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Title: The SAR11 Group of Alpha-Proteobacteria Is Not Related to the Origin of Mitochondria
Authors: Rodriguez-Ezpeleta, Naiara; Embley, T. Martin
Abstract: Although free living, members of the successful SAR11 group of marine alpha-proteobacteria contain a very small and A+T rich genome, two features that are typical of mitochondria and related obligate intracellular parasites such as the Rickettsiales. Previous phylogenetic analyses have suggested that Candidatus Pelagibacter ubique, the first cultured member of this group, is related to the Rickettsiales+mitochondria clade whereas others disagree with this conclusion. In order to determine the evolutionary position of the SAR11 group and its relationship to the origin of mitochondria, we have performed phylogenetic analyses on the concatenation of 24 proteins from 5 mitochondria and 71 proteobacteria. Our results support that SAR11 group is not the sistergroup of the Rickettsiales+mitochondria clade and confirm that the position of this group in the alpha-proteobacterial tree is strongly affected by tree reconstruction artefacts due to compositional bias. As a consequence, genome reduction and bias toward a high A+T content may have evolved independently in the SAR11 species, which points to a different direction in the quest for the closest relatives to mitochondria and Rickettsiales. In addition, our analyses raise doubts about the monophyly of the newly proposed Pelagibacteraceae family.
Issue Date: 2012
Type: Article
Language: English
DOI: 10.1371/journal.pone.0030520
ISSN: 1932-6203
Funder: Programa de Formacion de Investigadores del Departamento de Educacion, Universidades e Investigacion (Government of Basque Country)
Royal Society
Appears in Publication types:Artículos científicos

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