10 Common Types of Bacterial Culture Media: Formulas, Preparation Methods and Characteristics

Ten Common Types of Bacterial Culture Media

1.Nutrient Agar (NA)

Formula:

Beef extract: 3g

Peptone: 5g

Sodium chloride: 5g

Agar: 15-20g

Distilled water: 1000mL

Preparation Method:

Add all components to water and heat while stirring until completely dissolved.

Adjust the final volume to 1000mL.

Dispense into containers and sterilize by autoclaving at 121°C for 15 minutes.

Characteristics:

Commonly used for cultivating bacteria without special nutritional requirements.

Suitable for isolating and culturing general bacteria, such as Escherichia coli.

2.Nutrient Broth (NB)

Formula:

Beef extract: 3g

Peptone: 5g

Sodium chloride: 5g

Distilled water: 1000mL

Preparation Method:

Dissolve all components in water and mix thoroughly.

Adjust the final volume to 1000mL, dispense into containers, and autoclave at 121°C for 15 minutes.

Characteristics:

A liquid medium used for bacterial liquid culture or metabolic studies.

3.Luria-Bertani Medium (LB)

Formula:

Peptone: 10g

Yeast extract: 5g

Sodium chloride: 10g

Agar (for solid medium): 15g

Distilled water: 1000mL

Preparation Method:

Dissolve peptone, yeast extract, and sodium chloride in water. Add agar for solid medium.

Heat and stir until fully dissolved, adjust the final volume to 1000mL.

Sterilize by autoclaving at 121°C for 15 minutes.

Characteristics:

A general-purpose medium suitable for both Gram-positive and Gram-negative bacteria, such as E. coli.

Widely used in molecular biology experiments and general bacterial culture.

4.Blood Agar (BA)

Formula:

Nutrient agar base: 40g

Fresh sheep blood: 50mL

Distilled water: 950mL

Preparation Method:

Prepare the base medium following the nutrient agar recipe. Sterilize by autoclaving and cool to 50°C.

Add sterile fresh sheep blood, mix well, and pour into plates.

Characteristics:

Supports the growth of most pathogenic bacteria (e.g., hemolytic streptococci).

Allows observation of hemolysis patterns: α-hemolysis, β-hemolysis, or γ-hemolysis.

5.MacConkey Agar (MAC)

Formula:

Peptone: 17g

Proteose peptone: 3g

Lactose: 10g

Bile salts: 1.5g

Neutral red: 0.03g

Sodium chloride: 5g

Agar: 13.5g

Distilled water: 1000mL

Preparation Method:

Dissolve all components in water while heating and stirring.

Adjust the final volume to 1000mL, autoclave, and pour plates after cooling.

Characteristics:

A selective medium inhibiting Gram-positive bacteria.

Used for isolating Gram-negative intestinal bacteria (e.g., E. coli), with lactose-fermenting colonies appearing red.

6.Triple Sugar Iron Agar (TSI)

Formula:

Glucose: 1g

Lactose: 10g

Sucrose: 10g

Beef extract: 3g

Peptone: 20g

Sodium thiosulfate: 0.3g

Sodium chloride: 5g

Ferrous salts: 0.2g

Phenol red: 0.024g

Agar: 15g

Distilled water: 1000mL

Preparation Method:

Dissolve all components in water, dispense into tubes, and solidify in a slant-deep configuration.

Sterilize by autoclaving at 121°C for 15 minutes.

Characteristics:

Detects sugar fermentation and hydrogen sulfide production.

Commonly used for intestinal bacteria identification.

7.Salmonella-Shigella Agar (SS)

Formula:

Peptone: 5g

Lactose: 10g

Bile salts: 8.5g

Sodium thiosulfate: 8.5g

Ferric chloride: 1g

Agar: 15g

Neutral red: 0.025g

Distilled water: 1000mL

Preparation Method:

Dissolve ingredients in water, sterilize by autoclaving, and pour into plates.

Characteristics:

A selective medium for isolating Salmonella and Shigella.

Lactose-fermenting colonies appear red, and Salmonella produces black colonies.

8.Tryptic Soy Agar (TSA)

Formula:

Tryptone: 15g

Yeast extract: 5g

Sodium chloride: 5g

Agar: 15g

Distilled water: 1000mL

Preparation Method:

Dissolve all components in water, adjust to 1000mL, and autoclave.

Pour into plates after cooling.

Characteristics:

A general-purpose medium suitable for various bacterial species.

Widely used in microbial testing and strain storage.

9.De Man, Rogosa, and Sharpe Agar (MRS)

Formula:

Glucose: 20g

Peptone: 10g

Yeast extract: 4g

Beef extract: 10g

Ammonium citrate: 2g

Dipotassium phosphate: 2g

Magnesium sulfate: 0.2g

Manganese sulfate: 0.05g

Agar: 15-20g

Distilled water: 1000mL

Preparation Method:

Dissolve components in water, sterilize by autoclaving, and pour into plates.

Characteristics:

Specifically designed for lactic acid bacteria.

Low pH inhibits the growth of other bacteria.

10.Cellulose Decomposition Medium (CDM)

Formula:

Microcrystalline cellulose: 10g

Potassium nitrate: 1g

Dipotassium phosphate: 1g

Magnesium sulfate: 0.5g

Sodium chloride: 0.5g

Agar: 15-20g

Distilled water: 1000mL

Preparation Method:

Dissolve all components, sterilize by autoclaving, and pour into plates.

Characteristics:

Used for isolating cellulose-decomposing bacteria.

Supports research on cellulase activity.

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