How to make the work of the petri dish contest, and how to make the plate medium

1.Preparation of raw materials: The raw materials for making petri dishes are mainly glass, plastic, etc.

Glass dishes are usually made of borosilicate glass, while plastic dishes are made of materials such as polystyrene or polycarbonate. In addition, it is also necessary to prepare auxiliary materials such as quartz sand, sodium carbonate, and calcium carbonate.

2.Production steps: First, the borosilicate glass is ground into powder, and then auxiliary materials such as quartz sand, sodium carbonate, and calcium carbonate are added, mixed evenly and placed in the furnace for firing.

After the firing is completed, the glass blank is cut into a petri dish of the required size, and then polished, cleaned and other processes to finally make a finished product.

Isolation and culture of microorganisms are inseparable from solid media. In microbiology labs, the use of solid media is so frequent and routine that this method seems like a no-brainer.

However, back in 1881, before the advent of solid media, the cultivation of microorganisms could only be carried out in liquid media. In order to be able to directly observe the morphology and growth of the culture, scientists want to grow microorganisms on solid surfaces, just as microorganisms grow on orange peels or potatoes. Robert Koch (1843-1910), a German physician, used boiled and sterilized potatoes to grow bacteria.

After that, he experimented with using gelatin as a coagulant for the medium. He added gelatin to a liquid medium to thaw it, and then slowly poured the evenly mixed liquid onto the surface of a glass plate. When the gelatin cools and solidifies, a solid medium forms on the surface of the glass plate.

To prevent contamination by germs in the air, Koch also used a glass cover to isolate the glass panes from the surrounding environment. However, it was soon discovered that gelatin softened at more than 20 years old, making it difficult to strip to isolate microorganisms. Gelatin liquefies at temperatures above 25, and most bacteria are incubated at temperatures below 25.

First, you need to have a petri dish. Do you make a copycat version yourself? Why has no one gone to the cottage for Koch's petri dishes? Because there's nothing to replace it.

It is then sterilized by autoclave. Then it is to make the medium, choose different media according to the microorganisms you want to cultivate, and the recipe can be checked.

Finally, pour the plate while the medium is in a liquid state.

The nutrient solution is prepared according to the nutrients required by the microorganisms to be cultured, as well as agar.

The easiest way, hehe, you can mash potatoes, or add grams of agar per 100ml of liquid in broth, put all of them into an Erlenmeyer flask, seal them with double-layer kraft paper, and sterilize them in a pressure cooker.

This is the easiest way to do it. If possible, you can replace potatoes with beef extracts, peptones, etc., broth :)

A steamed bun, scattered water is almost the same;

It should be 1 5 3 2 4

Because Wu Gai 5 and Wheel Orange Sleepy Lanian 3 are reversed, the petri dish is not sterilized, and the culture process is easy to be confected. Thank you!

Plating medium.

Here's how to make it:

Wash and dry the Petri dish so that the direction of the lid of each Petri dish is the same, and use kraft paper.

Wrap it or place it in a special tin can with the direction of the lid indicated. Autoclave or dry sterilize and set aside.

Take the medium that has not yet solidified after sterilization and place it in a sterile box or clean bench.

Inside, slightly open the lid of the sterilized Petri dish (expose a small slit), pour in the medium (the thickness is, cap, condense, inverted and set aside.

(1) Nutrient composition of culture medium: all kinds of culture media generally contain water, carbon source, nitrogen source and inorganic salt. It is divided into liquid medium and solid medium.

Methods for preparing beef paste peptone solid medium: calculate, weigh, dissolve, sterilize, and pour plates.

2) Common disinfection methods: boiling sterilization, ultraviolet irradiation, pasteurization and chemical disinfection.

3) Common sterilization methods: burn sterilization, dry heat sterilization and autoclave sterilization.

The sterilization and disinfection methods used for culture medium, petri dish, inoculation loop, experimental operator's hands, air, and milk are in order: autoclave sterilization, dry heat sterilization, burn sterilization, chemical disinfection, ultraviolet sterilization, pasteurization.

