BioProject

Samples were collected with the aim of understanding the diversity and dynamics of microbial communities in the pristine environment of the basalt-hosted aquifers of Hellisheidi (SW Iceland). More...

Samples were collected with the aim of understanding the diversity and dynamics of microbial communities in the pristine environment of the basalt-hosted aquifers of Hellisheidi (SW Iceland). Our research group has been monitoring the microbial diversity in the different available deep wells since 2008, using bacterial and archaeal 16s rRNA gene cloning, 454-pyrosequencing (hypervariable regions V1-V3) and qPCR. The Hellisheidi site has different strategically located wells, used by Reykjavik Energy, the operator of the associated geothermal plant that has been performing CO2 and CO2-H2-H2S injections at a depth of 400–800 m and temperatures up to ~ 80°C as mitigation strategy for its main waste products. Preliminary results suggest that there is a diverse and abundant community before the injection. A large portion of the microorganisms belong likely to new species due to low similarity of the retrieved sequences to cultured microorganisms. Eukaryotes have not been detected in any of the analyzed samples. The pure CO2 injection caused a drastic change in the composition of the microbial community with a decrease of the diversity and richness. The Betaproteobacteria group, especially the Sideroxydans sp. (autotrophic iron and sulfur oxidizers) became dominant (March’12), showing a fast response of the microbial community to the pure CO2 injection. Two months later, we observed an important increase of the bacterial biomass (x500 factor) as measured by qPCR of the bacterial 16S rRNA gene along with a bloom of autotrophic sulfate-reducing bacteria (Desulfotomaculum sp., May’12). The increase of autotrophic microbial groups after the first injection suggests an enhancement of C fixation, and therefore, consequences for the nutrients cycling in this system. Less...