recombination Rate;    Selective Sweep;    Genomic Island;    Selection Coefficient;    High Recombination Rate;   

DOI  :  10.1186/s12915-015-0131-7

 received in 2014-10-25, accepted in 2015-03-13,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundFixation of beneficial genes in bacteria and archaea (collectively, prokaryotes) is often believed to erase pre-existing genomic diversity through the hitchhiking effect, a phenomenon known as genome-wide selective sweep. Recent studies, however, indicate that beneficial genes spread through a prokaryotic population via recombination without causing genome-wide selective sweeps. These gene-specific selective sweeps seem to be at odds with the existing estimates of recombination rates in prokaryotes, which appear far too low to explain such phenomena.ResultsWe use mathematical modeling to investigate potential solutions to this apparent paradox. Most microbes in nature evolve in heterogeneous, dynamic communities, in which ecological interactions can substantially impact evolution. Here, we focus on the effect of negative frequency-dependent selection (NFDS) such as caused by viral predation (kill-the-winner dynamics). The NFDS maintains multiple genotypes within a population, so that a gene beneficial to every individual would have to spread via recombination, hence a gene-specific selective sweep. However, gene loci affected by NFDS often are located in variable regions of microbial genomes that contain genes involved in the mobility of selfish genetic elements, such as integrases or transposases. Thus, the NFDS-affected loci are likely to experience elevated rates of recombination compared with the other loci. Consequently, these loci might be effectively unlinked from the rest of the genome, so that NFDS would be unable to prevent genome-wide selective sweeps. To address this problem, we analyzed population genetic models of selective sweeps in prokaryotes under NFDS. The results indicate that NFDS can cause gene-specific selective sweeps despite the effect of locally elevated recombination rates, provided NFDS affects more than one locus and the basal rate of recombination is sufficiently low. Although these conditions might seem to contradict the intuition that gene-specific selective sweeps require high recombination rates, they actually decrease the effective rate of recombination at loci affected by NFDS relative to the per-locus basal level, so that NFDS can cause gene-specific selective sweeps.ConclusionBecause many free-living prokaryotes are likely to evolve under NFDS caused by ubiquitous viruses, gene-specific selective sweeps driven by NFDS are expected to be a major, general phenomenon in prokaryotic populations.

【 授权许可】

CC BY   
© Takeuchi et al.; licensee BioMed Central. 2015

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