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Below are proposed edits to the Geomicrobiology page

Sentence to be added to introduction paragraph introducing various topics of study under Geomicrobiology

Geomicrobiologists study microbial interactions within various earth materials such as rocks, minerals, soils, sediment, the atmosphere or the hydrosphere.[1]

Rocks and Minerals[edit]

Microbe-aquifer interactions[edit]

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Microorganisms are known to impact aquifers by modifying their rates of dissolution. In the karstic Edwards Aquifer, microbes colonizing the aquifer surfaces enhance the dissolution rates of the host rock.[2]

In the oceanic crustal aquifer, the largest aquifer on Earth, microbial communities can impact ocean productivity, sea water chemistry as well as geochemical cycling throughout the geosphere. The mineral make-up of the rocks affects the composition and abundance of these subseafloor microbial communities present.[3] Some microbes can aid in decontaminating freshwater resources in aquifers contaminated by waste products (See Bioremediation).

Microbially precipitated minerals[edit]

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Some bacteria use metal ions as their energy source. They convert (or chemically reduce) the dissolved metal ions from one electrical state to another. This reduction releases energy for the bacteria's use, and, as a side product, serves to concentrate the metals into what ultimately become ore deposits. Biohydrometallurgy or in situ mining is where low-grade ores may be attacked by well-studied microbial processes under controlled conditions to extract metals. Certain iron, copper, uranium and even gold ores are thought to have formed as the result of microbe action.[4]

Subsurface environments, like aquifers, are attractive locations when selecting repositories for nuclear waste, carbon dioxide (See carbon sequestration), or as artificial reservoirs for natural gas. Understanding microbial activity within the aquifer is important since it may interact with and impact the stability of the materials within the underground repository.[5] Microbe-mineral interactions contribute to biofouling and microbially induced corrosion. Microbially induced corrosion of materials, such as carbon steel, have serious implications in the safe storage of radioactive waste within repositories and storage containers.[6]

Environmental remediation[edit]

Microbes are being studied and used to degrade organic and nuclear waste pollution (see bioremediation of radioactive waste and Deinococcus radiodurans) and to assist in environmental cleanup.

Acid Mine Drainage[edit]

Main article: Acid mine drainage

Another application of geomicrobiology is bioleaching, the use of microbes to extract metals from mine waste. For example, sulfate-reducing bacteria (SRB) produce H

Soil & Sediment: Microbial remediation[edit]

Main article: Bioremediation

Microbial remediation is used in soils to remove contaminants and pollutants. Microbes play a key role in many biogeochemistry cycles and can effect a variety of soil properties, such as biotransformation of mineral and metal speciation, toxicity, mobility, mineral precipitation, and mineral dissolution. Microbes play a role in the immobilization and detoxification of a variety of elements, such as metals, radionuclides, sulfur and phosphorus, in the soil.Thirteen metals are considered priority pollutants (Sb, As, Be, Cd, Cr, Cu, Pb, Ni, Se, Ag, Tl, Zn, Hg).[7] Soils and sediment act as sinks for metals which originate from both natural sources through rocks and minerals as well as anthropogenic sources through agriculture, industry, mining, waste disposal, among others.

Many heavy metals, such as chromium (Cr), at low concentrations are essential micronutrients in the soil, however they can be toxic at higher concentrations. Heavy metals are added into soils through many anthropogenic sources such industry and/or fertilizers. Heavy metal interaction with microbes can increase or decrease the toxicity. Levels of chromium toxicity, mobility and bioavailability depend on oxidation states of chromium. [8] Two of the most common chromium species are Cr(III) and Cr(VI). Cr(VI) is highly mobile, bioavailable and more toxic to [flora] and [fauna], while Cr(III) is less toxic, more immobile and readily precipitates in soils with [pH] >6. [9] Utilizing microbes to facilitate the transformation of Cr(VI) to Cr(III) is an environmentally friendly, low cost bioremediation technique to help mitigate toxicity in the environment.[10] 2S which precipitates metals as a metal sulfide. This process removed heavy metals from mine waste which is one of the major environmental issues associated with acid mine drainage (along with a low pH).[11]

Another application in geomicrobiology associated with acid mine drainage is bioremediation of contaminated surface water and ground water. Studies have shown that the production of bicarbonate by microbes such as sulfate-reducing bacteria adds alkalinity to neutralize the acidity of the mine drainage waters.[12] Hydrogen ions are consumed while bicarbonate is produced which leads to an increase in pH (decrease in acidity).[13]

Microbial degradation of hydrocarbons[edit]

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Early Earth History and Astrobiology[edit]

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A common field of study withing geomicrobiology is origin of life on earth or other planets. Various rock-water interactions, such as serpentinization and water radiolysis[5], are possible sources of metabolic energy to support chemolithoautotrophic microbial communities on Early Earth and on other planetary bodies such as Mars, Europa and Enceladus.[14] (http://online.liebertpub.com/doi/10.1089/ast.2015.1382)[15]

Interactions between microbes and sediment record some of the earliest evidence of life on earth. Information on the life during Archean Earth is recorded in bacterial fossils and stromatolites preserved in precipitated lithologies such as chert or carbonates.[16][17] Additional evidence of early life on land ca. 3.5 billion years ago can be found in the Dresser formation of Australia in a hot spring facies, indicating that some of Earth's earliest life on land occurred in in hot springs.[18] Microbially induced sedimentary structures (MISS) are are found throughout the geologic record up to 3.2 billion years old. They are formed by the interaction of microbial mats and physical sediment dynamics, and record paleoenvironmental data as well as providing evidence of early life.[19] The different paleoenvironments of early life on Earth also serves as model when searching for potential fossil life on Mars.

