Geomicrobiology is the scientific field at the intersection of geology and microbiology. The field of geomicrobiology concerns the role of microbe and microbial processes in geological and geochemical processes and vice versa. The field is especially important when dealing with microorganisms in aquifers and public drinking water supplies.
Microorganisms are known to affect 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.
Another area of investigation in geomicrobiology is the study of extremophile organisms, the microorganisms that thrive in environments normally considered hostile to life. Such environments may include extremely hot (hot springs or mid-ocean ridge black smoker) environments, extremely saline environments, or even space environments such as Martian soil or comets.
Recent observations and research in hyper-saline lagoon environments in Brazil and Australia have shown that anaerobic sulfate-reducing bacteria may be directly involved in the formation of dolomite. This suggests the alteration and replacement of limestone sediments by dolomitization in ancient rocks was possibly aided by ancestors to these anaerobic bacteria.
Microbes are being studied and used to degrade organic and even nuclear waste pollution (see Deinococcus radiodurans) and assist in environmental cleanup. An application of geomicrobiology is bioleaching, the use of microbes to extract metals from mine waste.
Microbially precipitated minerals
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. Certain iron, uranium and even gold ores are thought to have formed as the result of microbe action.
Microbial degradation of hydrocarbons
Microbes can affect the quality of oil and gas deposits through their metabolic processes. Microbes can influence the development of hydrocarbons by being present at the time of deposition of the source sediments or by dispersing through the rock column to colonize reservoir or source lithologies after the generation of hydrocarbons.
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