Dynamics of genome change among Legionella species

• Type of Material: Article
• Authors: Sandeep J. Joseph, Emory University; Daniel Cox, Emory University; Bernard Wolff, Centers for Disease Control and Prevention; Shatavia S. Morrison, Centers for Disease Control and Prevention; Natalia A. Kozak-Muiznieks, Centers for Disease Control and Prevention; Michael Frace, Centers for Disease Control and Prevention; Xavier Didelot, Imperial College London; Santiago Castillo-Ramirez, Universidad Nacional Autónoma de México; Jonas Winchell, Centers for Disease Control and Prevention; Timothy Read, Emory University; Deborah Dean, University of California, San Francisco
• Language: English
• Date: 2016-09-16
• Publisher: Nature Publishing Group
• Publication Version: Final Published Version
• Copyright Statement: © 2016 The Author(s).
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1038/srep33442
• Title of Journal or Parent Work: Scientific Reports
• ISSN: 2045-2322
• Volume: 6
• Start Page: 33442
• End Page: 33442
• Grant/Funding Information: This research was funded in part by Public Health Service grant from the National Institutes of Health R01 AI098843 (to D.D.) and by the Advanced Molecular Detection initiative of the CDC (J.W.).
• Keywords: LEGIONNAIRES-DISEASE; COMMUNITY-ACQUIRED PNEUMONIA; POPULATION-STRUCTURE; HIGH-THROUGHPUT; Phylogenetics; HORIZONTAL GENE-TRANSFER; PNEUMOPHILA; RECOMBINATION; PHYLOGENETIC ANALYSIS; Science & Technology; Microbial genetics; PONTIAC FEVER; Multidisciplinary Sciences; STAPHYLOCOCCUS-AUREUS
• Research Categories: Biology, Microbiology; Biology, Genetics; Health Sciences, General

Abstract

Legionella species inhabit freshwater and soil ecosystems where they parasitize protozoa. L. pneumonphila (LP) serogroup-1 (Lp1) is the major cause of Legionnaires' Disease (LD), a life-threatening pulmonary infection that can spread systemically. The increased global frequency of LD caused by Lp and non-Lp species underscores the need to expand our knowledge of evolutionary forces underlying disease pathogenesis. Whole genome analyses of 43 strains, including all known Lp serogroups 1-17 and 17 emergent LD-causing Legionella species (of which 33 were sequenced in this study) in addition to 10 publicly available genomes, resolved the strains into four phylogenetic clades along host virulence demarcations. Clade-specific genes were distinct for genetic exchange and signal-transduction, indicating adaptation to specific cellular and/or environmental niches. CRISPR spacer comparisons hinted at larger pools of accessory DNA sequences in Lp than predicted by the pan-genome analyses. While recombination within Lp was frequent and has been reported previously, population structure analysis identified surprisingly few DNA admixture events between species. In summary, diverse Legionella LD-causing species share a conserved core-genome, are genetically isolated from each other, and selectively acquire genes with potential for enhanced virulence.