Nutrient Agar: Composition, Preparation and Uses

Nutrient Agar is a general purpose, nutrient medium used for the cultivation of microbes supporting growth of a wide range of non-fastidious organisms. Nutrient agar is popular because it can grow a variety of types of bacteria and fungi, and contains many nutrients needed for the bacterial growth.

Composition of Nutrient Agar

  • 0.5% Peptone

It is an enzymatic digest of animal protein. Peptone is the principal source of organic nitrogen for the growing bacteria.

  • 0.3% beef extract/yeast extract

It is the water-soluble substances which aid in bacterial growth, such as vitamins, carbohydrates, organic nitrogen compounds and salts.

  • 1.5% agar

It is the solidifying agent.

  • 0.5% NaCl

The presence of sodium chloride in nutrient agar maintains a salt concentration in the medium that is similar to the cytoplasm of the microorganisms.

  • Distilled water

Water is essential for the growth of and reproduction of micro-organisms and also provides the medium through which various nutrients can be transported.

  • pH is adjusted to neutral (7.4) at 25 °C.

Preparation of Nutrient Agar

1. Suspend 28 g of nutrient agar powder in 1 litre of distilled water.

2. Heat this mixture while stirring to fully dissolve all components.

3. Autoclave the dissolved mixture at 121 degrees Celsius for 15 minutes.

4. Once the nutrient agar has been autoclaved, allow it to cool but not solidify.

5. Pour nutrient agar into each plate and leave plates on the sterile surface until the agar has solidified.

6. Replace the lid of each Petri dish and store the plates in a refrigerator.

Uses of Nutrients Agar

1. It is frequently used for isolation and purification of cultures.

2. It can also be used as a means for producing the bacterial lawns needed for antibiotic sensitivity tests.  In actuality, antibiotic sensitivity testing is typically performed on media specially formulated for that purpose.

Pictures
Four nutrient agar plates growing colonies of common Gram negative bacteria.
Four nutrient agar plates growing colonies of common Gram negative bacteria.
Source: Wikipedia

50 thoughts on “Nutrient Agar: Composition, Preparation and Uses”

    • It may depend on the manufacturer of the brand of nutrient agar you will use. But for all the ones i have worked with, it was specified that one one should use 28g/l which would mean 14g/500ml.

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    • For 1000 ml it is 28 grams hence 500 ml requires 14 grams of nutrient agar with an extra addition of 0.5% agar to better solidification

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  1. Hello… I wonder that I can ask a question about my problems. I did subculture Bacteria Lignolytic, Selulotic and Cytophaga on Nutrient Broth. But the result the subculture turning into red. I suspected that subculture contain E.coli. I’m not sure about that.

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  2. That % mean for 1000ml or 1l you need that particular amount of any substance,like peptone for Nam that is 5gm for 1000ml . Now if you have to prepare low amount of medium then you have to reduce the %. Here you mentioned for 1l media you have to add 1% malt extract for 500lm media it’ll be .5% of malt extract.. That’s how it works

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      • I have heard from several growers to prepare this with brewers yeast, bees pollen, and shaved coconut. You blend the pollen and coconut. Then you add the brewers yeast. This all gets mixed into the agar mixture and it must be Prepared before you begin the agar. add 5% gypsum and 5% activated charcoal by your measurement. So in grams. Also this is a recipe for growing mushrooms. This would be a ph balanced substrate and it would be loaded with a blend of complex polysaccharides, omega-3, the immunological benefits of the bees pollen. Once you pour the dishes let it cool as this instruction says. You need to Pasteurize though, do not sterilize. The reason is because you kill all good and all bad microbes. When you pasteurize you kill the bad and leave the good. So it is recommended to pressure cook at 0 psi and I apologize I only know °F but you bring it to 145 and then turn the heat down or off. The heat will continue to climb up to between 165 -175 °F. After this cools down to roughly 70°F you would then inoculate the agar dishes and close the lids for the final time with polypore tape. This from my understanding is a master mix for agar. Dubbed WhittingtonsMastersMix or WMM for short… feel free to copy the recipe. Anyone can make this at home. Hope to see the research on medicinal mushrooms continuing to expand or health, or longevity, our nerves, please get a hold of some research about Chaga, Reishe, Lions Mane, or Gametes Trametes better know as the turkey tail. Also look into the Studies being down in Oakland on the Psilocybe mushrooms as the new law that decriminalized mushrooms and other plants. The time for research is now! And Remember!! TRYING IS POWERLESS, IT IS ONE FOOT IN AND ONE FOOT OUT. IT IS INDECISION. IT IS YOUR SELF GETTING IN YOUR WAY. IT IS INDECISION. DECIDE TO DO. THE POWER TO TAKE BACK CONTROL OF YOUR LIFE IS TAKING OWNERSHIP OF YOUR ACTIONS AND RESPONSIBILITIES. THERE IS NO TRY, THERE IS ONLY DO. I wish you all the best in life, in love, in health in all its’ forms. Peace and blessings. May your consciousness be ever hungry for growth!

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  3. If possible could you add me to the group? I am an aspiring Microbiologist and hope to get more insight or even help in the field and my studies. Thank you, 07756316834.

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  5. Agar are come from huge agar plant know as kelps .are cooked with dilute acid and filtered the acidic liquid is neutralized and cooled so that agal gel is obtained

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  6. To prepare 1 L media we need yeast extract 0.4%. malt extract 1%, and glucose 0.4%.

    My question is: what does % mean?
    Thanks.

    Reply
  7. Sir I have used nutrient agar for fungus culture…. Before i use PDA for culture it was gud…. But i found lots of bacterial contamination in my Nutrient agar culture…. Does the composition of beef extract hampers the groeth of fungus and favours bacteria instead.

    Reply
  8. Hello I have a question. If a leg wound is cultured and it is put on a nutrient agar, Selective agar and Differential Agar what are expected to show?

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  9. Hi ! I streaked out from sweet potato steep water and I had both red colonies and white colonies that turned nutrient agar kind of green. Please what kind of organisms are these . They areboth staining gram positive

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  10. Nutrient agar favored 4 Non fastidious bacteria
    Blood agar used to detect bacteria that produce enzymes to break apart the Red blood cells
    Mac conkey agar favored 4 gram – bacteria
    sabouraud agar favoured 4 fungi
    lowenstein jensen agar favored 4 mycobacterium tuberculosis
    salmonella shigella agar favored in the isolation of salmonella&shigella

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  11. the compositon and funtions were helpful. but i dont really get the beef extract could you please explain more. you did a nice job. my name is Anie, 19yr old microbiology student, i’m currently in my 3rd year in Uni

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  12. among the types of medias we have can somebody help me and tell me the kind of micro organism to which each media favour the growth
    eg nutrient agar favour the growth of …..

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  13. Sir/Madam,
    Could u tell me what are the microbial techniques? Just list put techniques name so that i could learn it from basics.

    Thank you

    Reply
    • Could u tell me what are the microbial techniques? Just list out the techniques name so that i could learn it from basics.

      Reply

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