Nutrient Agar- Principle, Composition, Preparation, Results, Uses (2022)

Table of Contents

(Video) Media Prep

What is Nutrient Agar?

Nutrient Agar is a basic culture medium commonly used for the culture of non-fastidious microorganisms, and for quality control and checking purity prior to biochemical or serological testing.

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  • Nutrient media can also be used for the cultivation of fastidious microorganism by enriching the medium with serum or blood
  • Nutrient Agar is an ideal medium for the demonstration and teaching purposes as it allows more prolonged survival of cultures at ambient temperature without the risk of overgrowth that might occur with more nutritious mediums.
  • This media has a relatively simple formula that has been retained and is still widely used in the microbiological examination of a variety of samples and is also recommended by standard methods.
  • Nutrient agar is a general-purpose media that is mostly used for routine culture or to ensure prolonged survival of microorganisms.
  • It is one of the most important and commonly used non-selective media for the routine cultivation of microorganisms.
  • Nutrient agar has been used for the cultivation and enumeration of many bacteria that are not particularly fastidious.
  • The media can be made suitable for the cultivation of other fastidious organisms by the addition of different biological fluids such as horse or sheep blood, serum, egg yolk, etc.
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Principle of Nutrient Agar

  • Nutrient agar is made with various nutrients which allow the growth of a wide variety of microorganisms that do not usually require specific nutrients or supplements.
  • The primary constituents of the media are peptone, beef extract, and agar. In addition to these nutrients, some vitamins and some trace ingredients necessary for the growth of bacteria are also added.
  • The peptone is the source of nitrogen or protein that acts as a source of amino acids for the bacteria.
  • The beef extract is the primary source of carbon which is essential for the formation of carbohydrates in the bacteria. It also contains other components like some vitamins, different trace minerals, organic compounds, and salts, which further enhance the growth of different organisms.
  • Besides, sodium chloride is added to the medium in order to maintain the osmotic equilibrium of the medium and prevent the change in pH of the medium during growth.
  • The distilled water provides a medium to dissolve the nutrients so that it is easier for the bacteria to absorb them.
  • Agar is the solidifying agent that provides a stable surface for the organism to grow on, which allows for the observation of colony morphology and enumeration of the organism.
  • The medium is made up of basic nutrient that is essential for a wide variety of organism, which makes it a general media that can be used for various purposes.

Composition of Nutrient Agar

  • Most nutrient agar used these days in laboratories is prepared from the dehydrated powder supplied by different vendors. The composition of the media, however, remains the same.
  • It can also be prepared in the lab if the necessary constituents of the media are available.
  • The following is the composition of the nutrient agar:
S.NIngredientsGram/liter
1.Peptone5.0
2.Yeast extract1.5
3.Beef extract1.5
4.Sodium chloride5.0
5.Agar15.0
Final pH at 25°C: 7.4 ±0.2

Preparation of Nutrient agar

  1. In a beaker, 28 grams of the dehydrated powder or lab-prepared media is added to 1000 milliliters of distilled or deionized water.
  2. The suspension is then heated to boiling to dissolve the medium completely.
  3. The dissolved medium is then autoclaved at 15 lbs pressure (121°C) for 15 minutes.
  4. Once the autoclaving process is complete, the beaker is taken out and cooled to a temperature of about 40-45°C.
  5. If enrichment is desired, the addition of blood or biological fluids can be done after the autoclaving process.
  6. The media is then poured into sterile Petri plates under sterile conditions.
  7. Once the media solidifies, the plates can be placed in the hot air oven at a lower heat setting for a few minutes to remove any moisture present on the plates before use.

Storage of Nutrient agar

  • The media in the powder form should be stored between 10 to 30°C in a tightly closed container, and the prepared medium should be stored at 20-30°C.
  • After opening, the product should be appropriately stored when dry, after tightly capping the bottle in order to prevent lump formation as the medium is hygroscopic in nature and thus, absorbs moisture relatively quickly.
  • The container should be stored in a dry ventilated area protected from extremes of temperature and sources of ignition.
  • The product should be used before the expiry date on the label.