4) Preparation of plate medium: calculation, weighing, melting, sterilization, and pouring plates.

5) Inoculation method: plate scribing method and dilution coating method.

The method of pouring the plate: hold the test tube or triangular bottle containing the medium in the right hand next to the flame, gently pull out the test tube stopper or cork with the left hand, and keep the mouth of the test tube or bottle facing the flame; Then use the edge of the palm of your right hand or the little finger and ring finger to clamp the tube (bottle stopper or stopper can also be placed on the edge of your left hand or between your little finger and ring finger). If the medium in the tube or triangular flask is used up at one time, the tube stopper or stopper does not have to be clamped in the hand).

Take the Petri dish in your left hand and open the lid near the flame, quickly insert about 15ml of the medium, gently shake the Petri dish after the cap, so that the medium is evenly distributed at the bottom of the Petri dish, and then placed flat on the table, and then it will be a plate after condensation.

Slab Scribing Operation:

Pick other bacteria-containing samples: select a flat and smooth inoculation loop, and pick a small number of strains according to the aseptic operation method.

Zone A: Place the plate upside down next to the gas (alcohol) lamp, take out the bottom of the dish with the left hand and try to make the plate perpendicular to the tabletop, with the medium facing the gas lamp (at this time, the lid of the dish is facing up, still remaining next to the gas lamp), and the right hand holds the inoculation loop and first divides 3-4 continuous parallel lines in the A area (the number of lines should be determined according to the amount of bacteria). After the A area is marked, the residual bacteria on the ring should be burned immediately, so as not to affect the separation effect of the subsequent areas due to too many bacteria.

When burning the inoculation ring, hold the bottom of the dish in your left hand and cover it over the lid (do not put it inside the lid) to prevent contamination by miscellaneous bacteria.

Distribution of bacteria and fungi Bacteria and fungi, which are microorganisms in nature, are invisible to our naked eyes and must be aided by certain instruments (microscopes), but they are everywhere. Before figuring out their distribution, we specially carried out **: 1. In the experiment, five sets of petri dishes should be selected for experimentation, one is used for comparison, and the other four are used to cultivate bacteria in different environments, and they are cultivated in different environments, so as to obtain the living conditions of bacteria and fungi.

2. The petri dishes used in the experiment should be sterilized at high temperature (ask students to think about why), and the petri dishes of each group should be cultivated under the same environmental conditions. This means preparing at least 5 sets of Petri dishes (for each group).Since comparing the presence of bacteria and fungi in different environments is a one-factor comparison, in addition to the location of sampling is a variable, the conditions under which the microbial culture is performed should be consistent (temperature, humidity, etc.).

3. After high temperature treatment, the spores of bacteria or fungi mixed in the petri dish and medium can be killed (it is impossible for bacteria and fungi to exist in the environment of strict high temperature sterilization), so as to exclude the pollution of other environments outside the experiment. Therefore, do not blindly open the petri dish before the experiment to prevent the spores of bacteria or fungi from falling on the medium, and the purpose of using sterile cotton swabs in the experiment is also to prevent microorganisms on the cotton swabs from contaminating the medium. That is, at the time of vaccination, it is necessary to pay attention to contamination.

4. The distribution of bacteria in different environments is not the same, so when collecting strains, we should pay attention to the selection of environment and achieve a certain representativeness. 5. The inoculated medium should be cultured under specific environmental conditions. (The control group was cultured in a certain environment, and the other four groups were cultured in four different environments, so that the living conditions of bacteria and fungi could be studied, and at the same time, we could also think about what methods we use in our lives to prevent contamination by bacteria and fungi; In particular, what is the standard for the hospital to judge.

6. When detecting bacteria and fungi in different environments, the members of each team should make a good division of labor to ensure that they are observed and recorded within the specified time. It also facilitates discussions among group members and between groups. (Analyze the living environment, distribution range, number and so on of bacteria and fungi).

Are you satisfied with the above?