CO2 and carbonate as substrate for the activation of the microbial community in 180 m deep bedrock fracture fluid of Outokumpu Deep Drill Hole, Finland

Bomberg Malin (Corresponding Author), Mari Raulio, Sirpa Jylhä, Carsten W. Mueller, Carmen Höschen, Pauliina Rajala, Lotta Purkamo, Riikka Kietäväinen, Lasse Ahonen, Merja Itävaara

Research output: Contribution to journalArticleScientificpeer-review


Microbial communities in deep subsurface environments comprise a large portion of Earth's biomass, but the metabolic activities in these habitats are largely unknown. Here the effect of CO 2 and carbonate on the microbial community of an isolated groundwater fracture zone at 180 m depth of the Outokumpu Deep Scientific Drill Hole (Finland) was tested. Outokumpu groundwater at 180 m depth contains approximately 0.45 L L -1 dissolved gas of which methane contributes 76%. CO 2, on the other hand, is scarce. The number of microbial cells with intracellular activity in the groundwater was low when examined with redox staining. Fluorescence Assisted Cell Sorting (FACS) analyses indicated that only 1% of the microbial community stained active with the redox sensing dye in the untreated groundwater after 4 weeks of starvation. However, carbon substrate and sulfate addition increased the abundance of fluorescent cells up to 7%. CO 2 and CO 2 + sulfate activated the greatest number of microbes, especially increasing the abundance of Pseudomonas sp., which otherwise was present at only low abundance in Outokumpu. Over longer exposure time (2 months) up to 50% of the bacterial cells in the groundwater were shown to incorporate inorganic carbon from carbonate into biomass. Carbon recapture is an important feature in this ecosystem since it may decrease the rate of carbon loss in form of CO 2 released from cellular processes.

Original languageEnglish
Pages (from-to)846-871
Number of pages26
JournalAIMS Microbiology
Issue number4
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed



  • groundwater
  • crystalline bedrock
  • NanoSIMS
  • FACS
  • methane
  • sulfate
  • Pseudomonas
  • autotroph
  • Outokumpu

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