Abundance and Diversity of Biofilms in Natural and Artificial Aquifers of the Äspö Hard Rock Laboratory, Sweden
Journal article, 2011
Six cores were drilled and retrieved from 186-m
12 depth in the Äspö Hard Rock Laboratory (HRL) tunnel to
13 investigate whether indigenous biofilms develop on fracture
14 surfaces in groundwater-conducting aquifers in granitic
15 rock. A clone library was constructed from fracture surface
16 material (FSM), for community composition analysis.
17 Quantitative polymerase chain reaction (qPCR) was applied
Q1 18 to quantify gene copies using the 16S rRNA gene for
19 domain Bacteria and the adenosine-phosphosulfate reduc-
Q1 20 tase gene (apsA) for sulfate-reducing bacteria (SRB).
21 Results were compared with three groundwater systems
22 with biofilms in laminar flow reactors (LFRs) at 450-m
23 depth in the Äspö HRL. The total number of cells, counted
24 microscopically, was approximately 2×105 cells·cm–2 in the
25 LFR systems, consistent with the obtained qPCR 16S rRNA
26 gene copies. qPCR analysis reported ∼1×102 up to ∼1×104
27 gene copies·cm–2 on the FSM from the drill cores. In the
28 FSM biofilms, 33% of the sequenced clones were related to
29 the iron-reducing bacterium Stenotrophomonas maltophilia,
30 while in the LFR biofilms, 41% of the sequenced clones
31 were affiliated with the genera Desulfovibrio, Desulforho-
32 palus, Desulfomicrobium, and Desulfobulbus. The commu-
33 nity composition of the FSM biofilms differed from the
drill water community, excluding drill water contamination. 34
This work reports significant numbers of microorganisms 35
on natural hard rock aquifer fracture surfaces with site- 36
specific community compositions. The probability that 37
biofilms are generally present in groundwater-conducting 38
aquifers in deep granitic rock is consequently great.
sulfate-reducing bacteria
biomass
subsurface microbiology
apsA
16S rRNA
biofilm