Evidence for genetic drift in the diversification of a geographically isolated population of the hyperthermophilic archaeon Pyrococcus

Genetic drift is a mechanism of population divergence that is important in the evolution of plants and animals but is thought to be rare in free-living microorganisms because of their typically large population sizes and unrestricted means of dispersal. We used both phylogenetic and insertion sequen...

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Bibliographic Details
Published in:Molecular biology and evolution 2005-11, Vol.22 (11), p.2297-2303
Main Authors: Escobar-Páramo, Patricia, Ghosh, Sulagna, DiRuggiero, Jocelyne
Format: Article
Language:English
Subjects:
Archaea
Base Sequence
Blotting, Southern
Cluster Analysis
DNA Primers
DNA Transposable Elements - genetics
Evolution, Molecular
Genetic Drift
Genetic Variation
Genetics, Population
Geography
Likelihood Functions
Marine
Mediterranean Sea
Models, Genetic
Molecular Sequence Data
Pacific Ocean
Phylogeny
Pyrococcus
Pyrococcus - genetics
Sequence Analysis, DNA
Species Specificity
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Summary:Genetic drift is a mechanism of population divergence that is important in the evolution of plants and animals but is thought to be rare in free-living microorganisms because of their typically large population sizes and unrestricted means of dispersal. We used both phylogenetic and insertion sequence (IS) element analyses in hyperthermophilic archaea of the genus Pyrococcus to test the hypothesis that genetic drift played an important role in the diversification of these microorganisms. Multilocus sequence typing of a collection of 36 isolates of Pyrococcus, from different hydrothermal systems in the Pacific Ocean and the Mediterranean Sea, revealed that Pyrococcus populations from different geographic locations are genetically differentiated. Analysis of IS elements in these isolates exposed their presence in all individuals of only one geographically isolated lineage, that of Vulcano Island in the Mediterranean Sea. Detailed sequence analysis of six selected IS elements in the Vulcano population showed that these elements cause deleterious genomic alterations, including inactivation of gene function. The high frequency of IS elements in the sampled population together with their observed harmful effects in the genome of Pyrococcus provide molecular evidence that the Vulcano Island population of Pyrococcus is geographically isolated and that those genetic mobile elements have been brought up to high frequency by genetic drift. Thus, genetic drift resulting from physical isolation should be considered as a factor influencing differentiation in prokaryotes.
ISSN:0737-4038
1537-1719
DOI:10.1093/molbev/msi227