Microbes and the Geological Environment
Science & Technology › Biotechnology – Applications · Topic 11.17
Geomicrobiology studies how microbes shape and are shaped by rocks, minerals, water and sediments, and it shows that microbes have changed the Earth for billions of years. Bacteria and archaea can dissolve or form minerals, make iron and sulphur compounds, produce methane, and live kilometres below the surface in the deep biosphere. Cyanobacteria built stromatolites and released the oxygen that changed the atmosphere about 2.4 billion years ago. Applications include bioleaching of metals from low grade ore using Acidithiobacillus ferrooxidans, microbially enhanced oil recovery, biocementation of soil, and clean up of mine waste. Microbes can also damage structures through biocorrosion.
5 min read · UPSC Prelims · Science & Technology · Biotechnology – Applications
At a Glance
- Field Geomicrobiology
- Metal recovery Bioleaching
- Ancient evidence Stromatolites
- Oxygen event About 2.4 billion years ago
- Damage Biocorrosion
- Exam link UPSC Prelims, Science & Technology: Biotechnology – Applications
Where Does It Fit?
This topic follows landfilling and pollution monitoring. It widens the lens from waste to the interaction of microbes with rocks and minerals, which has uses in mining and construction. Previous topic: Landfilling Technologies and Detection/Monitoring of Pollutants. Next topic: Forest Biotechnology.
What Roles Do Microbes Play in Rocks, Minerals and Water?
| Process | Microbial role |
|---|---|
| Stromatolites | Layered structures built by cyanobacteria in shallow water. Some are 3.5 billion years old and show early life |
| Great Oxidation Event | Cyanobacteria released oxygen, which rose in the air about 2.4 billion years ago and changed life and rocks |
| Banded iron formations | Iron rich rocks formed when oxygen from microbes reacted with dissolved iron, a main source of iron ore |
| Weathering of rocks | Microbes and lichens dissolve minerals by making acids, helping soil formation |
| Carbonate precipitation | Some bacteria help to form limestone, and some are used to bind soil |
| Sulphur and iron cycles | Sulphate reducing bacteria make hydrogen sulphide, and iron oxidising bacteria cause acid drainage in mines |
| Methane production | Archaea called methanogens make methane in wetlands, rumen and sediments |
What Are the Uses and Risks?
- Bioleaching: bacteria such as Acidithiobacillus ferrooxidans oxidise sulphide minerals and release copper, gold or uranium into solution, useful for low grade ore
- Biooxidation of gold ore: microbes open up the sulphide in which gold is locked
- Microbially enhanced oil recovery: microbes or their products release trapped oil
- Biocementation: bacteria such as Sporosarcina pasteurii make calcite that binds sand into a solid, a possible green alternative to cement
- Self healing concrete: bacteria spores in concrete form limestone to seal cracks
- Acid mine drainage: microbes make mine water acidic, which is a major pollution problem, and can also help to treat it
- Biocorrosion: sulphate reducing bacteria corrode pipelines and ships
- Bioremediation of mine waste: microbes and plants stabilise tailings and take up metals, as in Bioremediation and Microbial Remediation
What Else Should You Remember?
- Deep biosphere: microbes have been found kilometres below ground and the sea floor, living on rock chemistry and extremely slowly
- Extremophiles: thermophiles, acidophiles and halophiles live in hot springs, acid water and salt lakes, and their enzymes are used in industry
- Mars and astrobiology: studies of microbes in rocks guide the search for life on other planets
- Hydrothermal vents: ocean floor vents support life that uses chemicals, not sunlight, for energy
- Biomineralisation: living things make minerals, such as shells of corals, and magnetite in magnetotactic bacteria
- Magnetotactic bacteria: bacteria with magnetic crystals that align with the Earth’s magnetic field
- Indian context: India has low grade copper and other ores, so bioleaching has been tested in research and pilots. Check the current status before quoting
- Link with mining policy: mining affects forests and rivers, so biological methods that cut energy use and waste are of interest
- Carbon storage: microbes help to turn carbon dioxide into carbonate minerals underground, which links to carbon capture ideas
- Gas hydrates: microbes produce methane that is trapped in ice like hydrates in sea sediments, including off the Indian coast
- Safety: bioleaching needs control of acid and metal release to avoid pollution
- Link: communities of microbes are studied by metagenomics, as in Industrial Genetics and Microbial Ecology
- Biofilms in rocks: microbes living as films on mineral surfaces speed up dissolution of rock and play a part in soil formation
- Nitrogen and carbon cycles: geological stores such as limestone and fossil fuels are linked to microbial cycles of carbon, and these are covered in nutrient cycling topics of the environment subject
- Microbial mats: layered communities in salt flats and hot springs are modern versions of ancient stromatolites
- Uranium and metals: microbes can change the solubility of metals such as uranium and chromium, which is used in cleaning contaminated groundwater
Why Does It Matter for the Exam?
