The culture medium is classified by morphology
According to their different physical states, culture media can be divided into four categories: liquid, fluid, semi-solid and solid. The physical state of culture media depends on whether coagulant is added to the culture media or the amount of coagulant added.
1. Liquid nutrient medium is a medium that exists in complete liquid state at normal temperature without any coagulant, such as broth medium or general liquid enrichment medium.
2. Semi liquid medium: add 0.05% ~ 0.1% agar powder into the liquid medium to make it have a certain viscosity, which is the fluid medium. The addition of agar powder increases the viscosity of the culture medium, reduces the speed of oxygen in the air entering the culture medium, enables the culture medium to maintain anaerobic conditions for a long time, and is conducive to the growth and propagation of general anaerobic bacteria, such as thioglycolate medium and improved Martin medium. A small amount of agar can be added to the liquid culture medium generally used for the inspection of mold and anaerobic bacteria to make it a fluid culture.
3. Half solid medium is made by adding 0.2% ~ 0.5% agar powder into the liquid medium, heating and dissolving, and then cooling. It is suitable to be inverted and in the softest state. It is generally used for bacterial dynamic test, strain passage, storage and transportation of samples.
4. Solid medium: the medium contains sufficient coagulant (agar powder > 0.5%), which can maintain a solid state at normal temperature. Most of these media are used for microbial isolation, purification, drug sensitivity test and vaccine manufacturing. Such as nutrient agar, nutrient slope, SS Agar, TCBS agar, etc. In addition, there are also some special-purpose culture media, such as Lv's serum slant culture media and egg slant culture media prepared with serum or eggs as coagulants.