Difference Between Nutrient Agar and Nutrient Broth

Main Difference – Nutrient Agar vs Nutrient Broth

Nutrient agar and nutrient broth are two types of growths used to grow microorganisms. The main difference between nutrient agar and nutrient broth is that nutrient agar is a solid medium whereas nutrient broth is a liquid medium. Agar is added to the nutrient agar in order to solidify the medium. It is a polymer made up of galactose. Nutrient agar is suitable for the cultivation of microorganisms as it allows colony formation. Nutrient broth is suitable for the cultivation of the fastidious microorganisms and for the maintenance of stock cultures. Nutrient agar is prepared in Petri dishes while nutrient broth is prepared in test tubes or bottles.

Key Areas Covered

1. What is Nutrient Agar
     – Definition, Ingredients, Preparation
2. What is Nutrient Broth
     – Definition, Ingredients, Preparation
3. What are the Similarities Between Nutrient Agar and Nutrient Broth
     – Outline of Common Features
4. What is the Difference Between Nutrient Agar and Nutrient Broth
     – Comparison of Key Differences

Key Terms: Agar, Colonies, Liquid Media, Nutrient Agar, Nutrient Broth, Petri Dishes, Solid Media

What is Nutrient Agar

Nutrient agar refers to a general purpose medium that supports the growth of a wide range of non-fastidious organisms. It is a solid medium as 2% agar is used during the preparation. It is an inexpensive medium for the cultivation of microorganisms. Generally, nutrient agar is prepared in Petri dishes. The main function of nutrient agar is to facilitate the colony formation as it is a solid media. Colonies of different types of organisms on nutrient agar are shown in figure 1.

Figure 1: Colonies on Nutrient Agar

Ingredients of Nutrient Agar

Directions to Prepare

1. Suspend 28g nutrient agar powder in 1L.
2. Autoclave at 121 degrees Celsius for 15 min.
3. Mix well and pour into Petri dishes.

What is Nutrient Broth

Nutrient broth refers to a general purpose, liquid medium that allows the growth of fastidious organisms. Generally, a nutrient broth is prepared in test tubes or reagent bottles. The main function of nutrient broth is the maintenance of the stocks of microorganisms. The nutrient broth in bottles is shown in figure 2.

Figure 2: Nutrient Broth

Ingredients of Nutrient Broth  

Direction to Prepare

1. Suspend 25g nutrient broth powder in 1L.
2. Dispense the solution in test tubes or bottles.
3. Autoclave at 121 degrees Celsius for 15 min.

Similarities Between Nutrient Agar and Nutrient Broth

• Nutrient agar and nutrient broth are two types of growth media.
• Both nutrient agar and nutrient broth are general purpose media.
• Both nutrient agar and nutrient broth are inexpensive.
• Both nutrient agar and nutrient broth consist of beef extract and peptones.
• The pH of both nutrient agar and nutrient broth are 7.3.
• Both nutrient agar and nutrient broth are used to cultivate microorganisms.

Difference Between Nutrient Agar and Nutrient Broth

Definition

Nutrient Agar: Nutrient agar refers to a general purpose medium that supports the growth of a wide range of non-fastidious organisms.

Nutrient Broth: Nutrient broth refers to a general purpose, liquid medium that allows the growth of fastidious organisms.

Agar

Nutrient Agar: Nutrient agar consists of 2% of agar.

Nutrient Broth: Nutrient broth does not contain agar.

Composition

Nutrient Agar: Nutrient agar is composed of peptone, beef extract, yeast extract, agar, and sodium chloride.

Nutrient Broth: Nutrient broth is composed of peptone, beef extract, and sodium chloride.

Type of Medium

Nutrient Agar: Nutrient agar is a solid medium.

Nutrient Broth: Nutrient broth is a liquid medium.

Type of Organisms

Nutrient Agar: Nutrient agar is used to grow non-fastidious organisms.

Nutrient Broth: Nutrient broth is used to grow fastidious organisms.

Glassware

Nutrient Agar: Nutrient agar is poured into Petri dishes.

Nutrient Broth: Nutrient broth is poured into test tubes and culture bottles.

Uses

Nutrient Agar: Nutrient agar is used for colony formation of microorganisms.

Nutrient Broth: Nutrient broth is used to maintain stocks of microorganisms.

Conclusion

Nutrient agar and nutrient broth are two types of media used to grow microorganisms. Nutrient agar consists of 2% agar and is a solid media. It is used to obtain colonies of microorganisms. Nutrient broth lacks agar, and it is a liquid medium. It is used to maintain stocks of microorganisms. Therefore, the main difference between nutrient agar and nutrient broth is the texture and purpose of use.

Reference:

1. “Nutrient Agar.” Teknova: Pre-Poured Agar Plates and Microbiology Media, Available here.
2.”Nutrient Broth”, VirtualUnknownTMMicrobiology, Available here.

Image Courtesy:

1. “K pneumoniae M morganii providencia styphimuriuma” By User:Eukaryotica – Own work (Public Domain) via Commons Wikimedia
2. “Lab Bottles” by Anthony D’Onofrio (CC BY 2.0) via Flickr