Trajectories and Drivers of Genome Evolution in Surface-Associated Marine Phaeobacter

Heike M. Freese*, Johannes Sikorski, Boyke Bunk, Carmen Scheuner, Jan P. Meier-Kolthoff, Cathrin Sproeer, Lone Gram, Joerg Overmann

*Corresponding author for this work

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The extent of genome divergence and the evolutionary events leading to speciation of marine bacteria have mostly been studied for (locally) abundant, free-living groups. The genus Phaeobacter is found on different marine surfaces, seems to occupy geographically disjunct habitats, and is involved in different biotic interactions, and was therefore targeted in the present study. The analysis of the chromosomes of 32 closely related but geographically spread Phaeobacter strains revealed an exceptionally large, highly syntenic core genome. The flexible gene pool is constantly but slightly expanding across all Phaeobacter lineages. The horizontally transferred genes mostly originated from bacteria of the Roseobacter group and horizontal transfer most likely was mediated by gene transfer agents. No evidence for geographic isolation and habitat specificity of the different phylogenomic Phaeobacter clades was detected based on the sources of isolation. In contrast, the functional gene repertoire and physiological traits of different phylogenomic Phaeobacter clades were sufficiently distinct to suggest an adaptation to an associated lifestyle with algae, to additional nutrient sources, or toxic heavy metals. Our study reveals that the evolutionary trajectories of surface-associated marine bacteria can differ significantly from free-living marine bacteria or marine generalists.
Original languageEnglish
JournalGenome Biology and Evolution
Issue number12
Pages (from-to)3297-3311
Publication statusPublished - 2017

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This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact


  • Bacterial adaptation
  • Ecological niche
  • Gene flow
  • Gene transfer agent
  • Horizontal gene transfer
  • Population genomics


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