Closed by a transparent lid of a similar shape, but slightly larger in diameter. Used in microbiology and chemistry.

History

Modifications

The Petri dish is usually made of clear glass or plastic (clear polystyrene) and comes in a variety of sizes. The most commonly used options have a diameter of about 50-100 mm and a height of about 15 mm.

Application

The cup is widely used in microbiology for culturing colonies of microorganisms. To do this, it is filled with a layer of nutrient medium, on which the culture of microorganisms is sown.

Glass dishes are reusable but require sterilization before re-inoculation. Cups made of plastic materials are supplied sterile, in sealed packaging.

In addition, the Petri dish is often used for applied purposes, such as evaporating liquids, storing small fragments of various preparations, dissecting small animals and plants, and etching small printed circuit boards.

Often, Petri dishes are used in terrariums for a “nesting base” when breeding amphibians (dart frogs, leaf climbers and other animals).

see also

Chemical laboratory equipment Glassware Separation equipment Measuring Various equipment Security

Write a review on the article "Petri Dish"

An excerpt characterizing the Petri dish

The cavalry guard officer, sitting on horseback, rode to another.
- No, they left.
“How could I not be responsible for the delay! That's a shame!" thought the officer. He traveled all over the camp. Who said that they saw Yermolov drive somewhere with other generals, who said that he was probably at home again. The officer, without dinner, searched until six o'clock in the evening. Yermolov was nowhere to be found and no one knew where he was. The officer had a quick bite to eat with a comrade and went back to the vanguard to Miloradovich. Miloradovich was also not at home, but then he was told that Miloradovich was at General Kikin's ball, and that Yermolov must be there too.
– Yes, where is it?
- And over there, in Echkin, - said the Cossack officer, pointing to a distant landowner's house.
- But what about there, behind the chain?
- They sent two regiments of ours to the chain, there is such a spree now, trouble! Two musics, three songbook choirs.
The officer went behind the chain to Echkin. From afar, driving up to the house, he heard the friendly, cheerful sounds of a dancing soldier's song.
“In the sledge and ah ... in the sledges! ..” - he heard with a whistle and with a torban, occasionally drowned out by the cry of voices. The officer felt cheerful at the sound of these sounds, but at the same time he was afraid that he was to blame for not transmitting the important order entrusted to him for so long. It was already nine o'clock. He dismounted from his horse and entered the porch and the hall of a large, intact landowner's house, located between the Russians and the French. In the pantry and in the antechamber, footmen bustled with wines and food. There were song books under the windows. The officer was led through the door, and he suddenly saw all the most important generals of the army together, including the large, conspicuous figure of Yermolov. All the generals were in unbuttoned coats, with red, animated faces, and laughed loudly, standing in a semicircle. In the middle of the hall, a handsome short general with a red face was briskly and deftly making a trepak.
– Ha, ha, ha! Oh yes, Nikolai Ivanovich! ha, ha, ha!
The officer felt that, entering at that moment with an important order, he was being doubly guilty, and he wanted to wait; but one of the generals saw him and, having learned why he was, told Yermolov. Yermolov, with a frown on his face, went out to the officer and, after listening, took the paper from him without saying anything to him.

Have you thought about growing a whole culture of bacteria, say, for science or for fun? This is, surprisingly, surprisingly simple. All you need is agar culture medium, a few sterile Petri dishes, and bacteria!

Steps

Preparation of petri dishes

1. Prepare agar culture medium. Agar is a jelly-like substance used to grow cultures of bacteria. Made from red and brown algae, agar is an ideal medium for many different types of microorganisms. Sometimes other substances, such as sheep's blood, are added to the agar if the goal is to achieve more rapid growth of microorganisms.

   • The easiest way is to use powdered agar. You will need 1.2 grams (½ teaspoon) for each 10 cm petri dish.
   • In a heatproof container, dissolve the agar powder in 60 milliliters (¼ cup) of hot water. You understand, 60 ml is for one Petri dish. Calculate the proportion you need yourself.
   • Place the container of water and powder in the microwave and, after bringing the water to a boil, boil it for a minute. The main thing is that the agar solution does not “run away”.
   • The nutrient medium is considered ready when the powder has completely dissolved, and the liquid itself has become transparent.
   • Allow the culture medium to cool, then proceed to the next steps.

2. Prepare Petri dishes. You have probably seen them - small flat cups made of glass or transparent plastic. Petri dishes have two parts, upper and lower, and are inserted into each other, which serves to protect the culture of microorganisms from air and other potential sources of contamination, and also contain gases released by microorganisms during the growth phase.

