A Petri dish (or cell culture dish) is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells. It was named after German bacteriologist Julius Richard Petri[1], who invented it when working as an assistant to Robert Koch. Glass Petri dishes can be reused by sterilization (for example, in an autoclave or by dry heating in a hot air oven at 160°C for one hour). For experiments where cross-contamination from one experiment to the next can become a problem, plastic Petri dishes may have to be disposed of after one use.
Modern Petri dishes often have rings on the lids and bases which allow them to be stacked so that they do not slide off one another. Multiple dishes can also be incorporated into one plastic container to create what is called a "multi-well plate".
For microbiology, agar plates are very frequently used. The dish is partially filled with warm liquid agar along with a particular mix of nutrients, sheep blood, salts, sugars, dyes, indicators and amino acids and, optionally, antibiotics. After the agar solidifies, the dish is ready to receive a microbe-laden sample. Petri plates are incubated upside down (agar on top) to keep the weight in the lid for sterility, and so excess water accumulates away from the bacterial colonies.
Other Petri dish uses do not involve agar; for instance, cell culture.
As well as making agar plates, empty Petri dishes may be used to observe plant germination or small animal behavior, or for other day-to-day laboratory practices such as drying fluids in an oven and carrying and storing samples.
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Named after the German bacteriologist Julius Richard Petri.
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Petri dish (plural Petri dishes)
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[[File:|thumb|right|200px|This is a Petri dish.]]
A petri dish is a small dish shaped like a cylinder. Scientists use it to grow cells from animals, fungus, and diseases so they can study them. They are usually made of glass or plastic. The glass ones can be used again if they are heated at 160°F. Sometimes people fill them with agar, which helps cells grow. These are called 'agar plates'. Many people use them in science classes at school. They have lids so germs in the air can not get into them, or contaminate them, and ruin the experiment.
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