Petri dishes consist of a bottom and a lid. It is a chemical device used for culturing bacteria. Usually made of glass or plastic.
Because the lid of the bacterial culture dish can prevent microorganisms in the air from falling into it, the lid of the bacterial culture dish can only be partially opened except for the alcohol lamp during inoculation. It's also important to note that the Petri dish is upside-down, and the reason why it needs to be upside down is as follows:
1. Prevent the evaporation of water in the medium, especially when the medium is poured, if it is poured less, it is easier to dry up, affecting the growth of microorganisms.
2. Putting it upside down can prevent the colony from spreading to a certain extent, so that a single colony can be formed, which is convenient for counting. When the bottom is facing down, the water in the bacterial culture dish will evaporate, and when it rises to the lid, due to the low temperature, condensation often forms. , this condensate may drip, causing the individual colonies below to be confused together.
3. The water in the medium should evaporate to form water droplets. If the water droplets accumulate on the medium plane, it will affect the growth of the colony. Therefore, to ensure the dryness of the medium, the culture must be inverted.
4. This is the point of the bacterial culture dish, and it is easy to take, large and small, and will not be destroyed, and also prevent foreign objects from falling on the medium.