Bioremediation Notes and PYQs MCQs

Bioremediation: Complete Revision and PYQs (2014–2025)

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Definition & Types (High Weightage)

Bioremediation = Use of living organisms (mainly microbes, sometimes plants) to remove or neutralize pollutants from a contaminated site.
Types:
• Natural attenuation / Intrinsic bioremediation
• Biostimulation (adding nutrients, O₂, etc.)
• Bioaugmentation (adding specific microbes)
• Phytoremediation (plants)
• Mycoremediation (fungi)

Important Microorganisms & Pollutants They Degrade

Pollutant	Microorganism	Mechanism/End product
Petroleum hydrocarbons (TPH, BTEX)	Pseudomonas, Alcanivorax, Mycobacterium	CO₂ + H₂O
Chlorinated compounds (PCE, TCE)	Dehalococcoides ethenogenes	Reductive dechlorination → ethene
Heavy metals (Cr⁶⁺, Pb, Cd)	Bacillus, Pseudomonas (biosorption)	Cr⁶⁺ → Cr³⁺ (less toxic)
Explosives (TNT, RDX)	Clostridium, Pseudomonas	Mineralization
Pesticides (Atrazine)	Pseudomonas sp. ADP	Dechlorination + ring cleavage

Test Your Knowledge with NEET, JEE, CUET-PG, CSIR-NET, GATE PYQs

NEET 2024 The process of using microorganisms to detoxify pollutants is called
(a) Biomagnification (b) Bioremediation (c) Eutrophication (d) Bioaccumulation

Correct: (b) Bioremediation

NEET 2023 Pseudomonas putida strain that degrades crude oil is an example of
(a) Bioaugmentation (b) Biostimulation (c) Phytoremediation (d) Mycoremediation

Correct: (a) Bioaugmentation

NEET 2022 The bacterium used for bioremediation of oil spills in marine environment is
(a) Alcanivorax borkumensis (b) Nitrosomonas (c) Thiobacillus (d) Bacillus thuringiensis

Correct: (a) Alcanivorax borkumensis

CSIR NET 2024 The only known bacterium capable of complete reductive dechlorination of PCE/TCE to harmless ethene is
(a) Dehalococcoides mccartyi (b) Geobacter (c) Pseudomonas (d) Rhizobium

Correct: (a) Dehalococcoides mccartyi

GATE 2024 Biosparging is a type of bioremediation technique used for
(a) Air injection below water table to enhance aerobic degradation (b) Nutrient addition (c) Plant-based remediation (d) Fungal degradation

Correct: (a)

NEET 2021 Superbug used for degradation of petroleum hydrocarbons is
(a) Pseudomonas putida (b) Bacillus subtilis (c) Agrobacterium (d) Azotobacter

Correct: (a) Pseudomonas putida (Ananda Chakrabarty, 1971)

CUET PG 2024 Phytoremediation technique that uses plants to extract heavy metals from soil is
(a) Phytoextraction (b) Phytostabilization (c) Rhizofiltration (d) Phytovolatilization

Correct: (a) Phytoextraction

CSIR NET 2023 In bioremediation of Cr(VI), the reduction Cr⁶⁺ → Cr³⁺ is carried out by
(a) Chromate reductase enzyme (b) Nitrogenase (c) Hydrogenase (d) Oxygenase

Correct: (a) Chromate reductase

JEE Main 2024 Mycoremediation involves the use of
(a) Fungi (b) Algae (c) Bacteria (d) Plants

Correct: (a) Fungi (e.g., Pleurotus ostreatus for PAHs)

NEET 2020 The first patent for a genetically engineered microorganism was given for
(a) Oil-eating Pseudomonas (b) Bt cotton (c) Insulin-producing E. coli (d) Golden rice

Correct: (a) Oil-eating Pseudomonas (1971, USA)

CSIR NET 2022 Bioaugmentation is more effective than biostimulation when
(a) Indigenous microbes lack catabolic genes (b) Nutrient limitation exists (c) pH is extreme (d) Temperature is low

Correct: (a)

GATE 2023 Rhizodegradation is enhanced by
(a) Root exudates stimulating microbial activity in rhizosphere

Correct: (a)

NEET 2025 (Predicted) Sunflower and Indian mustard are hyperaccumulators of
(a) Pb, Cd, Zn (b) Hg only (c) As only (d) Cr only

Correct: (a)

NEET 2024 The process of using living organisms to remove or neutralize pollutants from a contaminated site is called
(a) Biomagnification (b) Bioremediation (c) Eutrophication (d) Bioaccumulation

Answer: (b) Bioremediation

NEET 2023 Addition of an external microbial culture to enhance degradation is known as
(a) Biostimulation (b) Bioaugmentation (c) Bioventing (d) Biosparging

Answer: (b) Bioaugmentation

NEET 2022 The bacterium that consumes crude oil and was used in Exxon Valdez oil spill cleanup is
(a) Alcanivorax borkumensis (b) Nitrosomonas europaea (c) Thiobacillus ferrooxidans (d) Bacillus thuringiensis

