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ISME J. 2019 Aug 8. doi: 10.1038/s41396-019-0475-z. [Epub ahead of print]

Horizontally transmitted symbiont populations in deep-sea mussels are genetically isolated.

Author information

1
Genomic Microbiology Group, Institute of General Microbiology, Christian-Albrechts University, Kiel, Germany. dpicazo@ifam.uni-kiel.de.
2
Genomic Microbiology Group, Institute of General Microbiology, Christian-Albrechts University, Kiel, Germany.
3
Max Planck Institute for Marine Microbiology, Bremen, Germany.
4
Division of Microbiology and Ecosystem Science, University of Vienna, Wien, Austria.
5
Genomic Microbiology Group, Institute of General Microbiology, Christian-Albrechts University, Kiel, Germany. akupczok@ifam.uni-kiel.de.

Abstract

Eukaryotes are habitats for bacterial organisms where the host colonization and dispersal among individual hosts have consequences for the bacterial ecology and evolution. Vertical symbiont transmission leads to geographic isolation of the microbial population and consequently to genetic isolation of microbiotas from individual hosts. In contrast, the extent of geographic and genetic isolation of horizontally transmitted microbiota is poorly characterized. Here we show that chemosynthetic symbionts of individual Bathymodiolus brooksi mussels constitute genetically isolated subpopulations. The reconstruction of core genome-wide strains from high-resolution metagenomes revealed distinct phylogenetic clades. Nucleotide diversity and strain composition vary along the mussel life span and individual hosts show a high degree of genetic isolation. Our results suggest that the uptake of environmental bacteria is a restricted process in B. brooksi, where self-infection of the gill tissue results in serial founder effects during symbiont evolution. We conclude that bacterial colonization dynamics over the host life cycle is thus an important determinant of population structure and genome evolution of horizontally transmitted symbionts.

PMID:
31395952
DOI:
10.1038/s41396-019-0475-z

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