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Comparative and Functional Genomics
Volume 2009, Article ID 510270, 5 pages
http://dx.doi.org/10.1155/2009/510270
Research Article

Evidence of Extensive Homologous Recombination in the Core Genome of Rickettsia

1Institute of Biomedical Informatics/Zhejiang Provincial Key Laboratory of Medical Genetics, Wenzhou Medical College, Wenzhou 325035, China
2Center for Comparative Genomics and Bioinformatics, Department of Biochemistry and Molecular Biology, Pennsylvania State University, PA 16802, USA

Received 3 February 2009; Accepted 11 April 2009

Academic Editor: James Thomas

Copyright © 2009 Jinyu Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The important role of homologous recombination has been extensively demonstrated to be fundamental for genetic variation in bacterial genomes. In contrast to extracellular or facultative intracellular bacteria, obligate intracellular bacteria are considered to be less prone to recombination, especially for their core genomes. In Rickettsia, only antigen-related genes were identified to have experienced homologous recombination. In this study, we employed evolutionary genomic approaches to investigate the impact of recombination on the core genome of Rickettsia. Phylogenetic network and phylogenetic compatibility matrix analyses are clearly consistent with the hypothesis that recombination has occurred frequently during Rickettsia evolution. 28% of Rickettsia core genes (194 out of 690) are found to present the evidence of recombination under four independent statistical methods. Further functional classification shows that these recombination events occur across all functional categories, with a significant overrepresentation in the cell wall/membrane/envelope biogenesis, which may provide a molecular basis for the parasite adaptation to host immunity. This evolutionary genomic analysis provides insight into the substantial role of recombination in the evolution of the intracellular pathogenic bacteria Rickettsia.