1 / 17

Deep Subsurface Biosphere

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.

deacon
Download Presentation

Deep Subsurface Biosphere

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Deep Subsurface Biosphere By Sara Cox

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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

More Related