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petri dish

Primary Information
Secondary Information

Definition

A petri dish is a shallow, round dish with a lid that is used to grow microorganisms in a controlled environment. It is made of glass or plastic and has a flat bottom and a slightly curved lid. The lid helps to keep the microorganisms inside the dish from drying out and from being contaminated by other microorganisms in the air.

Petri dishes are widely used in biology to cultivate microorganisms such as bacteria, yeasts, and moulds. They are also used in other fields, such as chemistry and genetics.

Petri dishes are prepared with a growth medium, which is a nutrient-rich agar solution. The agar solidifies when it cools, creating a solid surface on which the microorganisms can grow.

Microorganisms are added to the petri dish using a sterile loop or pipette. The microorganisms are then allowed to grow for a period of time, typically several days. During this time, the microorganisms will reproduce and form colonies.

The colonies can be observed under a microscope to identify the type of microorganism and to study its growth. Petri dishes can also be used to test the effectiveness of antibiotics or other treatments against microorganisms.

Petri dishes are a versatile and essential tool for scientists who study microorganisms. They are a reliable and affordable way to grow and study microorganisms in a controlled environment.

How can the word be used?

The Petri dish was filled with a nutrient agar that supported the growth of bacteria.

petri dish

Different forms of the word

Noun:

  • Petri dish (a shallow transparent dish with a loose cover used especially for cultures of bacteria).
  • Petri plate (a shallow transparent dish with a loose cover used especially for cultures of bacteria).

Adjective:

  • Petri dish (of or relating to a Petri dish).

Etymology

The word "Petri dish" is named after its inventor, German bacteriologist Julius Richard Petri (1852-1921). Petri did not invent the culture dish himself; rather, it was a modified version of Koch's invention which used an agar medium that was developed by Walther Hesse. Koch had published a precursor dish in a booklet in 1881 titled "Zur Untersuchung von Pathogenen Organismen" (Methods for the Study of Pathogenic Organisms), which has been known as the "Bible of Bacteriology".

The word "Petri dish" was first used in English in 1892.

Question

What are petri dishes used for?

AQA Science Exam Question and Answer

Question:

Explain the purpose of using a petri dish in laboratory experiments. Describe how Petri dishes are utilised to cultivate and study microorganisms and discuss the importance of aseptic techniques in this process.

Answer:

A petri dish serves as a versatile tool in laboratory experiments, particularly in microbiology. It provides a controlled environment for the cultivation and study of microorganisms. Petri dishes are typically made of transparent plastic or glass and are used to hold a solid medium like agar, which provides essential nutrients for microbial growth.

Microbiologists use Petri dishes to isolate culture-specific microorganisms for further study. By streaking a sample onto the agar surface, individual bacterial or fungal colonies can develop, making it easier to analyse and identify different species.

Aseptic techniques are vital when using Petri dishes to prevent contamination. Sterilising the dish and tools, such as inoculation loops, before use ensures that only the desired microorganisms grow in the culture. Opening the petri dish only briefly and avoiding contact with non-sterile surfaces minimise the risk of introducing unwanted microorganisms.

Petri dishes are also used to test the effectiveness of antimicrobial agents, study patterns of bacterial growth, and explore the impact of environmental factors on microbial development.