Composition of some microbial growth media we commonly use to culture our bacteria:

Nutrient Agar (NA)

General purpose nonselective media; supports growth of a wide variety of bacteria.

Composition of Nutrient Agar

Peptone: 0.5 %

Beef extract or yeast extract: 0.3 %

NaCl: 0.5 %

Agar: 1.5 %

Adjust pH to 7.0

Trypticase Soy Agar (TSA)

General purpose nonselective media; supports growth of a wide variety of bacteria.

Composition of trypticase soy agar

Tryptone: 1.5 %

Soytone: 0.5 %

NaCl: 0.5 %

Agar: 1.5 %

Reasoner's 2A (R2A) Agar

Frequently used for the isolation slow-growing bacteria.

Composition of R2A agar

Peptone: 0.05 %

Casamino acids: 0.05 %

Yeast extract: 0.05 %

Dextrose: 0.05%

Soluble starch: 0.05%

Dipotassium phosphate: 0.03 %

Magnesium sulfate: 0.005 %

Sodium pyruvate: 0.03 %

Agar: 1.5 %

Alkaline Nutrient Agar (ANA)

For enrichment, isolation and culture of alkaliphilic bacteria.

Composition of alkaline nutrient agar

Peptone: 0.5 %

Beef extract or yeast extract: 0.3 %

Agar: 1.5 %

After autoclaving, adjust to desired alkaline pH with sterile 10% Na₂CO₃ solution or with the following Na-sesquicarbonate solution.

Na-sesquicarbonate solution:

NaHCO3: 0.42 %

Na2CO3anhydrous: 0.53 %

Horikoshi-I

For enrichment, isolation and culture of alkaliphilic bacteria.

Composition of Horikoshi-I

Glucose: 1%

Peptone: 0.5 %

Yeast extract: 0.5 %

KH2PO4: 0.1 %

MgSO4 . 7H2O: 0.02%

Agar: 2.0 %

After autoclaving, adjust to desired alkaline pH with sterile 10% Na₂CO₃ solution.

Horikoshi-II

For enrichment, isolation and culture of alkaliphilic bacteria.

Composition of Horikoshi-II

Replace glucose with soluble starch in Horikoshi-I media described above.

Mueller Hinton Agar (MHA)

Most commonly used for antibiotic susceptibility testing.

Composition of Mueller Hinton Agar

Beef extract: 0.2 %

Acid hydrolysate of casein: 1.75 %

Starch: 0.15 %

Agar: 0.17 %

MRS agar

For lactic acid bacteria.

Composition of MRS agar

Dextrose: 2 %

Peptone: 1 %

Beef extract: 1 %

Yeast extract: 0.5 %

Dipotassium hydrogen phosphate: 0.2 %

Sodium acetate 3H₂O: 0.5%

Triammonium citrate: 0.2 %

Magnesium sulphate: 7H₂O: 0.01 %

Manganese sulphate: 4H₂O: 0.005 %

Tween-80: 0.1 %

Agar: 1-1.5 %

pH 6.25

M17 agar

For lactic acid bacteria.

Composition of M17 agar

Tryptone: 0.5 %

Soya peptone: 0.5 %

Beef extract: 0.5 %

Yeast extract: 0.25 %

Ascorbic acid: 0.05 %

Magnesium sulphate: 0.025 %

Di-sodium-beta-glycerophosphate: 0.19 %

Agar: 1.1 %

pH 6.9

To prepare 1-liter media, for example, mix and dissolve appropriate amount of all ingredients in around 800 mL of distilled water. Adjust pH as required. For solid or semi-solid media, add appropriate amount of agar. Finally add more distilled water to make 1 liter. Sterilize by steam autoclave at 121 °C and 15 psi for 15 min.

Most prepared media can be stored for a few months at 2-8 °C, preferably away from light. Many liquid broths can also be stored at room temperature (25 °C) for weeks to months. It is, however, always better to use freshly prepared media. Plates should be stored in inverted position.