CUET-PG — Environmental Sciences · India · National Testing Agency
Original practice questions written to the published syllabus · not past papersMicroorganisms as the engines of nutrient cycling, wastewater treatment, bioremediation and disease. GATE ES Section 3 examines it from cell structure to Monod kinetics and coliform counts.
In the exams: GATE ES Section 3; UGC NET Environmental Sciences Unit 3; ICAR AICE subject 71 Units 4–5 (bioremediation, composting)
ICAR AIEEA-PG and CUET-PG
Soil microorganisms, nitrogen-fixing and phosphate-solubilising organisms, biofertilisers, decomposition and C:N ratio, and basic water microbiology.
How our questions for CUET-PG spread across the units of Environmental Microbiology. Difficulty: 17 easy, 16 medium, 0 hard.
| Prokaryotic and eukaryotic microorganisms; classification and diversity | 5 | |
| Cell structure: membranes, walls, endospores, organelles | 4 | |
| Enzymes and enzyme kinetics | 4 | |
| Fermentation and anaerobic respiration | 3 | |
| Bacterial growth: specific growth rate, doubling time, Monod model | 3 | |
| Cell chemistry: proteins, nucleic acids, lipids, polysaccharides | 2 | |
| Microbial metabolism: glycolysis, TCA cycle, electron transport | 2 | |
| Control of microorganisms: physical and chemical methods | 2 | |
| Plant-microbe and soil-microbe interactions | 2 | |
| Microorganisms in biogeochemical cycling | 2 | |
| Pathogens, transmission routes and indicator organisms | 2 | |
| Batch and continuous culture | 1 | |
| Microorganisms in wastewater treatment and bioremediation | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Why do Gram-negative bacteria appear pink after Gram staining?
C. Thin walls lose crystal violet and take up safranin
Alcohol decolourises thin-walled Gram-negative cells, which then take the pink counterstain; Gram-positive cells retain purple.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
A microorganism with an optimum growth temperature of about 60 °C is a
A. thermophile
Thermophiles grow best above about 45 °C; psychrophiles below about 15 °C; mesophiles about 20–45 °C; halophiles are defined by salt.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
Which macromolecule makes up the largest share of a bacterial cell's dry weight?
C. Protein
Protein is roughly half the dry weight; RNA exceeds DNA, and lipids and polysaccharides are smaller fractions.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
Prokaryotic ribosomes are
A. 70S
Prokaryotes have 70S ribosomes; eukaryotic cytoplasmic ribosomes are 80S.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
What is the correct sequence of stages in anaerobic digestion?
C. Hydrolysis, acidogenesis, acetogenesis, methanogenesis
Polymers are hydrolysed, fermented to acids, converted to acetate and H2, then to methane.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
Which organism carries out alcoholic fermentation used in brewing and bioethanol production?
D. Saccharomyces cerevisiae
The yeast S. cerevisiae ferments sugars to ethanol and CO2.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
In the Monod equation, Ks is
A. the S giving half of μmax
Ks is the half-saturation constant, analogous to Km.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
What are the standard autoclave conditions for sterilisation?
C. 121 °C at 15 psi for 15 minutes or more
Pressurised steam at 121 °C kills endospores; 63 °C/30 min and 72 °C/15 s are pasteurisation.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
Nitrification inhibitors such as dicyandiamide and nitrapyrin act by slowing
B. the oxidation of ammonium to nitrite
They inhibit ammonia monooxygenase, keeping nitrogen as ammonium and reducing nitrate leaching and N2O.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
Who developed the activated sludge process in 1914?
D. Edward Ardern and William Lockett
Ardern and Lockett developed activated sludge in Manchester; Lettinga developed UASB; Snow studied cholera.
Further reading: See the manual sources: Brock Biology of Microorganisms; Pepper et al.; Rittmann & McCarty; Standard Methods Part 9000; WHO guidelines
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