Result Interpretation onNutrient agar

Nutrient Agar- Principle, Composition, Preparation, Results, Uses (1)

Image Source: Eukaryotica and TM Media.

The media forms light yellow colored clear to slightly opalescent gel on Petri plates after colling. The following table demonstrates the growth of important medical bacteria with their colony morphologies on Nutrient Media:

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S.NOrganismGrowthColony Morphology
1.Escherichia coliGood-luxuriantGreyish to white-colored large, circular and convex colonies; smooth and rough colonies.
2.Salmonella TyphiGood-luxuriantSmooth colorless colonies with a diameter range of 2-4 mm.
3.Staphylococcus aureusGood-luxuriantGolden yellow colored circular, convex and smooth colonies of the diameter range of 2-4 mm; opaque colonies.
4.Streptococcus pyogenesGood-luxuriantCircular, pinpoint colonies of the size 0-5 to 1 mm in diameter; light yellow colored with low convex elevation; matt surface in virulent strains but glossy surface are seen in non-virulent strains; mucoid colonies in the case of capsule production.
5.Pseudomonas aeruginosaGood-luxuriantLarge, opaque, flat colonies with irregular margins and distinctly fruity odor; variable pigment production; virulent strains might produce mucoid colonies.
6.Klebsiella pneumoniaeGood-luxuriantCircular, dome-shaped, mucoid, translucent or opaque greyish white colonies; 2-3 mm diameter
7.Yersinia pestisGood-luxuriantTiny, almost invisible, shiny grey, translucent “spots’; 1 to 2 mm irregular, grey-white to slightly yellow in color with raised, irregular, “fried egg” appearance, which becomes prominent as the culture ages.

Uses of Nutrient agar

  • Nutrient agar is used for the culture of less fastidious organisms as a general medium.
  • It is also used for routine culture of microorganisms from typical environmental samples like water, food, and even air.
  • Nutrient agar is often used for the demonstration and teaching purposes as it doesn’t contain harmful substances and can be used for the isolation of multiple microorganisms.
  • The use of Nutrient agar is recommended by standard methods as it has a simple composition which can even be prepared within a laboratory.
  • It can also be used for the preservation of microorganisms for an extended period of time without contamination that might occur in a more nutritious medium.
  • It is used as a purity testing method prior to the different biochemical tests and serological tests.
  • It is one of the most common media used for the enumeration of bacteria from environmental samples.
  • The addition of biological fluids like horse or sheep blood, serum, egg yolk, etc. to the nutrient agar makes the medium more selective for certain fastidious organisms.

Limitations of Nutrient agar

  • Different organisms might differ in their growth requirement and may show variable growth patterns on the medium. This makes the medium quite unreliable during isolation.
  • Because nutrient media supports the growth of many microorganisms, chances of contamination are quite high during isolation.
  • It cannot be used as a selective medium for the cultivation of fastidious organisms that have particular nutrients requirements.
  • Nutrient agar mostly only allows the isolation of bacteria and not other microorganisms like fungi.
  • In some cases, some microorganisms might demonstrate similar colony morphologies on nutrient agar which makes it difficult to distinguish them without microscopic examination.

