What we know so far…

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A bacterial biofilm growing on nutrient rich fracture water 1.3 km below the surface in Beatrix Gold Mine, South Africa. NOTE: This image does not represent the bacterial communities I sample.

In order to study life kilometers below the earth’s surface, subterraneauts travel underground through deep mine shafts around the globe.  These scientists collect and analyze fracture waters that have been locked away for thousands of years — completely removed from the sun.  The deepest and most well-studied mines are located in South Africa.  Scientists that study these deep sites use  a “prawn” or similar device (see below) attached to a borehole to sample water that hides meters beyond the mine’s walls.

One of the most recognized discoveries of deep subsurface research is the unprecedented identification of “an ecosystem of one”.  Here, scientists performed a metagenomic study on a 2.8 km deep fracture water community and found that a novel bacterium, Candidatus Desulforudis audaxviator,  accounted for >99.9% of the microbial community (Chivian et al., 2008).  In order to survive on its own, the genome of D. audaxviator  reveals that it is capable of deriving energy via radiolytically derived chemical species and fixing both nitrogen and carbon. 

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A “prawn” attached to a subsurface borehole providing a sterile way to sample and study deep subsurface water and bacterial communities

Since the publication of Chivian et al. 2008, no other borehole has exhibited such an overwhelming dominance of a single species.  16S rRNA amplification across several deep subsurface locations indicate that the majority of the deep terrestrial biosphere consists of low-diversity populations dominated by Firmicutes and  Proteobacteria [1,2,3].

Aside from bacteria, the deep subsurface has been found to be home to archaea and, with the discovery of a deep subsurface nematode by Borgonie et al. 2011, eukaryotes.

Today, deep subsurface biology is being revolutionized through the introduction and widespread use of high-throughput sequencing.  Keep an eye on this blog to learn more about these bioinformatic techniques!!!!!

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