The agar in nutrient agar microbiological growth medium serves as 0 A solidifying agent 0 B. protein source 0 c medium supplement 4 0D. carbohydrate source
The Correct Answer and Explanation is:
The correct answer is A. Solidifying agent.
Agar is a complex carbohydrate extracted from red algae (specifically, Gelidium or Gracilaria species). It is used in microbiology primarily as a solidifying agent in nutrient agar and other growth media.
Explanation:
- Solidifying agent: The primary role of agar in nutrient agar is to solidify the medium, providing a stable surface for microbial growth. Agar itself is a gelatinous substance that melts at around 85°C and solidifies when cooled to approximately 32–40°C. This property makes it ideal for creating a solid surface for growing microorganisms in Petri dishes, enabling easier observation and isolation of colonies.
- Not a protein source: Agar does not serve as a protein source in nutrient agar. Nutrient agar is typically supplemented with proteins, such as peptones or tryptones, which provide the nitrogen and amino acids necessary for the growth of bacteria. Agar itself is not a protein but rather a polysaccharide.
- Not a medium supplement: While agar is crucial in the preparation of nutrient agar, it is not a supplement like vitamins, minerals, or additional nutrients. It mainly provides the structural base, allowing microorganisms to grow.
- Not a carbohydrate source: Although agar is a carbohydrate, it is not a significant energy source for bacteria growing on nutrient agar. Most bacteria derive their nutrients from the peptones and other organic compounds present in the medium, not from the agar itself.
In summary, agar’s role in microbiological media is to provide a solid surface, making it an essential component in the growth of microorganisms in laboratory settings.