   • Petri dishes must be sterile. Sterile! Otherwise, the results of the experiment on growing bacteria will go down the drain. If you buy Petri dishes, then they must be sold in hermetically sealed packaging (such dishes are pre-sterilized by cold method).
   • Take the cups out of the package and separate the halves. Very carefully pour the culture medium into the bottom half of the cup in a thin layer just covering the bottom.
   • Close the petri dish quickly to prevent airborne bacteria from entering the agar. Let the Petri dishes stand quietly for 30-120 minutes until the culture medium cools and hardens (the finished culture medium will resemble jelly).

3. Cool Petri dishes. If you do not plan to immediately colonize the bacteria in their new home, then Petri dishes must be placed in the refrigerator until their time comes.

   • Storing petri dishes in the refrigerator is a guarantee that the water won't evaporate (and bacteria are very fond of water). In addition, the culture medium will become a little harder in the cold, and this will prevent you from accidentally tearing it during the replanting of bacteria.
   • Store Petri dishes upside down in the refrigerator. This way, condensation will not accumulate on the lid, which will then drip back and spoil the nutrient medium.
   • Petri dishes with culture medium can be kept in the refrigerator for a couple of months. When it's their turn, take the cups out of the fridge and let them warm to room temperature.

   Growing bacteria

   1. Plant the culture of bacteria in a Petri dish. The agar is solid, the Petri dish is at room temperature - everything is ready to continue the experiment! What's next on the plan? That's right, replanting a culture of bacteria in a nutrient medium! And there are two methods - either direct contact or sampling.

      • Direct contact: in this case, the bacteria enter the agar through ... yes, through direct contact with it. One of the most common methods of replanting in this way is to simply lightly touch the surface of the culture medium with your finger (before or after washing your hands, it doesn't matter). Alternatively, you can touch with a fingernail or even an old coin. You can simply place a hair on a nutrient medium or drop a drop of milk there. In general, use your imagination!
      • Sampling: This method will allow you to take samples of microorganisms from any surface and transfer them to a culture medium. All you need is cotton swabs. Just move the stick where you want to take a sample of microflora (even from the mouth, even from the keyboard), then run the same end of the stick over the surface of the nutrient medium (do not tear it). In a couple of days you will see interesting and terrible results of your experiment!
      • Alternatively, microorganisms from different sources can be planted in a Petri dish - for this, you just need to divide the dish into quarters.
      • At the same time, we recommend leaving one quarter without microorganisms - as a control group. This way you will be able to know if the agar was contaminated prior to the introduction of the bacterial samples.

   2. Close, label and seal the Petri dishes. After you place the bacteria in the culture medium, you need to close the cup with a lid and seal it with something like tape.

      • Be sure to sign what and where it grows in each particular cup, otherwise you won’t remember later. You can write with a marker.
      • As an extra precaution, you can store each cup in its own ziplock bag. This will provide an extra layer of protection for growing bacteria. If the package is transparent, then this will not prevent you from looking at the results.

   3. Place the Petri dishes in a warm and dark place. Let's say for a few days, so that the bacteria can safely grow. And do not forget that Petri dishes should also be stored upside down so that random drops of condensate falling from the lid do not spoil the beauty of the colony of microorganisms.

      • The optimum temperature for this stage is somewhere between 20-37°C. However, if it is necessary that microorganisms grow more slowly, then they can always be rearranged to a cooler place.
      • Allow the bacteria a minimum of 4-6 days to grow. During this time, the culture will develop quite well. The fact that the growth has begun, you will be informed by the characteristic smell coming from the Petri dishes.

   4. Record your results. After a few days, you will notice that in each Petri dish something of its own is thickly spiked - bacteria, mold, fungi, and so on.

      • Write down your observations of each cup, draw conclusions about where the most bacteria were.
      • What's in your mouth? And on the doorknob? And on the keyboard? Oh, the results will amaze you...
      • Using a special marker, you can track the growth rate of bacteria by drawing the contours of the culture daily on the bottom of the Petri dish. After a few days, the bottom will look like a cut of a tree - all in circles!

   5. Check the effectiveness of antibacterial agents. It will be interesting to see what happens if something antibacterial (soap, for example) is added to the bacterial culture. How effective will it be?

      • With a cotton swab, place a drop of something antibacterial in the center, then continue the experiment as usual.
      • The bacteria in the cup will grow, forming a ring around the area where the antibacterial agent was applied. There will be no bacteria there, this is the so-called "dead zone".
      • The effectiveness of antibacterial substances can be compared by evaluating the width of the dead zone in different Petri dishes. The principle is simple: the wider the zone, the more effective the substance.