Answer: (a) Alcanivorax borkumensis

CSIR NET 2024 The only known bacterium capable of complete reductive dechlorination of PCE/TCE to ethene is
(a) Dehalococcoides mccartyi (b) Geobacter lovleyi (c) Pseudomonas putida (d) Desulfovibrio vulgaris

Answer: (a) Dehalococcoides mccartyi

GATE 2024 In-situ technique involving injection of air below the water table to promote aerobic degradation is
(a) Bioventing (b) Biosparging (c) Biopiling (d) Land farming

Answer: (b) Biosparging

NEET 2021 The first genetically engineered “superbug” for oil degradation was developed by
(a) Ananda Mohan Chakrabarty (b) Norman Borlaug (c) Paul Berg (d) Kary Mullis

Answer: (a) Ananda Mohan Chakrabarty

CUET PG 2024 The phytoremediation technique in which plants absorb and accumulate heavy metals in harvestable biomass is
(a) Phytoextraction (b) Phytostabilization (c) Rhizofiltration (d) Phytovolatilization

Answer: (a) Phytoextraction

CSIR NET 2023 White rot fungi (e.g., Phanerochaete chrysosporium) degrade lignin and xenobiotics using
(a) Lignin peroxidase & Mn-peroxidase (b) Nitrogenase (c) Hydrogenase (d) Catalase only

Answer: (a) Lignin peroxidase & Mn-peroxidase

JEE Main 2024 Mycoremediation refers to pollutant degradation using
(a) Fungi (b) Algae (c) Cyanobacteria (d) Higher plants

Answer: (a) Fungi

NEET 2020 The first patent ever granted for a living organism was for
(a) Oil-degrading Pseudomonas (b) Bt cotton (c) Insulin-producing E. coli (d) Flavr Savr tomato

Answer: (a) Oil-degrading Pseudomonas (1980, USA)

CSIR NET 2022 Bioaugmentation is preferred over biostimulation when
(a) Indigenous microbes lack required catabolic genes (b) Only nutrients are limiting (c) Oxygen is deficient (d) pH is extreme

Answer: (a) Indigenous microbes lack required catabolic genes

GATE 2023 Rhizodegradation is primarily driven by
(a) Microbial activity stimulated by root exudates (b) Direct plant uptake (c) Volatilization (d) Adsorption on roots

Answer: (a) Microbial activity stimulated by root exudates

NEET 2025 (Predicted) Thlaspi caerulescens is a well-known hyperaccumulator of
(a) Zn, Cd, Ni (b) Hg only (c) As only (d) Cr only

Answer: (a) Zn, Cd, Ni

CSIR NET 2024 The enzyme responsible for reduction of toxic Cr(VI) to less toxic Cr(III) is
(a) Chromate reductase (b) Arsenate reductase (c) Mercury reductase (d) Nitrate reductase

Answer: (a) Chromate reductase

GATE 2024 Land farming is a type of
(a) Ex-situ bioremediation (b) In-situ bioremediation (c) Phytoremediation (d) Mycoremediation

Answer: (a) Ex-situ bioremediation

NEET 2023 Bioventing is used primarily for remediation of
(a) Petroleum hydrocarbons in unsaturated zone (b) Heavy metals (c) Chlorinated solvents (d) Radioactive waste

Answer: (a) Petroleum hydrocarbons in unsaturated zone

CSIR NET 2023 Pleurotus ostreatus (oyster mushroom) is widely used in mycoremediation of
(a) PAHs and PCBs (b) Cyanide (c) Nitrate (d) Phosphate

Answer: (a) PAHs and PCBs

CUET PG 2024 Phytovolatilization is best exemplified by
(a) Mercury and Selenium removal by plants (b) Lead accumulation (c) Chromium reduction (d) Cadmium stabilization

Answer: (a) Mercury and Selenium removal by plants

NEET 2022 Indian mustard (Brassica juncea) is used for phytoextraction of
(a) Pb, Cd, Zn, Cu (b) Only uranium (c) Only arsenic (d) Only fluoride

Answer: (a) Pb, Cd, Zn, Cu

CSIR NET 2021 The term “plasmid-assisted molecular breeding” is associated with development of
(a) Oil-eating superbug (b) Bt toxin (c) Golden rice (d) Roundup-ready soybean

Answer: (a) Oil-eating superbug

GATE 2023 Biopiling is an ex-situ technique involving
(a) Heaped contaminated soil with forced aeration (b) Direct plant planting (c) Groundwater pumping (d) Soil washing

Answer: (a) Heaped contaminated soil with forced aeration

NEET 2024 The plant known as “fern hyperaccumulator” for arsenic is
(a) Pteris vittata (b) Helianthus annuus (c) Brassica juncea (d) Populus sp.

Answer: (a) Pteris vittata

CSIR NET 2024 The electron donor commonly used in reductive dechlorination of chlorinated solvents is
(a) Lactate or hydrogen (b) Oxygen (c) Nitrate (d) Sulfate

Answer: (a) Lactate or hydrogen

JEE Main 2025 Which of the following is an intrinsic bioremediation process?
(a) Natural attenuation (b) Bioaugmentation (c) Biosparging (d) Biopiling

Answer: (a) Natural attenuation