Characterization of bacterial diversity to a depth of 1500 m in the Outokumpu deep borehole, Fennoscandian Shield

Merja Itävaara (Corresponding Author), Mari Nyyssönen, Anu Kapanen, Aura Nousiainen, Lasse Ahonen, Ilmo Kukkonen

Research output: Contribution to journalArticleScientificpeer-review

80 Citations (Scopus)

Abstract

This paper demonstrates the first microbiological sampling of the Outokumpu deep borehole (2516 m deep) aiming at characterizing the bacterial community composition and diversity of sulphate-reducing bacteria (SRB) in Finnish crystalline bedrock aquifers. Sampling was performed using a 1500-m-long pressure-tight tube that provided 15 subsamples, each corresponding to a 100-m section down the borehole. Microbial density measurements, as well as community fingerprinting with 16S rRNA gene-based denaturing gradient gel electrophoresis, demonstrated that microbial communities in the borehole water varied as a function of sampling depth. In the upper part of the borehole, bacteria affiliated to the family Comamonadaceae dominated the bacterial community. Further down the borehole, bacteria affiliated to the class Firmicutes became more prominent and, according to 16S rRNA gene clone libraries, dominated the bacterial community at 1400–1500 m. In addition, the largest number of bacterial classes was observed at 1400–1500 m. The dsrB genes detected in the upper part of the borehole were more similar to the dsrB genes of cultured SRBs, such as the genus Desulfotomaculum, whereas in the deeper parts of the borehole, the dsrB genes were more closely related to the uncultured bacteria that have been detected earlier in deep earth crust aquifers.
Original languageEnglish
Pages (from-to)295-309
Number of pages15
JournalFEMS Microbiology Ecology
Volume77
Issue number2
DOIs
Publication statusPublished - 2011
MoE publication typeA1 Journal article-refereed

Keywords

  • terrestrial deep biosphere
  • crystalline bedrock
  • extremophiles
  • saline groundwater
  • microbial diversity

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