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Deep Subsurface Biosphere. By Sara Cox. Outline. History Deep Subsurface Biosphere SLiMEs Microbial Organisms TEAPs Anaerobic Degradation of Benzoate Sample-taking and Contamination Future References. History.

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outline
Outline
  • History
  • Deep Subsurface Biosphere
  • SLiMEs
  • Microbial Organisms
  • TEAPs
  • Anaerobic Degradation of Benzoate
  • Sample-taking and Contamination
  • Future
  • References
history
History
  • 1960’s and 1970’s: discovery of microbes in geysers at temperatures of 160°F
  • 1981: Dr Stetter discovers hyperthermophiles in Icelandic hot springs
  • 1989: first routine use of the term deep subsurface biosphere
deep subsurface biosphere4
Deep Subsurface Biosphere
  • Usually considered to begin 50m below surface of the Earth and extend to variable depth
  • Depth determined by maximum temperature
  • Oceanic crust heats at a rate of 15°C per km, and reaches 110°C at about 7 km depth
  • Continental crust heats at 25°C per km and reaches 110 °C at 4 km
  • Deepest samples recovered at 75°C from a depth of 2.8 km
slimes
SLiMEs
  • Subsurface lithoautotrophic microbial ecosystems
  • fluid-filled pores, cracks and interstices of rock and feed off heat and chemicals, main microbial habitat is in hot aquifers under continents and oceanic abyssesIf 1% of total pore space was occupied, the mass of microbes would be 200 trillion tons, enough to coat land surfaces 5 feet thick
microbial organisms
Microbial organisms
  • Hyperthermophilic methanogens at temperatures up to 110°C or 6 km deep
  • Subsurface microbes may be able to withstand temperatures up to 230°F and possibly briefly to 700 °F, result of pressure
  • Most terrestrial microbes die at the boiling point of water
slide7
Bacteria, archaea and eukaryotic microorganisms are all well distributed, with the exceptions of algae and ciliates
  • High clay layers have low microbial numbers but sandy layers have elevated numbers
teaps
TEAPs
  • Terminal electron accepting processes
  • The most common TEAPs are O2, nitrate, Mn (IV), Fe (III), sulfate and CO2
  • Distribution of TEAPs in deep aquifers occur in this order: oxic, nitrate and Mn(IV) reducing, Fe(III) reducing, sulfate reducing and finally methanogenic
anaerobic degradation of benzoate
Anaerobic degradation of benzoate
  • C6H5COO- + 7H20 3CH3COO- + HCO3- + 3H+ + CH2
  • Not thermodynamically favorable unless linked with aceoclastic methanogenesis
  • 4C6H5COO+ + 18H20 15 CH4 +13CO2
  • Anaerobic degradation of phenol is also linked with acetoclastic methanogenesis
sample taking and contanimation
Sample-taking and Contanimation
  • Debate: are subsurface microbes actually indigenous or are they merely surface contaminants?
  • Lack of photosynthetic organisms in samples
  • Specialized drilling and sample-collecting to try to prevent contamination
slide12
Nitrogen or argon gases used in in drilling rather than fluids
  • Sterilized drilling fluid or tracers
  • Sterile and non-oxidizing containment of samples
  • Argon-filled bags enclose all tools and samples kept in boxes of argon or nitrogen
slide14
If non-oxidizing gases are not used in drilling, drilling fluids are often marked with tracers (fluorescent or organically labeled)
  • When samples are taken either completely untagged samples are used or the contaminated layers are removed and the “clean” areas are inspected
future
Future
  • Possible life on other planets? T. Gold predicts at least 10 possible deep biospheres in our solar system
  • Drilling not feasible, collection of samples from deep layers that are now exposed, ex. Valley Marinara on Mars, once several km deep
slide16
Untapped pool of genetic diversity
  • Medical: investigation of microbes for anti-cancer and anti-AIDS drugs
  • Bioaugmentation: pollution-eating bacteria for ground water cleanup
  • Mary deFlaun (Envirogen) non-adhesive bacteria
  • Storage of nuclear waste underground
references
References

Gold, Thomas. 1999. The Deep Hot Biosphere. Copernicus. New York.

Jones, R, Beeman, R. & Suflita, J. 1989. Anaerobic Metabolic Processes in the Deep Terrestrial Subsurface. Geomicrobiology Journal 7 pg. 117-130.

Fredrickson, J. & Onstott, TC. 1996. Microbes Deep Inside the Earth. Scientific American Oct. 1996.

Lovley, D. Chapelle, F. 1995. Deep Subsurface Microbial Processes. Reviews of Geophysics, 33,3.

Reysenbach, A. & Staley, J. ed. 2002. Biodiversity of Microbial Life. Wiley-Liss, Inc. New York.

Sinclair, J. & Ghiorse, W. Distribution of Aerobic Bacteria, Protozoa, Algae, and Fungi in Deep Subsurface Sediments. Geomicrobiology Journal 7. Pg. 15-31.