- Terms: stromatolite, bioleaching, biocorrosion
- Organisms: Acidithiobacillus, Sporosarcina, methanogens
- Earth history: Great Oxidation Event
- Current affairs link: green mining and critical minerals
- Common errors: saying that bioleaching uses plants or that stromatolites are animals
As an analytical point, microbes can make mining and construction cleaner, but control of acid and metal release is essential. The same knowledge also supports the search for life beyond Earth.
Why Is This Topic Important?
- Earth history Oxygen and iron
- Uses Bioleaching
- Risks Acid drainage
What Came Next?
The next topic covers biotechnology in forestry. Next topic: Forest Biotechnology.
Key People and Terms
- Stromatolite Layered microbial rock
- Bioleaching Microbial metal recovery
- Methanogen Methane making archaeon
- Acidophile Acid loving microbe
- Biocementation Microbial binding of soil
- Tailings Mine waste
Exam Corner
Points to Remember
- Bioleaching microbe: Acidithiobacillus ferrooxidans.
- Oxygen rise: about 2.4 billion years ago.
- Stromatolites built by cyanobacteria.
- Methanogens are archaea.
- Biocorrosion by sulphate reducing bacteria.
Do Not Confuse With
- Bioleaching and bioremediation Recovering metals versus cleaning pollution
- Stromatolite and fossil Layered microbial structure versus preserved remains
- Bacteria and archaea Two microbial domains
Memory Hook
Microbes made the oxygen, built the iron bands, leach the copper and eat the pipe.
Mains Angle
Questions ask about terms and applications. These points help.
- Role Shaping Earth
- Uses Mining and building
- Risks Acid drainage
A Question You May Face
An original practice question, not a past paper question.
“Discuss the role of microbes in shaping the geological environment and their applications in mining and construction.”
How to Answer
- Role Oxygen, minerals.
- Uses Bioleaching, biocement.
- Risks Acid, corrosion.
- Way Control and research.
GS Relevance
Frequently Asked Questions
What is geomicrobiology?
Geomicrobiology is the study of the interactions between microbes and the geological environment, including rocks, minerals, sediments and water. It explains how microbes weather rocks, form or dissolve minerals, cycle iron and sulphur, and have changed the atmosphere, and it has uses in mining, construction and environmental clean up.
What is bioleaching?
Bioleaching is the use of microbes to extract metals from ore. Bacteria such as Acidithiobacillus ferrooxidans oxidise sulphide minerals, which dissolves metals like copper into solution that can be collected. It is useful for low grade ores that are not worth processing by smelting and uses less energy.
What are stromatolites?
Stromatolites are layered rock structures built by communities of microbes, mainly cyanobacteria, which trap sediment and precipitate minerals. Some fossil stromatolites are about 3.5 billion years old and are among the oldest evidence of life on Earth. Living stromatolites still exist in places such as Shark Bay in Australia.
How did microbes change the Earth's atmosphere?
About 2.4 billion years ago, cyanobacteria that carried out photosynthesis released large amounts of oxygen, an episode called the Great Oxidation Event. The oxygen reacted with dissolved iron to form banded iron formations and slowly built up in the air, which made complex life possible later.
What is biocementation?
Biocementation is a process in which bacteria such as Sporosarcina pasteurii cause the formation of calcium carbonate that binds sand or soil particles together into a solid mass. It is studied as a lower carbon alternative to cement for soil strengthening, erosion control and repair of cracks.
PYQ Practice — Statement Analysis
1 Stromatolites are built by cyanobacteria.
Layered microbial structures.
2 Bioleaching uses plants to extract metals from ore.
It uses bacteria.
3 Methanogens are archaea that produce methane.
In wetlands and rumen.
4 The Great Oxidation Event occurred about 2.4 billion years ago.
Caused by cyanobacteria.
Past Mains Questions on This Topic
This topic comes under Biotechnology – Applications. UPSC Mains questions asked on the matching syllabus topic, year-wise with marks:
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