References and Sources

  • Nutrient Agar. TM Media.
  • 4% – https://microbenotes.com/enterobacteriaceae-cultural-characteristics/
  • 4% – http://www.himedialabs.com/TD/M001.pdf
  • 2% – http://himedialabs.com/TD/EC002M.pdf
  • 1% – https://www.sigmaaldrich.com/analytical-chromatography/microbiology/microbiology-products.html?TablePage=17997595
  • 1% – https://us.vwr.com/assetsvc/asset/en_US/id/8040947/contents
  • 1% – https://microbeonline.com/nutrient-agar-composition-preparation-uses/
  • 1% – https://mafiadoc.com/3-materials-and-methods-shodhganga_5ba00edc097c471a388b4623.html
  • 1% – http://www.himedialabs.com/TD/MV1058.pdf
  • 1% – http://www.himedialabs.com/TD/M351.pdf
  • <1% – https://www.slideshare.net/UmeshMaskare/culture-media-for-different-microorganism
  • <1% – https://www.sigmaaldrich.com/analytical-chromatography/microbiology/microbiology-products.html?TablePage=18176518
  • <1% – https://www.sas.upenn.edu/LabManuals/biol275/Table_of_Contents_files/2-PreparationOfMedia.pdf
  • <1% – https://www.researchgate.net/post/What_are_the_differences_between_peptone_tryptone_tryptone_peptone_trypticase_and_trypticase_peptone2
  • <1% – https://quizlet.com/125332332/exercise-19-enumeration-of-bacteria-flash-cards/
  • <1% – https://microbiologyinfo.com/nutrient-agar-composition-preparation-and-uses/
  • <1% – https://microbenotes.com/nutrient-agar-principle-composition-preparation-and-uses/
  • <1% – https://med.libretexts.org/Courses/American_Public_University/APUS%3A_An_Introduction_to_Nutrition_(Byerley)/Text/10%3A_Water%2C_Electrolytes%2C_Acid-Base_Balance/10.05%3A_Electrolytes_Important_for_Fluid_Balance
  • <1% – https://legacy.bd.com/europe/regulatory/Assets/IFU/Difco_BBL/274610.pdf
  • <1% – https://courses.lumenlearning.com/microbiology/chapter/media-used-for-bacterial-growth/
  • <1% – http://www.personal.psu.edu/faculty/k/h/khb4/enve301/301labs/lab4pureculture.html
  • <1% – http://eacharya.inflibnet.ac.in/data-server/eacharya-documents/53e0c6cbe413016f234436f5_INFIEP_17/7/ET/17-7-ET-V1-S1__l-7_theory_the_preservation_of_microbes.pdf
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(Video) Preparation of nutrient agar plates l How to make agar plate

FAQs

What are the uses of nutrient agar? ›

Nutrient agar is a general purpose medium that supports the growth of a wide range of non-fibrous organisms. Nutrient agar is popular because it supports the growth of various types of bacteria and fungi, and contains many of the nutrients necessary for the growth of bacteria.

What is the principle of nutrient agar? ›

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.

What are the composition of nutrient agar? ›

It typically contains (mass/volume): 0.5% peptone - this provides organic nitrogen. 0.3% beef extract/yeast extract - the water-soluble content of these contribute vitamins, carbohydrates, nitrogen, and salts. 1.5% agar - this gives the mixture solidity.

What is preparation of nutrient agar? ›

How to prepare nutrient agar? Suspend 28g of nutrient agar powder (CM0003B) in 1L of distilled water. Mix and dissolve them completely. Sterilize by autoclaving at 121°C for 15 minutes. Pour the liquid into the petri dish and wait for the medium to solidify.

What is nutrient agar test? ›

Nutrient Agar is a basic culture medium commonly used for the culture of non-fastidious microorganisms, and for quality control and checking purity prior to biochemical or serological testing.

What is the principle of culture media? ›

Principle: In preparing a culture medium for any microorganism, the primary goal is to provide a balanced mixture of the required nutrients, at concentrations that will permit good growth. No ingredient should be given in excess because many nutrients become growth inhibitory or toxic as the concentration is raised.

What is the composition of nutrient broth? ›

Nutrient Broth has the same formulation as Nutrient Agar, only agar has been omitted (which causes the medium to solidify at room temperature). It is made from a mixture of Tryptone and meat extract which helps in the growth of microorganisms. Sodium chloride is intended for maintaining osmotic pressure.

What are the uses of nutrient broth? ›

Uses. Nutrient Agar/broth is the simplest and most common medium in routine diagnostic laboratories. It is ideally used for the isolation, cultivation and maintenance of non-fastidious organisms. It is used for checking the purity of the culture prior to biochemical or serological testing.

Is nutrient agar selective media? ›

Notice that nutrient agar is neither a selective nor differential medium.

