MBE Advance Access originally published online on November 13, 2008
Molecular Biology and Evolution 2009 26(2):385-397; doi:10.1093/molbev/msn264
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Research Articles |
Rapid Evolution and the Importance of Recombination to the Gastroenteric Pathogen Campylobacter jejuni
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* Department of Maths and Statistics, Lancaster University, Lancaster, United Kingdom
Department of Medicine, Lancaster University, Lancaster, United Kingdom
Faculty of Veterinary Science, University of Liverpool, Leahurst, Neston, United Kingdom
Preston Microbiology Services, Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust, Preston, United Kingdom
|| Manchester Medical Microbiology Partnership, P.O. Box 209, Clinical Sciences Building, Manchester Royal Infirmary, Manchester, United Kingdom
¶ Division of Medical Microbiology, School of Infection and Host Defence, University of Liverpool, Liverpool, United Kingdom
E-mail: djw{at}uchicago.edu.
Accepted for publication November 6, 2008.
Responsible for the majority of bacterial gastroenteritis in the developed world, Campylobacter jejuni is a pervasive pathogen of humans and animals, but its evolution is obscure. In this paper, we exploit contemporary genetic diversity and empirical evidence to piece together the evolutionary history of C. jejuni and quantify its evolutionary potential. Our combined population genetics–phylogenetics approach reveals a surprising picture. Campylobacter jejuni is a rapidly evolving species, subject to intense purifying selection that purges 60% of novel variation, but possessing a massive evolutionary potential. The low mutation rate is offset by a large effective population size so that a mutation at any site can occur somewhere in the population within the space of a week. Recombination has a fundamental role, generating diversity at twice the rate of de novo mutation, and facilitating gene flow between C. jejuni and its sister species Campylobacter coli. We attempt to calibrate the rate of molecular evolution in C. jejuni based solely on within-species variation. The rates we obtain are up to 1,000 times faster than conventional estimates, placing the C. jejuni–C. coli split at the time of the Neolithic revolution. We weigh the plausibility of such recent bacterial evolution against alternative explanations and discuss the evidence required to settle the issue.
Key Words: Campylobacter jejuni • molecular clock • recombination • selection • coalescent • Neolithic
1 Present address: Department of Human Genetics, University of Chicago, 920 East 58th Street, CLSC 410, Chicago, IL 60637 USA.
2 Present address: Université d'Avignon, IUT STID, Site Agroparc, BP 1207, Avignon, France.
Rasmus Nielsen, Associate Editor
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