Evidence for extensive gene flow and Thermotoga subpopulations in subsurface and marine environments

Camilla L. Nesbø*, Kristen S. Swithers, Hakon Dahle, Thomas H.A. Haverkamp, Nils Kare Birkeland, Tatiana Sokolova, Ilya Kublanov, Olga Zhaxybayeva

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Oil reservoirs represent a nutrient-rich ecological niche of the deep biosphere. Although most oil reservoirs are occupied by microbial populations, when and how the microbes colonized these environments remains unanswered. To address this question, we compared 11 genomes of Thermotoga maritima-like hyperthermophilic bacteria from two environment types: subsurface oil reservoirs in the North Sea and Japan, and marine sites located in the Kuril Islands, Italy and the Azores. We complemented our genomes with Thermotoga DNA from publicly available subsurface metagenomes from North America and Australia. Our analysis revealed complex non-bifurcating evolutionary history of the isolates' genomes, suggesting high amounts of gene flow across all sampled locations, a conjecture supported by numerous recombination events. Genomes from the same type of environment tend to be more similar, and have exchanged more genes with each other than with geographically close isolates from different types of environments. Hence, Thermotoga populations of oil reservoirs do not appear isolated, a requirement of the 'burial and isolation' hypothesis, under which reservoir bacteria are descendants of the isolated communities buried with sediments that over time became oil reservoirs. Instead, our analysis supports a more complex view, where bacteria from subsurface and marine populations have been continuously migrating into the oil reservoirs and influencing their genetic composition. The Thermotoga spp. in the oil reservoirs in the North Sea and Japan probably entered the reservoirs shortly after they were formed. An Australian oil reservoir, on the other hand, was likely colonized very recently, perhaps during human reservoir development.

Original languageEnglish
Pages (from-to)1532-1542
Number of pages11
JournalISME Journal
Volume9
Issue number7
DOIs
StatePublished - 24 Jul 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015 International Society for Microbial Ecology.

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