Genetic structure of marine Borrelia garinii and population admixture with the terrestrial cycle of Lyme borreliosis
Article first published online: 8 JUN 2011
© 2011 Society for Applied Microbiology and Blackwell Publishing Ltd
Volume 13, Issue 9, pages 2453–2467, September 2011
How to Cite
Gómez-Díaz, E., Boulinier, T., Sertour, N., Cornet, M., Ferquel, E. and McCoy, K. D. (2011), Genetic structure of marine Borrelia garinii and population admixture with the terrestrial cycle of Lyme borreliosis. Environmental Microbiology, 13: 2453–2467. doi: 10.1111/j.1462-2920.2011.02515.x
- Issue published online: 12 SEP 2011
- Article first published online: 8 JUN 2011
- Received 1 December, 2010; accepted 20 April, 2011.
Despite the importance of population structure for the epidemiology of pathogenic bacteria, the spatial and ecological heterogeneity of these populations is often poorly characterized. Here, we investigated the genetic diversity and population structure of the Lyme borreliosis (LB) spirochaete Borrelia garinii in its marine cycle involving colonial seabirds and different host races of the seabird tick Ixodes uriae. Multilocus sequence analyses (MLSA) on eight chromosomal and two plasmid loci (ospA and ospC) indicate that B. garinii circulating in the marine system is highly diverse. Microevolution in marine B. garinii seems to be mainly clonal, but recombination and selection do occur. Sequence types were not evenly distributed among geographic regions, with substantial population subdivision between Atlantic and Pacific Ocean basins. However, no geographic structuring was evident within regions. Results of selection analyses and phylogenetic discordance between chromosomal and plasmid loci indicate adaptive evolution is likely occurring in this system, but no pattern of host or vector-associated divergence was found. Recombination analyses showed evidence for population admixture between terrestrial and marine strains, suggesting that LB spirochaetes are exchanged between these enzootic cycles. Importantly, our results highlight the need to explicitly consider the marine system for a complete understanding of the evolutionary ecology and global epidemiology of Lyme borreliosis.