Rapid Evolution and the Importance of Recombination to the Gastroenteric Pathogen Campylobacter jejuni

• Published in: Molecular biology and evolution Vol. 26; no. 2; pp. 385 - 397
• Main Authors: Wilson, Daniel J., Gabriel, Edith, Leatherbarrow, Andrew J.H., Cheesbrough, John, Gee, Steven, Bolton, Eric, Fox, Andrew, Hart, C. Anthony, Diggle, Peter J., Fearnhead, Paul
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01.02.2009
• Subjects: Bacteria; Biodiversity; Campylobacter; Campylobacter coli; Campylobacter coli - genetics; Campylobacter Infections - microbiology; Campylobacter jejuni; Campylobacter jejuni - classification; Campylobacter jejuni - genetics; England; Evolution; Evolution, Molecular; Evolutionary biology; Evolutionary genetics; Gastroenteritis; Gene flow; Genetic diversity; Genetic Drift; Genetic recombination; Genetic Speciation; Genetics; Humans; Molecular biology; Molecular evolution; Mutation; Mutation rates; Pathogens; Population genetics; Population number; Recombination; Recombination, Genetic; Selection, Genetic; Sibling species; Stone Age; England; molecular clock; recombination; selection; Neolithic; coalescent
• ISSN: 0737-4038; 1537-1719; 1537-1719
• DOI: 10.1093/molbev/msn264

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.