UPSC Prelims 2023 Question:

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?

Explanation:

• "Thermophiles" are microorganisms with optimal growth temperatures between 60 and 108 degrees Celsius. They are isolated from a number of marine and terrestrial geothermally-heated habitats including shallow terrestrial hot springs, hydrothermal vent systems, sediment from volcanic islands, and deep-sea hydrothermal vents. The boiling point of water is 100 degrees Celsius. So, statement 1 is correct.
  
  

• The microorganisms live in every part of the biosphere, and some of them are even capable of growing at low temperatures, including those below the freezing point. These microorganisms live in the sea or in high mountains, but unfortunately also in refrigerators, where they may spoil or, as pathogens contaminate foods. So, statement 2 is correct.
  
  

• Microorganisms that grow optimally at pH less than 5.55 are called acidophiles. For example, the sulfur-oxidizing Sulfolobus spp. isolated from sulfur mud fields and hot springs in Yellowstone National Park are extreme acidophiles. These archaea survive at pH values of 2.5–3.5. So, statement 3 is correct.
  
  

Therefore, option (3) is the correct answer.

Subject: Environment | Biodiversity and Conservation