In 1887, Julius Petri invented a simple pair of nesting dishes ideal for keeping samples of growing bacteria sterile - " Petri dish ».

Science historian Howard Markel tells the story of this ubiquitous laboratory supply, as well as the compelling discovery of the material in it, agar.

Shakespeare remarked, "Some are born great, some achieve greatness, and some put greatness on them." The last article of this famous axiom perfectly describes the only scientific achievement of Julius Richard Petrie (1852-1921).

In 1877, while still a young German military doctor, Petri was assigned to work for Dr. Robert Koch at the Imperial Health Department in Berlin. Koch, of course, was the Kaiser of bacteriology and was world famous for his work in helping to establish the theory of germ disease as accepted scientific fact. Petri's two-year post under Koch was a great success.

But to herald his astounding results on a myriad of infectious diseases, Koch had to grow bacteria, many of them. And so he and his assistants focused on creating the most reliable, clean lab methods.

The biggest problem they faced was contamination of their crops with airborne bacteria. One early approach involved growing bacterial colonies on a flat plate containing gelatin growth medium. The plate was then stored in a heavy glass-lined container to prevent melting microbes from depositing onto the plate and multiplying. But this method was too clumsy, especially when trying to observe the colonies through a microscope.

Appearance of Julius Petri. Influenced by his post at Koch's discovery factory, he fiddled with glassware, and in 1887 the landmark document "A Slight Modification of Koch's Coating Technique" appeared. This title is a bit of an understatement. Petri's 300-word paper describes the now familiar straight-sided round glass plate that contains the culture medium along with a similar shape of slightly wider diameter.

It was simple, practical and brilliant. The Petri plate not only prevented the penetration of microbes into the body, but was also flat enough to be easily viewed under a microscope for quantitative and morphological analysis.

Incidentally, it was Fanny Hesse, the wife of another Koch assistant, who suggested a much better culture substrate than gelatin: agar-agar, the Malay term for a polysaccharide derived from the seaweed red algae, or crimson. Ms. Hesse used the material when she made her summer fruit jellies. In 1881, she convinced her husband Walter that the agar would not melt under the incubation heat, the most diseased bacteria should thrive. This algae oil has become an ideal assistant for Petri dishes although we rarely remember Fanny's name today.

Dr. Petri continued to run the tuberculosis sanatorium. He did his clinical rounds in full garb of a Prussian army doctor's uniform. His uniform included a scarlet red sash wrapped around his painfully obese waist. Some ridiculed him as a control freak that looked like a three-dimensional map of the equator that revolved around the globe.

Does not matter. The good appointment of a doctor to Koch's laboratory may have been good luck. But his assessment of history is undeniable. A push into the crucible of discovery, he appeared with a dish commonly recognized as "

pure cultures

In 1872, Robert Koch, the future great microbiologist, was appointed health officer in Wolstein (now Wolsztyn in Poland), where anthrax was rampant at that time. This disease has been known since antiquity under the name "sacred fire": people believed that only angry gods could send such punishment to the earth. Anthrax was a threat to all agriculture - livestock most often fell ill. However, not only animals died, but also people: farmers, shepherds, milkmaids.

Examining the blood of dead animals under a microscope, Koch discovered that only one microbe, the bacillus, was to blame for the development of the disease ( Bacillus anthracis). The scientist was able to isolate the bacillus and grow pure culture- a culture represented by one type of microbes. He infected a perfectly healthy animal with a pure culture, giving it anthrax. The scientist realized that the creation of pure cultures is the key to successful determination of the causes of infection.

Robert Koch, like his predecessors, grew bacteria in a liquid medium - meat or grain broths. Koch managed to obtain a pure culture of anthrax bacillus in liquid broth, but he was looking for another method. There were good reasons for this. If several types of bacteria got into the broth, they mixed with each other and it was extremely difficult to separate them. I had to transplant bacteria more than once. From the solution, where the necessary bacteria were the most, Koch took a small drop and transferred it to a fresh broth. There were already fewer foreign bacteria in the new broth, but this operation had to be monotonously repeated several times, so that as a result only one type of microbes appeared in the nutrient medium.

Robert Koch(1843–1910) German microbiologist. He discovered anthrax bacillus, vibrio cholerae and tuberculosis bacillus (Koch's bacillus). In 1905 he was awarded the Nobel Prize in Physiology or Medicine "for research and discoveries concerning the treatment of tuberculosis."

