title: Mycobacterial phylogenomics: an enhanced method for gene turnover analysis reveals uneven levels of gene gain and loss among species and gene families.
abstract: Species of the genus Mycobacterium differ in several features, from geographic ranges, and degree of pathogenicity, to ecological and host preferences. The recent availability of several fully sequenced genomes for a number of these species enabled the comparative study of the genetic determinants of this wide lifestyle diversity. Here, we applied two complementary phylogenetic-based approaches using information from 19 Mycobacterium genomes to obtain a more comprehensive view of the evolution of this genus. First, we inferred the phylogenetic relationships using two new approaches, one based on a Mycobacterium-specific amino acid substitution matrix and the other on a gene content dissimilarity matrix. Then, we utilized our recently developed gain-and-death stochastic models to study gene turnover dynamics in this genus in a maximum-likelihood framework. We uncovered a scenario that differs markedly from traditional 16S rRNA data and improves upon recent phylogenomic approaches. We also found that the rates of gene gain and death are high and unevenly distributed both across species and across gene families, further supporting the utility of the new models of rate heterogeneity applied in a phylogenetic context. Finally, the functional annotation of the most expanded or contracted gene families revealed that the transposable elements and the fatty acid metabolism-related gene families are the most important drivers of gene content evolution in Mycobacterium.
authors.affiliation: Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Librado
authors.affiliation: Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, SpainDepartment of Integrative Biology, University of California, Berkeley.
authors.forename: Filipe G
authors.initials: FG
authors.lastname: Vieira
authors.affiliation: Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sánchez-Gracia
authors.affiliation: Department of Biological Sciences, Fordham UniversitySackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York.
authors.forename: Sergios-Orestis
authors.initials: SO
authors.lastname: Kolokotronis
authors.affiliation: Departament de Genètica and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain jrozas@ub.edu.
authors.forename: Julio
authors.initials: J
authors.lastname: Rozas
mesh_terms: D019143:Evolution, Molecular; D016680:Genome, Bacterial; D009161:Mycobacterium / Q000235:genetics*; D010802:Phylogeny
keywords: M. tuberculosis; gene families; gene gain and loss; gene turnover rates; maximum likelihood; rate heterogeneity