1. After the medium is prepared, it should be sterilized immediately to prevent the medium from being used by non-target microorganisms. General moist heat sterilization is 12 1 degree for 20 minutes. After sterilization, the culture medium is suitable to be placed at room temperature 1~2 days, and the liquid culture medium is not turbid, indicating sterility. 2. Natural culture medium contains all kinds of substances needed for microbial growth, so there is no need to add trace elements. Its advantages are rich nutrition and good culture effect, but its disadvantages are complex components and limited sources. 3. Water vapor has a strong penetrating power, which can quickly liquefy after entering microorganisms, and at the same time release a lot of energy to achieve the purpose of sterilization. However, dry heat sterilization can only transfer heat through air, and the heat transfer effect is poor, so the temperature of dry heat sterilization is high and the time is long. 4. Microorganisms in nature all grow in disproportionate substrates, and we prepare the culture medium according to a certain proportion according to the growth characteristics of the target microorganisms, in order to make the target microorganisms grow faster.