GBE The Genomic Diversification of the Whole Acinetobacter Genus: Origins, Mechanisms, and Consequences Marie Touchon1,2, Jean Cury1,2, Eun-Jeong Yoon3, Lenka Krizova4, Gustavo C. Cerqueira5, Cheryl Murphy5, Michael Feldgarden5, Jennifer Wortman5, Dominique Clermont6, Thierry Lambert3, Catherine Grillot-Courvalin3, Alexandr Nemec4,*, Patrice Courvalin3,*, and Eduardo P.C. Rocha1,2,* 1Microbial Evolutionary Genomics, Institut Pasteur, Paris, France 2CNRS, UMR3525, Paris, France 3Unite´ des Agents Antibacte´riens, Institut Pasteur, Paris, France 4Laboratory of Bacterial Genetics, National Institute of Public Health, Prague, Czech Republic. 5Broad Institute of Harvard and MIT, Cambridge, Massachusetts 6Collection de l’Institut Pasteur, Institut Pasteur, Paris, France *Corresponding author. E-mail:
[email protected],
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[email protected]. Accepted: October 6, 2014 Data deposition: This project has been deposited in GenBank according to the accession numbers provided in supplementary material online. Abstract Bacterial genomics has greatly expanded our understanding of microdiversification patterns within a species, but analyses at higher taxonomical levels are necessary to understand and predict the independent rise of pathogens in a genus. We have sampled, sequenced, and assessed the diversity of genomes of validly named and tentative species of the Acinetobacter genus, a clade including major nosocomial pathogens and biotechnologically important species. We inferred a robust global phylogeny and delimited several new putative species. The genus is very ancient and extremely diverse: Genomes of highly divergent species share more orthologs than certain strains within a species. We systematically characterized elements and mechanisms driving genome diversification, such as conjugative elements, insertion sequences, and natural transformation. We found many error-prone polymerases that may play a role in resistance to toxins, antibiotics, and in the generation of genetic variation.