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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".

[edit] Microbiology

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.

[edit] Other uses

Physcomitrella patens plants growing axenically on an agar plate (9 cm diameter)

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.

[edit] References

1. ^ Petri dish in the American Heritage Dictionary

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