Before Robert Koch, researchers observed microorganisms as colorless, which led to numerous errors. Koch used aniline dyes that selectively stain only microbes. After Koch's experiments, scientists around the world began to invent methods for staining bacteria. So, in 1884, the doctor Hans Christian Gram came up with a staining method that became one of the main methods for determining the presence and type of bacteria in a particular substrate.

Why are pure cultures needed?

Microbes are very small (on average 0.5-5 microns), do not differ much in appearance, which causes certain difficulties in their study. For research, it is necessary to isolate a microbe from the surrounding world, full of a variety of microorganisms. A microbial cell, once on a nutrient medium, gives offspring - a clot of identical cells, a colony that can be studied as a single microorganism. It turned out that, by choosing the cultivation conditions, it is possible to obtain pure cells of any microorganism. And that means giving it a name, describing its properties, classifying it. Thanks to this discovery by Robert Koch, microbiology was singled out as an independent science.

solid medium

After the report on the discovery of the causative agent of anthrax, Robert Koch was invited to head the laboratory at the microbiological institute in Berlin and was offered the position of adviser to the Ministry of Health. Koch had good equipment, talented assistants and the opportunity to solve a riddle that had tormented him for a long time. It was known that tuberculosis also causes some kind of microbe: it was possible to infect healthy animals with the tissues of a sick person. Koch managed to pick up a technique for staining tissue preparations in order to see the pathogen bacteria under a microscope. But his joy was short-lived - the bacterium did not want to grow on ordinary nutrient media.

Macro shot of tubercle bacillus colonies ( Mycobacterium tuberculosis). They are distinguished by a colorless uneven surface.

Once a scientist noticed a moldy potato thrown on the table with an abundance of multi-colored specks-colonies - gray, yellow, green. He collected samples from each colony and saw under the microscope that each speck is a colony of one type of microbe! In a liquid medium, the microbes mixed and it was extremely difficult to separate them. And on a solid medium, they remained in one place, multiplied and gave a pure culture!

Koch's accidental observation made a revolution: fresh potatoes became one of the first solid media for growing microorganisms. However, such a nutrient substrate is not suitable for all microbes, so the search for an alternative solid medium continued.

Koch again diligently began to grow tuberculosis culture. The bacterium did not grow on potato slices. Then he began to use gelatin to turn the broth into a solid nutrient medium. After many unsuccessful attempts, Koch added blood serum to the medium in order to recreate the conditions of a living organism. After 15 days (an unusually long time for the anthrax bacillus), droplets of colonies of the dangerous tubercle bacillus appeared on the surface of the medium.

Microorganisms divide every 20 minutes, so already 3 hours after transplanting microbes on a Petri dish, you can see colonies, and a day later the number of bacteria in them is in the millions.

microbiological art

Alexander Fleming came up with a new art form - drawing bacteria on a solid medium. Fleming, as a member of the Chelsea Art Club, invented amateur watercolors. The scientist painted graceful ballerinas, luxurious houses, soldiers with bacteria. The creation of the picture required accuracy: it was necessary not only to find bacteria with different pigments, but also to choose the growing time so that the same colors would grow at the same time and not violate the color boundaries.

The American Society for Microbiology (ASM), inspired by the example of Fleming and his colleagues, has been holding the Agar Art Competition since 2015. Talented microbiologists and artists paint real pictures. Some come up with their own stories, others reproduce the paintings of the masters, for example, Van Gogh's Starry Night.

In 1928, the British bacteriologist Alexander Fleming discovered that a colony of mold fungi had grown next to bacteria on agar in one of the Petri dishes. The bacterial colonies around the mold turned pale - their cells were destroyed. Fleming isolated from mold fungi a substance that destroys bacterial cells - penicillin, the first antibiotic. Fleming's discovery changed not only medical science, but also the fate of many seemingly hopeless patients.

Talented laboratory assistant

At that time, the only laboratory bottle that was suitable for growing microbes was a test tube. But handling it required skill: if you put the test tube horizontally, the unsolidified medium will spill, if you put it at an angle, it can fall and break. The chance of contracting a dangerous disease multiplied before our eyes! Then Koch and his laboratory assistants came up with the idea of ​​pouring the nutrient medium into cups and covering them with tall glass caps. But to look at the colonies, the cap had to be removed, and this is a direct route of infection. It was then that the finest hour of one of the laboratory assistants came - Julius Petri. He reduced the height of the walls of the cup in which the microbes were grown, leaving low sides. And instead of a huge cap, he covered it with another transparent cup - it turned out to be more convenient to observe the colonies.

