Extensive diversity of Rickettsiales bacteria in two species of ticks from China and the evolution of the RickettsialesReport as inadecuate




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BMC Evolutionary Biology

, 14:167

Phylogenetics and phylogeography

Abstract

BackgroundBacteria of the order Rickettsiales Alphaproteobacteria are obligate intracellular parasites that infect species from virtually every major eukaryotic lineage. Several rickettsial genera harbor species that are significant emerging and re-emerging pathogens of humans. As species of Rickettsiales are associated with an extremely diverse host range, a better understanding of the historical associations between these bacteria and their hosts will provide important information on their evolutionary trajectories and, particularly, their potential emergence as pathogens.

ResultsNine species of Rickettsiales two in the genus Rickettsia, three in the genus Anaplasma, and four in the genus Ehrlichia were identified in two species of hard ticks Dermacentor nuttalli and Hyalomma asiaticum from two geographic regions in Xinjiang through genetic analyses of 16S rRNA, gltA, and groEL gene sequences. Notably, two lineages of Ehrlichia and one lineage of Anaplasma were distinct from any known Rickettsiales, suggesting the presence of potentially novel species in ticks in Xinjiang. Our phylogenetic analyses revealed some topological differences between the phylogenies of the bacteria and their vectors, which led us to marginally reject a model of exclusive bacteria-vector co-divergence.

ConclusionsTicks are an important natural reservoir of many diverse species of Rickettsiales. In this work, we identified a single tick species that harbors multiple species of Rickettsiales, and uncovered extensive genetic diversity of these bacteria in two tick species from Xinjiang. Both bacteria-vector co-divergence and cross-species transmission appear to have played important roles in Rickettsiales evolution.

KeywordsCo-divergence Evolution Phylogeny Rickettsiales bacteria Ticks Vectors Electronic supplementary materialThe online version of this article doi:10.1186-s12862-014-0167-2 contains supplementary material, which is available to authorized users.

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Author: Yan-Jun Kang - Xiu-Nian Diao - Gao-Yu Zhao - Ming-Hui Chen - Yanwen Xiong - Mang Shi - Wei-Ming Fu - Yu-Jiang Guo - Bao P

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