Consider the following statements : 1. Some microorganisms can grow in environments with temperature above the boiling point of water. 2. Some microorganisms can grow in environments with temperature below the freezing point of water. 3. Some microorganisms can grow in highly acidic environment with a pH below 3. How many of the above statements are correct?
- (a) Only one
- (b) Only two
- (c) All three ✓ UPSC's answer
- (d) None
Why the answer is (c)
• Extremophiles are microorganisms adapted to conditions lethal to most life.
• Hyperthermophiles such as Methanopyrus kandleri grow at 100–122 °C in deep-sea hydrothermal vents, where pressure keeps water liquid above its normal boiling point — statement 1 is correct.
• Psychrophiles grow in Antarctic brine channels and permafrost at −10 °C to −20 °C, using antifreeze proteins — statement 2 is correct.
• Acidophiles such as Picrophilus and Acidithiobacillus thrive at pH 0–3 in acid mine drainage and hot springs — statement 3 is correct.
• Hence all three, option (c). Extremophiles are important for astrobiology and industrial enzymes (e.g. Taq polymerase for PCR).
Why the other options are wrong
- (a) Only one
- All three extremes are inhabited by microorganisms.
- (b) Only two
- Hyperthermophiles, psychrophiles and acidophiles all exist, making three.
- (d) None
- Extremophiles exist for all three conditions.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2023, held on 28 May 2023. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.