Lineage specific recombination rates and microevolution in Listeria monocytogenes
den Bakker, Henk C., Didelot, Xavier, Fortes, Esther D, Nightingale, Kendra K and Wiedmann, Martin. (2008) Lineage specific recombination rates and microevolution in Listeria monocytogenes. BMC Evolutionary Biology, Vol. 8 (No. 27). ISSN 1471-2148
WRAP_Didelot_Lineage_specific_1471-2148-8-277.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Official URL: http://dx.doi.org/10.1186/1471-2148-8-277
Background: The bacterium Listeria monocytogenes is a saprotroph as well as an opportunistic human foodborne pathogen, which has previously been shown to consist of at least two widespread lineages (termed lineages I and II) and an uncommon lineage (lineage III). While some L. monocytogenes strains show evidence for considerable diversification by homologous recombination, our understanding of the contribution of recombination to L. monocytogenes evolution is still limited. We therefore used
STRUCTURE and ClonalFrame, two programs that model the effect of recombination, to make inferences about the population structure and different aspects of the recombination process in L. monocytogenes. Analyses were performed using sequences for seven loci (including the house-keeping genes gap, prs, purM and ribC, the stress response gene sigB, and the virulence genes actA and inlA) for 195 L. monocytogenes isolates.
Results: Sequence analyses with ClonalFrame and the Sawyer's test showed that recombination is more
prevalent in lineage II than lineage I and is most frequent in two house-keeping genes (ribC and purM) and the two virulence genes (actA and inlA). The relative occurrence of recombination versus point mutation is about six times higher in lineage II than in lineage I, which causes a higher genetic variability in lineage II. Unlike lineage I, lineage II represents a genetically heterogeneous population with a relatively high proportion (30% average) of genetic material imported from external sources. Phylograms, constructed with correcting for recombination, as well as Tajima's D data suggest that both lineages I and II have suffered a population bottleneck.
Conclusion: Our study shows that evolutionary lineages within a single bacterial species can differ
considerably in the relative contributions of recombination to genetic diversification. Accounting for recombination in phylogenetic studies is critical, and new evolutionary models that account for the possibility of changes in the rate of recombination would be required. While previous studies suggested that only L. monocytogenes lineage I has experienced a recent bottleneck, our analyses clearly show that lineage II experienced a bottleneck at about the same time, which was subsequently obscured by abundant
homologous recombination after the lineage II bottleneck. While lineage I and lineage II should be considered separate species from an evolutionary viewpoint, maintaining single species name may be warranted since both lineages cause the same type of human disease.
|Item Type:||Journal Article|
|Subjects:||Q Science > QR Microbiology|
|Divisions:||Faculty of Science > Statistics|
|Library of Congress Subject Headings (LCSH):||Listeria monocytogenes, Pathogenic microorganisms, Evolutionary genetics|
|Journal or Publication Title:||BMC Evolutionary Biology|
|Publisher:||BioMed Central Ltd.|
|Official Date:||8 October 2008|
|Access rights to Published version:||Open Access|
|Funder:||United States. Dept. of Agriculture. Cooperative State Research, Education and Extension Service (CSREES)|
|Grant number:||2005-34459-15625 (CSREES), NYC-143451 (CSREES)|
1. Gray M, Freitag N, Boor K: How the bacterial pathogen Listeria
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