What are the composition of culture media? ›

1 Nutrients: proteins/peptides/amino-acids. 2 Energy: carbohydrates. 3 Essential metals and minerals: calcium, magnesium, iron, trace metals: phosphates, sulphates etc. 4 Buffering agents: phosphates, acetates etc.

Why is agar used in microbiology? ›

The addition of agar-agar (a complex carbohydrate extracted from seaweed) results in a solid medium. Agar is an ideal solidifying agent for microbiological media because of its melting properties and because it has no nutritive value for the vast majority of bacteria.

What is the composition of 100ml nutrients agar plate? ›

IngredientsQuantity (100 mL)
Yeast Extract0.2 g
Sodium Chloride0.5 g
Agar1.5 g
pH7
1 more row

How is nutrient agar prepared in the lab? ›

How to Make Nutrient Agar - YouTube

What is the pH of nutrient agar? ›

Nutrient Agar, pH 6.8 has relatively simple formulation which provides the necessary nutrients for the growth of many microorganisms which are not very fastidious. Many bacteria have the optimum pH growth range of 6.6 to 7.0.

What color is nutrient agar? ›

The color of nutrient agar and broth inoculated with G-ve cocci were changed to green color.

Why is nacl used in nutrient agar? ›

The presence of sodium chloride in nutrient agar maintains a salt concentration in the medium that is similar to the cytoplasm of the microorganisms. If the salt concentration is not similar, osmosis takes place transporting excess water into or out from the cell.

What is the pH of nutrient broth? ›

Nutrient Broth, pH 6.9 without NaCl
Quality Control
AppearanceCream to yellow homogeneous free flowing powder
ReactionReaction of 0.8% w/v aqueous solution at 25°C. pH : 6.9±0.2
pH6.70-7.10
Cultural ResponseCultural characteristics observed after an incubation at 35-37°C for 18-48 hours.
7 more rows

What are the types of culture media? ›

Culture media are divided into three types; solid medium, semi-solid medium, and liquid medium, based on consistency. The percentage of agar used determines the consistency of the medium.

What are the 3 main types of microbiological culture media? ›

Depending upon the addition and quantity of this substance, media are of three types:
  • 3.3.1 Liquid (Broth) Media. Liquid (Broth) Media, such as nutrient broth , tryptic soy broth or glucose broth which are prepared without the use of agar agar. ...
  • 3.3. 2 Semisolid Media. ...
  • 3.3. 3 Solid Media.
19 Sept 2020

What are the uses of culture media? ›

Culture media are used for quality control tests of nonsterile raw materials and finished products as well as for microbial contamination (sterility) tests in applications such as hygiene monitoring, sterilization process validation and determination of the effectiveness of preservatives and antimicrobial agents.

What are the 3 types of bacterial culture media? ›

Based on consistency culture media is classified as liquid, semi-solid and solid media.

Is nutrient agar solid or liquid? ›

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.

What type of media is nutrient broth? ›

B.

Complex media: These are media containing nutrients in unknown quantities that are added to bring about a particular characteristic of a microbial strain. Examples are tryptic soy broth, blood agar, and nutrient broth.

What is the difference between agar and broth? ›

The only difference between broth and agar media is that broths do not contain an agar component. We use broth tubes primarily for specific assays, or (rarely) for bacteria that will not form colonies on a solid surface.

Why is blood agar used? ›

Blood agar is used to grow a wide range of pathogens, especially those that are more difficult to grow, such as Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species. It is also necessary to detect and differentiate haemolytic bacteria, particularly Streptococcus species.

What is liquid media used for? ›

Liquid media are a type of culture media used to cultivate and maintain microorganisms. They are also referred to as culture broths. Liquid media are not supplemented with a solidifying agent. Hence, these media remain as liquids even at room temperature.

Why are the nutrient agar plates used in this experiment? ›

 The nutrient agar plates are used in this experiment because they allow the growth of bacteria and compare the different types of growth.

What is the principle of selective media? ›

Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present.

