A divide-and-conquer phylogenomic approach based on character supermatrices resolves early steps in the evolution of the Archaea.

BACKGROUND: The recent rise in cultivation-independent genome sequencing has provided key material to explore uncharted branches of the Tree of Life. This has been particularly spectacular concerning the Archaea, projecting them at the center stage as prominently relevant to understand early stages in evolution and the emergence of fundamental metabolisms as well as the origin of eukaryotes. Yet, resolving deep divergences remains a challenging task due to well-known tree-reconstruction artefacts and biases in extracting robust ancient phylogenetic signal, notably when analyzing data sets including the three Domains of Life. Among the various strategies aimed at mitigating these problems, divide-and-conquer approaches remain poorly explored, and have been primarily based on reconciliation among single gene trees which however notoriously lack ancient phylogenetic signal. RESULTS: We analyzed sub-sets of full supermatrices covering the whole Tree of Life with specific taxonomic sampling to robustly resolve different parts of the archaeal phylogeny in light of their current diversity. Our results strongly support the existence and early emergence of two main clades, Cluster I and Cluster II, which we name Ouranosarchaea and Gaiarchaea, and we clarify the placement of important novel archaeal lineages within these two clades. However, the monophyly and branching of the fast evolving nanosized DPANN members remains unclear and worth of further study. CONCLUSIONS: We inferred a well resolved rooted phylogeny of the Archaea that includes all recently described phyla of high taxonomic rank. This phylogeny represents a valuable reference to study the evolutionary events associated to the early steps of the diversification of the archaeal domain. Beyond the specifics of archaeal phylogeny, our results demonstrate the power of divide-and-conquer approaches to resolve deep phylogenetic relationships, which should be applied to progressively resolve the entire Tree of Life.

GeneSpy, a user-friendly and flexible genomic context visualizer.

Summary: The exploration and comparison of genome organization is routinely used in the frame of genomic and phylogenomic analyses. As a consequence, in the past few years, various tools allowing visualizing genomic contexts have been developed. However, their use is often hampered by a lack of flexibility, particularly concerning associated databases input formats and figure customization. Here we present GeneSpy, a graphical user interface that allows the visualization and dynamic exploration of eukaryotic and prokaryotic annotated genomes. GeneSpy relies on user-friendly manageable local databases and allows the easy customization and production of figures in a multitude of formats. Availability and implementation: GeneSpy is freely available at https://lbbe.univ-lyon1.fr/GeneSpy/ for Linux, Mac OS and Windows under CeCILL license (http://www.cecill.info/licences/). It is written in Python 2.7 and depends on Matplotlib, Tkinter and Sqlite libraries. Supplementary information: Supplementary data are available at Bioinformatics online.

RiboDB Database: A Comprehensive Resource for Prokaryotic Systematics.

Ribosomal proteins (r-proteins) are increasingly used as an alternative to ribosomal rRNA for prokaryotic systematics. However, their routine use is difficult because r-proteins are often not or wrongly annotated in complete genome sequences, and there is currently no dedicated exhaustive database of r-proteins. RiboDB aims at fulfilling this gap. This weekly updated comprehensive database allows the fast and easy retrieval of r-protein sequences from publicly available complete prokaryotic genome sequences. The current version of RiboDB contains 90 r-proteins from 3,750 prokaryotic complete genomes encompassing 38 phyla/major classes and 1,759 different species. RiboDB is accessible at http://ribodb.univ-lyon1.fr and through ACNUC interfaces.