According to the nutrient composition of the medium, it can be divided into following types of medium in microbiology laboratory: basic medium, complete medium and supplementary medium，etc. Such terms are mainly used in microbial genetics.
(1) Basic medium. It is also known as "minimum medium". It can only ensure the normal growth of wild-type strains of some microorganisms, and it is a synthetic medium with the lowest nutrient requirements, commonly expressed as "[-]". This kind of medium often lacks some growth factors, so the mutated nutrition deficient strain can not grow.
(2) Complete medium. If some natural substances (such as yeast extract, peptone, etc.) rich in chloro acid, vitamin and base are added to the basic medium, the growth factor is added to form a complete medium. Complete culture medium can be used to meet the growth needs of various nutrient deficient strains of microorganisms, often expressed as "[+]".
(3) Supplement medium. If one or several nutrients are added to the basic culture medium to meet the needs of the growth of the corresponding auxotrophic strains, this culture medium is called supplementary culture medium, which is commonly expressed as "[A]", "[B]".