Burkholderia pseudomallei sequencing identifies genomic clades with distinct recombination, accessory, and epigenetic profiles
Abstract
Burkholderia pseudomallei (Bp) is the causative agent of the infectious disease melioidosis. To investigate population diversity, recombination, and horizontal gene transfer in closely related Bp isolates, we performed whole-genome sequencing (WGS) on 106 clinical, animal, and environmental strains from a restricted Asian locale. Whole-genome phylogenies resolved multiple genomic clades of Bp, largely congruent with multilocus sequence typing (MLST). We discovered widespread recombination in the Bp core genome, involving hundreds of regions associated with multiple haplotypes. Highly recombinant regions exhibited functional enrichments that may contribute to virulence. We observed clade-specific patterns of recombination and accessory gene exchange, and provide evidence that this is likely due to ongoing recombination between clade members. Reciprocally, interclade exchanges were rarely observed, suggesting mechanisms restricting gene flow between clades. Interrogation of accessory elements revealed that each clade harbored a distinct complement of restriction-modification (RM) systems, predicted to cause clade-specific patterns of DNA methylation. Using methylome sequencing, we confirmed that representative strains from separate clades indeed exhibit distinct methylation profiles. Finally, using an E. coli system, we demonstrate that Bp RM systems can inhibit uptake of non-self DNA. Our data suggest that RM systems borne on mobile elements, besides preventing foreign DNA invasion, may also contribute to limiting exchanges of genetic material between individuals of the same species. Genomic clades may thus represent functional units of genetic isolation in Bp, modulating intraspecies genetic diversity.
Citation
Nandi , T , Holden , M , Didelot , X , Mehershahi , K , Boddey , J A , Beacham , I , Peak , I , Harting , J , Baybayan , P , Guo , Y , Wang , S , How , L C , Sim , B , Essex-Lopresti , A , Sarkar-Tyson , M , Nelson , M , Smither , S , Ong , C , Aw , L T , Hoon , C H , Michell , S , Studholme , D J , Titball , R , Chen , S L , Parkhill , J & Tan , P 2015 , ' Burkholderia pseudomallei sequencing identifies genomic clades with distinct recombination, accessory, and epigenetic profiles ' , Genome Research , vol. 25 , no. 1 , pp. 129-141 . https://doi.org/10.1101/gr.177543.114
Publication
Genome Research
Status
Peer reviewed
ISSN
1088-9051Type
Journal article
Rights
© 2015 Nandi et al.; Published by Cold Spring Harbor Laboratory Press. This article is distributed exclusively by Cold Spring Harbor Laboratory Press for the first six months after the full-issue publication date (see http://genome.cshlp.org/site/misc/terms.xhtml). After six months, it is available under a Creative Commons License (Attribution-NonCommercial 4.0 International), as described at http://creativecommons.org/licenses/by-nc/4.0/.
Description
This study was supported by a core grant to P.T. from the GIS, an A-STAR research institute. The sequencing of the Burkholderia pseudomallei strains was supported by Wellcome Trust grant 098051 to J.P.Collections
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