When the dish cover is cultured upward, the water evaporated from the culture medium will condense on the dish cover and may fall on the surface of the culture medium, which will affect the culture results.
When the Petri dish is inverted, water evaporation will condense evenly on the surface of the culture medium, and evaporation and condensation will form a balance, which will not affect the culture results. This is the main reason.
Secondly, inversion will not only pick up the vegetable lid when picking it up. When holding a Petri dish upright, you can just pick up the lid and expose the culture medium to the air.
Extended data
Culture plate is the most commonly used form of solid culture medium to obtain pure cultures of microorganisms. It is a solid plane of culture medium formed after solid culture medium is cooled and solidified in a sterile Petri dish, which is often referred to as Petri dish for short. Also known as flat medium and flat medium.
Plate culture medium is often used to isolate a single spore, determine the growth rate of mycelium, observe the colony morphology, antagonistic experiment and determine the number of miscellaneous bacteria in inoculation space.
Artificial nutrient medium suitable for microbial growth and reproduction or accumulation of metabolites is called microbial medium in microbiology. Because various microorganisms have different requirements for nutrient substrates, there are many kinds of microbial media, and some compounds that cannot be synthesized by themselves can be added to different media according to actual needs.
Due to the different requirements of various microorganisms for nutrition and the different purposes of scientific research or the needs of production practice, there are many kinds of culture media. So far, there are thousands of different media.
According to the chemical composition of the medium, it can be divided into natural medium, synthetic medium and semi-synthetic medium.
According to its physical state, culture medium can be divided into solid culture medium, liquid culture medium and semi-solid culture medium.
References:
Types of Microbial Culture Media-Baidu Encyclopedia