- Petri dish characteristics
- Applications
- How to use Petri dishes in the culture of microorganisms
- History
- References
The Petri dish or Petri dish is a laboratory instrument of great importance in the area of biology that resembles a shallow dish.
They are transparent, to allow the growth of crops to be seen through them, and are made of glass or plastic. The former can be reused once they have been decontaminated, but the latter are often discarded.
Petri dishes with a gum agar-based medium.
Some have grooves in their base and edges, which allows them not to slip when stored. They also consist of a kind of lid.
These instruments have various uses in science. One of the best known is that of being containers for the culture of microorganisms, since they allow to isolate the object of study (bacteria and viruses generally).
They are also used to cultivate eukaryotic cells, to observe the germination process of plants, to transport and observe samples, and to dry fluids.
Petri dish characteristics
1-Petri dishes are like shallow dishes (between one and two centimeters).
2-They measure about 10 cm in diameter. This length can vary.
3-They are transparent, which allows to observe the growth of the crops.
4-They have a kind of cover, which allows to protect the crop from external agents that could contaminate it.
5-They are made of plastic or glass.
6-The plastic capsules are discarded once they have been used.
7-The glass capsules can be reused after they have been decontaminated and sterilized in an oven at 160 ° C (there are other sterilization methods).
Applications
Petri dishes are often used in biology laboratories. The most common use of these instruments is to be containers for the culture of cells and microorganisms.
In these capsules, the necessary conditions are recreated to allow the growth and development of cells. Usually they are provided with a liquid or semi-solid medium and food.
Furthermore, the fact that these capsules have a lid makes them ideal for growing crops as they will be isolated and protected from contaminating agents.
As the Petri dishes are made of transparent materials, the growth of the organism can be observed through them. In this way, the researcher can keep track of progress without opening the capsule.
The samples can be observed with a microscope directly from the Petri dish since the dimensions of the instrument allow it. Likewise, the sample can be dissected without removing it from the capsule.
They are also used to observe the growth of seeds of some plants and to observe the behavior of very small animals.
Other uses for Petri dishes are as follows:
1-Dry fluids in an oven. Only glass capsules are used for this purpose as they are heat resistant.
2-Transport and save samples.
3- Serve as a container for liquid samples to be studied with a microscope.
4-Isolate microorganisms for future studies.
How to use Petri dishes in the culture of microorganisms
For the cultivation of microorganisms, one begins by sterilizing the Petri dish. This can be done by heating it in an oven or washing it with various substances (for example, bleach). This process will remove the agents present on the surface, which could damage the crop.
Next, they proceed to create a conducive environment within the capsule. Generally, the instrument is half filled with a hot liquid based on gum agar, nutrients, salts, carbohydrates, amino acids, antibiotics, indicators and other substances necessary for the study.
Petri dishes with the gum agar mixture are stored upside down in a refrigerator. This is to avoid the risk of contamination by airborne particles, as well as water condensation that could compromise the development of microorganisms.
After some time, the agar gum cools and solidifies, which means that the capsule is ready to be used. If you want to use one of these preparations, you should remove the capsule from the refrigerator and wait until it is at room temperature.
When this occurs, the microorganisms are inoculated into the mixture. This means that the individuals to be studied are entered.
To do this, the researcher can obtain the bacteria with a cotton swab. Subsequently, this swab will be passed through the gum agar mixture.
Do not apply too much pressure with the swab, as the created medium may break. After this, the capsule is sealed to avoid contamination of the culture.
When viruses are to be grown in the Petri dishes, two phases are carried out. In the first phase, bacteria are inoculated to serve as hosts for the viruses. In the second phase, the virus is inoculated.
Depending on the microorganism cultivated, the capsules can be incubated or stored in a warm medium, to accelerate their growth.
After waiting a few days (depending on the organism), the development of the culture can be observed.
History
Petri dishes were invented by the German bacteriologist Julius Richard Petri, and it is he who gave the name to this instrument.
Before the invention of the Petri dish, other containers were used for growing cultures. However, sometimes the surface was contaminated, damaging them.
One of the most used instruments were the test tubes. These did not offer as much space as a Petri dish, which made the cultured microorganisms unable to grow efficiently.
On the other hand, even when the tubes were closed with cotton caps, the cultures became contaminated after a while. This is not the case with Petri dishes which are fitted with specialized lids.
References
- Petri dish. Retrieved on September 11, 2017, from wikipedia.org
- Petri dish. Retrieved on September 11, 2017, from merriam-webster.com
- Petri dish. Retrieved on September 11, 2017, from dictionary.com
- Petri dish. Retrieved on September 11, 2017, from dictionary.cambridge.org
- Petri Dishes. Retrieved on September 11, 2017, from thermofisher.com
- What is the function of a Petri dish? Retrieved on September 11, 2017, from reference.com
- The Numerous Uses and Methods of Using a Petri Dish. Retrieved on September 11, 2017, from sciencestruck.com.