Extremophiles[edit]

Main article: Extremophiles

Observations and research in hyper-saline lagoon environments in Brazil and Australia as well as slightly saline, inland lake environments in NW China have shown that anaerobic sulfate-reducing bacteria may be directly involved in the formation of dolomite.[20]This suggests the alteration and replacement of limestone sediments by dolomitization in ancient rocks was possibly aided by ancestors to these anaerobic bacteria.[21]

See also[edit]

References[edit]

  1. ^ U.S. Geological Survey (2007). "Facing tomorrow's challenges - U.S. Geological Survey science in the decade 2007-2017". U.S. Geological Survey Circular. 1309: 58.
  2. ^ Gray, C.J.; Engel, A.S. (2013). "Microbial diversity and impact on carbonate geochemistry across a changing geochemical gradient in a karst aquifer". The ISME Journal. 7: 325–337.
  3. ^ Smith, A.R.; Fisk, M.R.; Thurber, A.R; Flores, G.E.; Mason, O.U.; Popa, R.; Colwell, F.S. (2016). "Deep crustal communities of the Juan de Fuca ridge are governed by mineralogy". Geomicrobiology. 34 (2): 147-156. doi:10.1080/01490451.2016.1155001.
  4. ^ Rawlings, D.E. (2005). "Characteristics and adaptability of iron- and sulfur-oxidizing microorganisms used for the recovery of metals from minerals and their concentrates". Microbial Cell Fact. 4 (13). doi:10.1186/1475-2859-4-13.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  5. ^ a b Colwell, F.S.; D'Hondt, S. (2013). "Nature and Extent of the Deep Biosphere". Reviews inf Mineralogy and Geochemistry. 75 (1): 547-574.
  6. ^ Rajala, Pauliina; Bomberg, Malin; Vepsalainen, Mikko; Carpen, Leena (2017). "Microbial fouling and corrosion of carbon steel in deep anoxic alkaline groundwater". Biofouling. 33 (2): 195-209.
  7. ^ Gadd, GM (2010). "Metals, minerals and microbes: geomicrobiology and bioremediation". Microbiology. 156: 609-43. doi:10.1099/mic.0.037143-0.
  8. ^ Cheung, K.H.; Gu, Ji-Dong (2007). "Mechanism of hexavalent chromium detoxification by microorganusms and bioremediation application potential: A review". International Biodeterioration & Biodegradation. 59: 8-15. doi:10.1016/j.ibiod.2006.05.002.
  9. ^ Al-Battashi, H; Joshi, S.J.; Pracejus, B; Al-Ansari, A (2016). "The Geomicrobiology of Chromium (VI) Pollution: Microbial Diveristy and its Bioremediation Potential". The open Biotechnology Journal. 10: 379-389. doi:10.2174/1874070701610010379.
  10. ^ Choppola, G; Bolan, N; Park, JH (2013). "Chapter two: Chromium contamination and its risk assessment in complex environmental settings". Advances in Agronomy. 120: 129-172.
  11. ^ Luptakova, A; Kusnierova, M (2005). "Bioremediation of acid mine drainage contaminated by SRB". Hydrometallurgy. 77 (1–2): 97-102.
  12. ^ Kaksonen, A.H.; Puhakka, J.A (2007). "Sulfate Reduction Based Bioprocesses for the Treatment of Acid Mine Drainage and the Recovery of Metals". Engineering in Life Sciences. 7 (6): 541-564. doi:10.1002/elsc.200720216.
  13. ^ Canfield, D.E (2001). "Biogeochemistry of Sulfur Isotopes". Reviews in Mineralogy and Geochemistry. 43 (1): 607-636.
  14. ^ McCollom, Thomas M.; Christopher, Donaldson (2016). "Generation of hydrogen and methane during experimental low-temperature reaction of ultramafic rocks with water". Astrobiology. 16 (6): 389-406.
  15. ^ Onstott, T.C.; McGown, D.; Kessler, J.; Sherwood Lollar, B.; Lehmann, K.K.; Clifford, S.M. (2006). "Martian CH4: Sources, Flux, and Detection". Astrobiology. 6 (2): 377-395.
  16. ^ Noffke, Nora (2007). "Microbially induced sedimentary structures in Archean sandstones: A new window into early life". Gondwana Research. 11 (3): 336-342. doi:10.1016/j.gr.2006.10.004.
  17. ^ Bontognali, T. R. R.; Sessions, A. L.; Allwood, A. C.; Fischer, W. W.; Grotzinger, J. P.; Summons, R. E.; Eiler, J. M. "Sulfur isotopes of organic matter preserved in 3.45-billion-year-old stromatolies reveal microbial metabolism". PNAS. 109 (38). doi:10.1073/pnas.1207491109.
  18. ^ Djokic, Tara; Van Kranendonk, Martin J.; Campbell, Kathleen A.; Walter, Malcolm R.; Ward, Colin R. (2017). "Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits". Nature Communications. 8. doi:10.1038/ncomms15263.
  19. ^ Noffke, Nora; Christian, Daniel; Wacey, David; Hazen, Robert M. (2013). "Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia". Astrobiology. 13 (12): 1103-1124.
  20. ^ Deng, S; Dong, H; Hongchen, J; Bingsong, Y; Bishop, M (2010). "Microbial dolomite precipitation using sulfate reducing and halophilic bacteria: results from Quighai Lake, Tibetan Plateau, NW China". Chemical Geology. 278: 151-159. doi:10.1016/j.chemgeo.2010.09.008.
  21. ^ Dillon, Jesse (2011). "The Role of Sulfate Reduction in Stromatolites and Microbial Mats: Ancient and Modern Perspectives". Stromatolites: Interaction of Microbes with Sediments: 571-590. doi:10.1007/978-94-007-0397-1_25.
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