Petrie worked under Koch for only a couple of years (1877–1879), but during that time he had a profound effect on the future of microbiology. The innovation of Julius Petri gave a strong impetus to medicine and saved millions of lives. After working under Robert Koch, he headed the Gobersdorf sanatorium, the first European center for the treatment of tuberculosis patients.

agar agar

In Koch's laboratory, not only a Petri dish appeared, but also a standard filling for it - an agar nutrient medium. Its predecessor, a medium containing gelatin, melted easily when heated, like jelly put in a warm place. Colonies on such a medium turned into mush.

Agar-based medium invented Walter Hesse, another laboratory assistant of Koch. He entered the service along with his wife Fanny. She was not listed as an employee of the laboratory, but she did the work of a scientific illustrator - she sketched the microorganisms that she saw under a microscope.

One day Fanny made jelly. Hesse noticed that it does not melt in the sun and retains its shape. He found out that the main component of jelly is agar-agar, a substance that is extracted from red and brown algae. Walter replaced the standard gelatin with it, and the bacterial culture media became harder. Agar-agar is still used today for the preparation of media, but it is purified in a special way.

To determine the effectiveness of antibiotics in the pharmaceutical industry, special tests are used. For example, the agar diffusion method. Microorganisms are inoculated into Petri dishes. Disks containing certain doses of different antibiotics are placed on the seeded surface at an equal distance from each other. The larger the radius of the growth inhibition zone, the more effective the drug against this microorganism.

At first, the Petri dish was used only for growing cell cultures, but now these dishes are used in various fields of science. For example, Petri dishes are used to study the effectiveness of antibiotics, they are used to study food safety and grow genetically engineered bacteria that synthesize the insulin necessary for diabetics.

Petri dishes are made in different sizes and from a variety of materials - glass, plastic and even stainless steel. For work, the scientist can choose the right one.

Modifications

The Petri dish is usually made of clear glass or plastic (clear polystyrene) and comes in a variety of sizes. The most commonly used options have a diameter of about 50-100 mm and a height of about 15 mm.

Application

The cup is widely used in microbiology for culturing colonies of microorganisms. To do this, it is filled with a layer of nutrient medium, on which the culture of microorganisms is sown.

Glass dishes are reusable but require sterilization before re-inoculation. Cups made of plastic materials are supplied sterile, in sealed packaging.

In addition, the Petri dish is often used for applied purposes, such as evaporating liquids, storing small fragments of various preparations, dissecting small animals and plants, and etching small printed circuit boards.

Often, Petri dishes are used in terrariums for a “nesting base” when breeding amphibians (dart frogs, leaf climbers and other animals).

see also

View this template Chemical laboratory equipment Glassware Separation equipment Measuring Various equipment Security

Write a review on the article "Petri Dish"

An excerpt characterizing the Petri dish

- I told you - this cave is evil! .. I told ... I told you! - convulsively sobbing, the kid lamented - Well, why didn’t you listen to me! And what should I do now?.. Where should I go now?..
Tears flowed down dirty cheeks in a burning stream, tearing apart a small heart... Beloyar didn't know if his beloved grandfather was still alive... Didn't know if the evil people would come back? He was just scared as hell. And there was no one to comfort him... no one to protect him...
And Svetodar lay motionless at the very bottom of a deep crack. His wide-open, clear blue eyes, seeing nothing, looked at the sky. He went far, far away, where Magdalena was waiting for him... and his beloved father with kind Radan... and sister Vesta... and his gentle, affectionate Margarita with her daughter Maria... and unfamiliar granddaughter Tara... And all- all those who died long ago defending their native and beloved world from non-humans who called themselves humans...
And here, on the ground, in a lonely empty cave, on a round pebble, hunched over, a man was sitting... He looked quite small. And very scared. Bitterly, weeping angrily, he furiously rubbed his evil tears with his fists and swore in his childish soul that such a day would come when he would grow up, and then he would certainly correct the “wrong” world of adults ... Make it joyful and good! This little man was Beloyar... a great descendant of Radomir and Magdalena. Small, lost in the world of big people, crying Man...

Everything I heard from the lips of the North once again flooded my heart with sadness ... I asked myself again and again - are all these irreparable losses really natural? .. Is there really no way to rid the world of evil spirits and malice ?!. All this terrible machine of global killing made the blood run cold, leaving no hope of salvation. But at the same time, a powerful stream of life-giving force flowed from somewhere into my wounded soul, opening every cell in it, every breath to fight against traitors, cowards and scoundrels! .. With those who killed the pure and brave, without hesitation, by any means, if only to destroy everyone who could be dangerous for them ...