Active Microbial Communities Inhabit Sulphate-Methane Interphase in Deep Bedrock Fracture Fluids in Olkiluoto, Finland

Abstract

Active microbial communities of deep crystalline bedrock fracture water were investigated from seven different boreholes in Olkiluoto (Western Finland) using bacterial and archaeal 16S rRNA, dsrB, and mcrA gene transcript targeted 454 pyrosequencing. Over a depth range of 296–798 m below ground surface the microbial communities changed according to depth, salinity gradient, and sulphate and methane concentrations. The highest bacterial diversity was observed in the sulphate-methane mixing zone (SMMZ) at 250–350 m depth, whereas archaeal diversity was highest in the lowest boundaries of the SMMZ. Sulphide-oxidizing ε-proteobacteria (Sulfurimonas sp.) dominated in the SMMZ and γ-proteobacteria (Pseudomonas spp.) below the SMMZ. The active archaeal communities consisted mostly of ANME-2D and Thermoplasmatales groups, although Methermicoccaceae, Methanobacteriaceae, and Thermoplasmatales (SAGMEG, TMG) were more common at 415–559 m depth. Typical indicator microorganisms for sulphate-methane transition zones in marine sediments, such as ANME-1 archaea, α-, β- and δ-proteobacteria, JS1, Actinomycetes, Planctomycetes, Chloroflexi, and MBGB Crenarchaeota were detected at specific depths. DsrB genes were most numerous and most actively transcribed in the SMMZ while the mcrA gene concentration was highest in the deep methane rich groundwater. Our results demonstrate that active and highly diverse but sparse and stratified microbial communities inhabit the Fennoscandian deep bedrock ecosystems.

Rare Biosphere Archaea Assimilate Acetate in Precambrian Terrestrial Subsurface at 2.2 km Depth

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“…The preparation of the barcoded bacterial 16S rRNA gene amplicons was carried out by single round PCR using primers 8f and P2 covering the V1-V3 regions of the bacterial 16S rRNA gene ( Table 2). The primers used for the amplicon libraries were equipped with adapters for the 454 FLX platform, and each forward primer contained unique 6-nucleotide long barcode sequence as described by Bomberg et al [50]. The archaeal and bacterial amplicon library PCR was performed as described in Table S1.…”

Wells provide a distorted view of life in the aquifer: implications for sampling, monitoring and assessment of groundwater ecosystems

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Microbial co-occurrence patterns in deep Precambrian bedrock fracture fluids

“…While the microbial communities in deep marine subsurface environments have been intensively characterized within the last decade with next-generation sequencing methods Biddle et al, 2008Biddle et al, , 2011Brazelton et al, 2012), high-throughput (HTP) sequencing techniques have only recently emerged in characterization of the terrestrial deep subsurface microbial communities Bomberg et al, 2014Bomberg et al, , 2015aLau et al, 2014;Mu et al, 2014). A vast amount of data obtained from HTP sequencing studies can be used to estimate ecological measures such as species richness, abundance and β-diversity, but it also allows the exploration of significant relationships between microbial taxa and their coexistence in a specific environment (Zhou et al, 2011;Barberan et al, 2012;Lupatini et al, 2014).…”