Themes

Petri dish: characteristics, functions, examples of use

It is also called a cell culture plate or Petri dish, in honor of its inventor: the German-born scientist Julius Richard Petri. He designed it in 1877 while working in the microbiology laboratory of Nobel Robert Koch, discoverer of the Koch bacillus or tuberculosis.

Culture of bacteria in a Petri dish. Source: Ufficio Comunicazione, Azienda Ospedaliera SS. Antonio e Biagio e Cesare Arrigo, Alessandria and Biblioteca Biomedica Centro di Documentazione / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

The Petri dish has multiple applications in routine and research laboratories of microbiology, cell biology, cytogenetics, agronomy, among others.

It is essential for cultivating and isolating microorganisms, as well as for the cultivation of cells, the germination of seeds, the study of small insects, among other functions. There are plates that present an internal division, which are the double plate ones, with tracing or labels for use in automated processes.

Some plates are square and come in a wide variety of sizes. There are also transparent polystyrene or polycarbonate plastic, or disposable or reusable materials to resist sterilization processes.

Petri dish features

Scientist preparing bacteria in a Petri dish for DNA testing

Listed below are some characteristics of this particular container:

 The most used Petri dish is characterized by being a round-shaped dish that has little depth.

-It is cylindrical, although there are square versions.

-In general it is made of borosilicate glass. There are also plastic plates.

-It is reusable, since it can be subjected to cleaning and sterilization processes.

-It supports temperatures between 120 to 160 ° C.

-It also has a glass lid that closes although not hermetically. However, it allows to keep the content isolated from the environment that surrounds it. This is useful to keep the cultures sterile, also avoiding the desiccation of the samples, among other undesirable aspects.

-As it is transparent, this allows you to view or appreciate its content without having to open or uncover it.

-It is characterized by being a device whose size is 30 to 200 mm.

-It is manageable, manipulable even with one hand, since it is not very large.

-It can be stacked, or placed one on top of the other, which facilitates its storage, organization and sterilization, as they are placed on a stove or in any other device.

Features

Cell culture in a Petri dish. Source: kaibara87 / CC BY (https://creativecommons.org/licenses/by/2.0)

Cultivation of microorganisms

Petri dishes offer a wide surface area to contain or serve as a support for different solid or semi-solid culture media, which are used to seed a biological sample and support the growth of microorganisms.

A culture medium is a mixture that contains nutrients that provide what is necessary for microorganisms to feed. For example, agar (carbohydrates) and blood agar (enriched with blood) are some of the most popular culture media.

Separation or isolation

One of the main functions of Petri dishes is to be able to separate or isolate microorganisms, which are being studied, from those that are contaminants; that is, those that are not of biological interest.

They allow, under controlled conditions of temperature, pH, humidity and sterility, the growth of these microorganisms, and the obtaining of pure cultures for their study and their respective identification.

Pure cultures are obtained, since the plate facilitates the separate growth of the colonies; These are the cell clusters that originate from the multiplication of a single microorganism. This is a key step for the proper isolation and identification of pathogens, or microorganisms that are harmful to man.

This culture can be carried out for the study of different microorganisms such as bacteria, fungi, parasites and viruses. Such microorganisms are taken from different biological samples such as urine, blood, cerebrospinal fluid , among others.

Likewise, this culture is used to carry out water quality controls, food sterility controls, drugs, among other studies.

Cell culture

Petri dishes are also called cell culture plates because they are used for this purpose. Cells need a solid medium (such as agar) or liquid to grow. When solid medium is used, cells grow on the surface of the medium; while, in the case of the liquid medium, they grow at the bottom of the plate.

Microbiological studies

To obtain the growth and subsequent isolation of the microorganisms in any of the microbiological studies such as urine culture, stool cultures, blood cultures, among others, the use of Petri dishes is essential.

In these cases it is used in an inverted way so that the water does not condense and interferes with the growth of bacteria. This also facilitates the visualization and morphological characterization of the colonies that are obtained throughout the culture.

Smaller plates can be placed directly on the microscope, thus allowing observations of their contents. The density of the cultures can be measured on the plates that have gratings engraved on the bottom base.

Usage examples

Scientist examines Petri dish

Seed germination

In biology laboratories or the Petri dishes they are used to study agronomy the early stages of germination of seeds of plants with the purpose of cultivating plants from isolated cells possessing asexual reproduction.

Antibiogram

In determining the effective antibiotic against a bacterium, the antibiogram test is performed using the Petri dishes. Thanks to the transparency of these, the results obtained are evaluated very easily.

Preservation of samples

The plates are used for the conservation and transfer of samples, in such a way that they do not produce their contamination or their dehydration or desiccation.

Bacteriological analysis

They are used as spill or distribution plates for the bacteriological analysis of water samples, from various environments or from surfaces.

Detection of contaminants

They are also used to detect contamination in food, medicine, clothing and various utensils.

Parasitology and entomology

Petri dishes or plates are used in parasitology for the study of worms or nematodes. Meanwhile, in entomology they are useful for the study of small animals such as insects.

Evaporation

In chemistry laboratories they are used at room temperature or in drying ovens to carry out the evaporation of solvents. On the other hand, they can also be used to dry precipitates or small samples.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Check Also
Close
Back to top button