Ultradeep microbial communities at 4.4 km within crystalline bedrock: Implications for habitability in a planetary context

Lotta Purkamo (Corresponding Author), Riikka Kietäväinen, Maija Nuppunen-Puputti, Malin Bomberg, Claire Cousins

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The deep bedrock surroundings are an analog for extraterrestrial habitats for life. In this study, we investigated microbial life within anoxic ultradeep boreholes in Precambrian bedrock, including the adaptation to environmental conditions and lifestyle of these organisms. Samples were collected from Pyhäsalmi mine environment in central Finland and from geothermal drilling wells in Otaniemi, Espoo, in southern Finland. Microbial communities inhabiting the up to 4.4 km deep bedrock were characterized with phylogenetic marker gene (16S rRNA genes and fungal ITS region) amplicon and DNA and cDNA metagenomic sequencing. Functional marker genes (dsrB, mcrA, narG) were quantified with qPCR. Results showed that although crystalline bedrock provides very limited substrates for life, the microbial communities are diverse. Gammaproteobacterial phylotypes were most dominant in both studied sites. Alkanindiges-affiliating OTU was dominating in Pyhäsalmi fluids, while different depths of Otaniemi samples were dominated by Pseudomonas. One of the most common OTUs detected from Otaniemi could only be classified to phylum level, highlighting the uncharacterized nature of the deep biosphere in bedrock. Chemoheterotrophy, fermentation and nitrogen cycling are potentially significant metabolisms in these ultradeep environments. To conclude, this study provides information on microbial ecology of low biomass, carbon-depleted and energy-deprived deep subsurface environment. This information is useful in the prospect of finding life in other planetary bodies.

Original languageEnglish
Article number2
JournalLife
Volume10
Issue number1
DOIs
Publication statusPublished - Mar 2020
MoE publication typeA1 Journal article-refereed

Fingerprint

habitability
bedrock
microbial communities
microbial community
Genes
Finland
Crystalline materials
genes
Exobiology
Metagenomics
markers
Ecology
gene
Pseudomonas
Boreholes
rRNA Genes
Metabolism
Biomass
Fermentation
Ecosystem

Keywords

  • Bedrock
  • Deep biosphere
  • Deep subsurface
  • Environmental microbiology
  • Extraterrestrial habitat analog
  • Low biomass
  • Microbial community
  • Microbial ecology

Cite this

Purkamo, Lotta ; Kietäväinen, Riikka ; Nuppunen-Puputti, Maija ; Bomberg, Malin ; Cousins, Claire. / Ultradeep microbial communities at 4.4 km within crystalline bedrock : Implications for habitability in a planetary context. In: Life. 2020 ; Vol. 10, No. 1.
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abstract = "The deep bedrock surroundings are an analog for extraterrestrial habitats for life. In this study, we investigated microbial life within anoxic ultradeep boreholes in Precambrian bedrock, including the adaptation to environmental conditions and lifestyle of these organisms. Samples were collected from Pyh{\"a}salmi mine environment in central Finland and from geothermal drilling wells in Otaniemi, Espoo, in southern Finland. Microbial communities inhabiting the up to 4.4 km deep bedrock were characterized with phylogenetic marker gene (16S rRNA genes and fungal ITS region) amplicon and DNA and cDNA metagenomic sequencing. Functional marker genes (dsrB, mcrA, narG) were quantified with qPCR. Results showed that although crystalline bedrock provides very limited substrates for life, the microbial communities are diverse. Gammaproteobacterial phylotypes were most dominant in both studied sites. Alkanindiges-affiliating OTU was dominating in Pyh{\"a}salmi fluids, while different depths of Otaniemi samples were dominated by Pseudomonas. One of the most common OTUs detected from Otaniemi could only be classified to phylum level, highlighting the uncharacterized nature of the deep biosphere in bedrock. Chemoheterotrophy, fermentation and nitrogen cycling are potentially significant metabolisms in these ultradeep environments. To conclude, this study provides information on microbial ecology of low biomass, carbon-depleted and energy-deprived deep subsurface environment. This information is useful in the prospect of finding life in other planetary bodies.",
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Ultradeep microbial communities at 4.4 km within crystalline bedrock : Implications for habitability in a planetary context. / Purkamo, Lotta (Corresponding Author); Kietäväinen, Riikka; Nuppunen-Puputti, Maija; Bomberg, Malin; Cousins, Claire.

In: Life, Vol. 10, No. 1, 2, 03.2020.

Research output: Contribution to journalArticleScientificpeer-review

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