Nutrient Agar: Principle, Composition, Preparation and Uses

I use nutrient agar every day in my laboratory; it is one of the most important culture media in medical bacteriology. In this article, I will discuss its composition, uses, limitations, and how to prepare it.


◉ What is Nutrient Agar?

◉ Composition of nutrient agar

◈ The composition of nutrient agar can be adjusted to obtain optimal performance:



◉ Preparation of nutrient agar


Note : Nutrient agar with 0.8% NaCl and pH 6.0 is used for the culture of bacteria requiring slightly acidic conditions. Nutrient media can be used as enriched media by the addition of 10% blood or other biological fluids such as ascetic fluid, serum, etc.


◉ What is nutrient agar used for?

Nutrient agar provides essential nutrients required for the growth of bacteria, yeast, and molds. Here are some of the primary uses of nutrient agar:

◉ What bacteria grow on nutrient agar?

Nutrient agar contains a balanced mixture of nutrients and lacks selective components, allowing the growth of a wide variety of bacteria, yeast, and molds. Here are some examples of bacteria that commonly grow on nutrient agar:

Fastidious bacteria, including species like Haemophilus and certain Streptococcus strains, have specific nutritional requirements that may not be met by the general-purpose nutrient agar alone. They typically require enriched media that provide additional nutrients and growth factors to support their growth.

◉ What is the difference between Nutrient Agar and Nutrient Broth?

Nutrient agar and nutrient broth share almost the same media composition. The main difference between them lies in the fact that:

  1. Nutrient agar (solid medium) contains a solidifying agent, agar powder, causing the medium to solidify at room temperature. In contrast, nutrient broth (liquid medium) does not include agar, remaining in a liquid state.
  2. Bacterial growth in nutrient agar results in the formation of colonies, while in nutrient broth, the broth becomes more turbid.

◉ Pictures

◈ Some colonies may exhibit characteristic pigmentation:


◉ Conclusion

In conclusion, nutrient agar stands out as a versatile and widely used medium in microbiology, facilitating the growth of a diverse range of bacteria, making it highly suitable for routine laboratory work. However, it's essential to note that while nutrient agar is effective for many bacteria, it may not support the growth of extremely fastidious organisms with specific nutritional requirements.


  • Author: Dr. Belouahad Loqman
  • Microbiologist Doctor in Ibn Zohr hospital - Algeria
  • Updated: February 2024
  • References

    1. Difco™ & BBL™ Manual, 2nd Edition
    2. BBL Nutrient agar- 2006
    3. thermofisher : nutrient agar
    4. oxoide : NUTRIENT AGAR
    5. merck millipore : Nutrient Agar pH 6.0 with 0.8% NaCl
    6. thermofisher : Nutrient Agar