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UPSC Prelims 2023 · Environment · Species Watch
Consider the following statements: How many of the above statements are correct?
- Some microorganisms can grow in environments with temperature above the boiling point of water.
- Some microorganisms can grow in environments with temperature below the freezing point of water.
- Some microorganisms can grow in highly acidic environment with a pH below 3.
- (a) Only one
- (b) Only two
- (c) All three
- (d) None
Show the answer and explanation
Answer: (c) All three
Microbes survive and grow in all three extremes.
Statement by statement
1. ✓ CORRECT Hyperthermophiles live at vents above 100 °C (water stays liquid under pressure); the record is ~122 °C.
2. ✓ CORRECT Psychrophiles grow below 0 °C in salty water and sea ice.
3. ✓ CORRECT Acidophiles (e.g. Picrophilus) grow at pH below 1.
The idea
Microbes that live in conditions that would kill most life are called extremophiles. Many of them belong to the archaea, an ancient group of single-celled organisms. Their proteins are built to keep working in heat, cold, acid or salt.
Thermophiles: hot springs and deep-sea vents → Psychrophiles: polar ice and deep cold sea → Acidophiles: acid mine water and volcanic springs → Halophiles: salt lakes and salt pans
The trap
“Above boiling point” sounds impossible, but under high pressure water stays liquid above 100 °C.
Elimination technique
All three statements are soft “some microorganisms can…” claims. Plain claims of this kind are usually true in Environment PYQs, which points to all three.
Also know
They are useful. The enzyme used in the PCR test, which copies DNA at high temperature, comes from a bacterium of hot springs. They also guide the search for life on other planets.
🔒 Extremophiles: thermophiles (heat), psychrophiles (cold), acidophiles (acid), halophiles (salt).