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New rRNA Gene-Based Phylogenies of the Alphaproteobacteria Provide Perspective on Major Groups, Mitochondrial Ancestry and Phylogenetic Instability

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Title New rRNA Gene-Based Phylogenies of the Alphaproteobacteria Provide Perspective on Major Groups, Mitochondrial Ancestry and Phylogenetic Instability
Names Ferla, Matteo P. (creator)
Thrash, J. Cameron (creator)
Giovannoni, Stephen J. (creator)
Patrick, Wayne M. (creator)
Date Issued 2013-12-11 (iso8601)
Note This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by the Public Library of Science. The published article can be found at: http://www.plosone.org/.
Abstract Bacteria in the class Alphaproteobacteria have a wide variety of lifestyles and physiologies. They include pathogens
of humans and livestock, agriculturally valuable strains, and several highly abundant marine groups. The ancestor of
mitochondria also originated in this clade. Despite significant effort to investigate the phylogeny of the
Alphaproteobacteria with a variety of methods, there remains considerable disparity in the placement of several
groups. Recent emphasis on phylogenies derived from multiple protein-coding genes remains contentious due to
disagreement over appropriate gene selection and the potential influences of systematic error. We revisited previous
investigations in this area using concatenated alignments of the small and large subunit (SSU and LSU) rRNA genes,
as we show here that these loci have much lower GC bias than whole genomes. This approach has allowed us to
update the canonical 16S rRNA gene tree of the Alphaproteobacteria with additional important taxa that were not
previously included, and with added resolution provided by concatenating the SSU and LSU genes. We investigated
the topological stability of the Alphaproteobacteria by varying alignment methods, rate models, taxon selection and
RY-recoding to circumvent GC content bias. We also introduce RYMK-recoding and show that it avoids some of the
information loss in RY-recoding. We demonstrate that the topology of the Alphaproteobacteria is sensitive to
inclusion of several groups of taxa, but it is less affected by the choice of alignment and rate methods. The majority of
topologies and comparative results from Approximately Unbiased tests provide support for positioning the
Rickettsiales and the mitochondrial branch within a clade. This composite clade is a sister group to the abundant
marine SAR11 clade (Pelagibacterales). Furthermore, we add support for taxonomic assignment of several recently
sequenced taxa. Accordingly, we propose three subclasses within the Alphaproteobacteria: the Caulobacteridae, the
Rickettsidae, and the Magnetococcidae.
Genre Article
Access Condition http://creativecommons.org/licenses/by/3.0/us/
Identifier Ferla MP, Thrash JC, Giovannoni SJ, Patrick WM (2013) New rRNA Gene-Based Phylogenies of the Alphaproteobacteria Provide Perspective on Major Groups, Mitochondrial Ancestry and Phylogenetic Instability. PLoS ONE 8(12): e83383. doi:10.1371/journal.pone.0083383

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