Petri dish : Definition, Types and Uses
◉ What is a Petri dish ?
A Petri dish is a cylindrical lidded dish made of shallow clear glass or plastic, used to hold a thin layer of agar. Used to cultivate bacteria, fungi and other microorganisms.
The Petri dish is named after its inventor, Julius Richard Petri (1852-1921) who worked as an assistant to Robert Koch in Berlin at the Imperial Health Office. He developed a double dish, small, round, flat-bottomed with sides. One of the two dishes was slightly larger, serving as a lid and a shield. Designed with two basic principles:
- Separation : Cultivating microorganisms while separating them from airborne contaminants, and after culture, separating individuals (handlers) and the environment from these bacteria.
- Transparency / Visibility : It allowed researchers to easily observe and study microorganisms in a controlled environment.
Petri originally called the dish a "cell culture dish," but it eventually became known as a Petri dish in his honor.
◉ Petri dish uses
Petri dishes have a wide range of uses, mainly in the laboratory, including :
- The Petri dish is used to cultivate microorganisms while separating them from airborne contaminants. They provide a controlled environment for the growth of these organisms, which can then be used for further study or testing.
- Antibiotic susceptibility testing : Petri dishe can be used, with Agar and antibiotic discs, to test the effectiveness of different antibiotics against bacterial cultures and choosing the right antibiotic treatment.
- It can be used as a support to dissect the sample for further studies.
- Petri dishes can be utilized for culturing animal and plant cells, which enables researchers to observe the growth and behavior of cells under controlled conditions.
- Safety in laboratory : helps separate individuals from unknown bacteria that can easily spread and cause disease.
- It is used in schools and colleges to observe the germination of seeds for example.
◉ Types of petri dishes
Petri dishes are available in a variety of shapes, sizes and materials. The choice of petri dish used depends on the specific application and the needs of the laboratory. Here are some common types of petri dishesc:
Size : They come in various sizes, ranging from a few millimeters to several centimeters in diameter:
- Small dishes come with 35 mm in diameter.
- 90mm is the most size commonly used in microbiology.
- 100mm Petri Dish, used for larger bacterial colonies and for culturing cells for tissue culture experiments.
- The largest size is 150mm, used for growing large colonies or cultures of cells, such as plant cells or yeast.
Shape : Petri dishes are typically circular in shape, but some specialty petri dishes may have other shapes. Researchers choose the shape of the petri dish based on the specific requirements of their experiment :
- Round Petri dish is the most common shape.
- Square shape.
- Rectangular shape.
Material : petri dishes can be made from a variety of materials, including :
- Glass : Typically use borosilicate glass. Glass petri dishes are durable and can be sterilized by heat, chemical sterilization, or radiation. They are typically reusable and have a smooth, non-porous surface that is easy to clean. Glass petri dishes are useful for applications that require high temperatures or harsh chemicals, and they are often used in research and academic settings.
- Polystyrene : Polystyrene petri dishes are lightweight, disposable, and inexpensive. They are widely used in clinical and industrial settings for routine microbiological testing. Polystyrene petri dishes are available with different surface treatments, such as tissue culture treated, non-treated, or low adhesion, to promote cell attachment or prevent cell attachment depending on the specific application.
- Polypropylene : Polypropylene petri dishes are more resistant to heat and chemicals than polystyrene dishes. They are also lighter and more durable than glass petri dishes, making them a popular choice for field work, environmental testing, and industrial applications.
- Cellulose acetate : Cellulose acetate petri dishes have a higher gas permeability than other types of petri dishes, making them useful for applications that require high oxygen or carbon dioxide levels. They are also resistant to many chemicals and can withstand high temperatures.
Surface : The surface of a petri dish can be smooth or have a textured surface. Textured surfaces can promote the growth of certain microorganisms or help to prevent bacterial swarming.
Lid : Petri dish lids can be solid, vented, or semi-permeable. Vented lids allow for gas exchange and are useful for growing anaerobic microorganisms, while semi-permeable lids can control the humidity level in the dish.
Stacked petri dish : This type of petri dish has multiple compartments that can be stacked on top of each other, allowing for efficient use of space in crowded laboratory environments.
Sections : Some petri dishes have sections or compartments that allow for multiple types of media to be used on a single plate or for testing multiple samples at once.
Coated petri dishes are petri dishes that have been treated with a layer of material (such as collagen, fibronectin, laminin, or extracellular matrix proteins) that is designed to promote cell attachment and growth.
Different types of petri dishes
- Made of 100% virgin polystyrene in 35/50/70/90/150 mm and personalized
- Designed with a writing area
- Opens easily with one hand
- Gamma irradiation for sterilization
- Packaged in heavy-walled polyethylene sleeves
- Special design features for 90mm x 15mm petri dish
- Digital scale, quadrants for easy orientation and counting
- The special design (stacking ring) allows easy and stable stacking
◉ Frequently Asked Questions
What is in a Petri dish to grow bacteria ?
A Petri dish used for culturing bacteria usually contains agar which provides the nutrients and environment necessary for bacterial growth. Different types of agar with different compositions (beef extract, peptone, salt, etc) are used depending on the bacteria to be searched for.
Can polypropylene Petri Dish be autoclavable ?
Yes, Polypropylene Petri dishes are generally autoclavable. Polypropylene is a type of plastic that is heat-resistant and can withstand high temperatures without melting or deforming. However, it is important to check the manufacturer's instructions
Can I use petri dish for cell culture ?
Yes, they are commonly used for cell culture in research and clinical laboratories. However, it is important to choose the right type of petri dish and ensure that it is sterile before use.
Can plastic petri dish be autoclaved?
Disposable plastic petri dishes cannot be sterilized in an autoclave as they will melt.
Petri dish, a petri plate or cell-culture dish, are commonly used to refer to the same item : a shallow cylindrical containers with fitted lids.