How is nutrient agar culture media prepared? ›

Preparation of nutrient agar
  1. Suspend 28.0 grams in 1 litre of purified/distilled or deionized water.
  2. Heat to a boil to completely dissolve the medium.
  3. Sterilize by autoclaving at a pressure of 15 lb (121°C) for 15 minutes.
  4. After autoclaving, cool to 45-50°C.

What bacteria can grow on nutrient agar? ›

What Grows on Nutrient Agar? Microorganisms need food, water and a suitable environment in order to survive and grow. Nutrient agar provides these resources for many types of microbes, from fungi like yeast and mold to common bacteria such as Streptococcus and Staphylococcus.

What are the uses of nutrient broth? ›

Uses. Nutrient Agar/broth is the simplest and most common medium in routine diagnostic laboratories. It is ideally used for the isolation, cultivation and maintenance of non-fastidious organisms. It is used for checking the purity of the culture prior to biochemical or serological testing.

Why are the nutrient agar plates used in this experiment? ›

 The nutrient agar plates are used in this experiment because they allow the growth of bacteria and compare the different types of growth.

What is the purpose of agar in culture media? ›

The addition of agar-agar (a complex carbohydrate extracted from seaweed) results in a solid medium. Agar is an ideal solidifying agent for microbiological media because of its melting properties and because it has no nutritive value for the vast majority of bacteria.

What bacteria grows on nutrient agar? ›

What Grows on Nutrient Agar? Microorganisms need food, water and a suitable environment in order to survive and grow. Nutrient agar provides these resources for many types of microbes, from fungi like yeast and mold to common bacteria such as Streptococcus and Staphylococcus.

What is the pH of nutrient agar? ›

Nutrient Agar, pH 6.8 has relatively simple formulation which provides the necessary nutrients for the growth of many microorganisms which are not very fastidious. Many bacteria have the optimum pH growth range of 6.6 to 7.0.

What is the composition of nutrient broth? ›

Ingredients
Ingredient1 L500 mL
beef extract1 g0.5 g
Yeast extract2 g1 g
Peptone5 g2.5 g
Sodium chloride (NaCl)5 g2.5 g
1 more row
5 Aug 2011

Why is peptone used in nutrient agar? ›

Peptone. Peptone is a mixture of proteins and amino acids that is obtained by breaking down natural products such as animal tissues, milk and plants. The function of peptone in nutrient agar is to provide a protein source so that micro-organisms can grow.

Is nutrient agar selective or differential? ›

Notice that nutrient agar is neither a selective nor differential medium.

Why is agar used to grow bacteria? ›

Agar, which is a polysaccharide derived from red seaweed (Rhodophyceae) is preferred because it is an inert, non-nutritive substance. The agar provides a solid growth surface for the bacteria, upon which bacteria reproduce until the distinctive lumps of cells that we call colonies form.

What is agar and its uses? ›

Agar (agar agar) is a gelatinous substance that is extracted from seaweed and processed into flakes, powders and sheets. It is commonly used in Asian cuisines and as a flavorless vegan substitute for gelatin.

Why is agar used? ›

Agar helps gel, stabilize, texturize and thicken beverages, baked goods, confectioneries, dairy products, dressings, meat products and sauces. Agar gels at low concentrations; the gel is opaque in color and chewy in texture, making it versatile in both cold and hot dishes.

What is agar write its uses? ›

Best known as a solidifying component of bacteriological culture media, it is also used in canning meat, fish, and poultry; in cosmetics, medicines, and dentistry; as a clarifying agent in brewing and wine making; as a thickening agent in ice cream, pastries, desserts, and salad dressings; and as a wire-drawing ...

What color is nutrient agar? ›

The color of nutrient agar and broth inoculated with G-ve cocci were changed to green color.

How many types of agar are there? ›

Types of agar
S. No.Type of AgarBacterial studies
3Chocolate agarSupport growth of Haemophilus species and Neisseria
4MacConkey agarSupports the growth of gram-negative bacteria
5Nutrient agarTo grow different type of bacteria (not all) and some fungi
6Neomycin agarTo culture microorganisms anaerobically
2 more rows
30 Mar 2021

Is nutrient agar solid or liquid? ›

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.

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