Agar plate

Agar plate is a petri dish that contains agar as a solid growth medium plus nutrients, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics.

History

The agar plate was developed by the German physician Richard Julius Petri in 1887, while working as an assistant to Robert Koch, the founder of modern bacteriology.

Preparation and use

To prepare an agar plate, a scientist pours a liquid containing agar, nutrients, and possibly other ingredients into a petri dish, then allows the liquid to cool and solidify. Once the agar solidifies, it forms a jelly-like substance in the dish.

Microorganisms can be cultured in the agar plate by streaking a sample across the surface of the agar with an inoculating loop. The microorganisms grow into separate colonies, each a clone of the original microbe in the sample.

Types of agar plates

There are many types of agar plates, each designed for specific purposes. Some common types include:

• Nutrient agar plates: These are used to culture a wide variety of microorganisms. They contain beef extract and peptone.
• Sabouraud agar plates: These are used to culture fungi and contain antibiotics to inhibit bacterial growth.
• MacConkey agar plates: These are used to differentiate between lactose fermenting and non-lactose fermenting Gram-negative bacteria.
• Blood agar plates: These are used to culture bacteria that require blood to grow.

See also

• Petri dish
• Microbiology
• Bacteriology
• Culture (biology)

References

Agar plate Resources
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