Bacterial culture media can be classified into three types according to their composition: synthetic, natural, and semi-synthetic.
Synthetic culture media. The components of synthetic culture media are completely made up of known chemical substances. The chemical composition of this type of culture media is clear, the composition is precise, and it is highly repeatable. However, synthetic culture media is more expensive and microorganisms grow slower in this type of culture media. Examples of synthetic culture media are the No. 1 Koch medium and Schatz medium.
Natural culture media. Natural culture media are made from natural substances, such as boiled potatoes and common beef broth, which are used to culture fungi and bacteria, respectively. The chemical composition of this type of culture media is very unstable and difficult to determine. However, these culture media are easy to prepare, nutritious, and are commonly used.
Semi-synthetic culture media. Semi-synthetic culture media include adding known inorganic salts to natural organic substances or adding certain natural substances to synthetic culture media, such as the potato glucose agar based medium used for fungal culture. This type of culture media can more effectively meet the nutritional needs of microorganisms.
Bacterial culture media can be classified into three types based on their physical state: solid, liquid, and semi-solid culture media.
Solid culture media. Solid culture media are made by adding a gelling agent, such as agar, gelatin, or silica gel, to the culture media. Solid culture media are commonly used for microbial isolation, identification, counting, and strain preservation.
Liquid culture media. Liquid culture media do not contain any gelling agents. This type of culture media has uniform components, and microorganisms can fully contact and utilize the nutrients in the culture media. It is suitable for studies on microbial physiology, and has a high fermentation rate and is easy to operate, making it commonly used in the fermentation industry.
Semi-solid culture media. Semi-solid culture media are made by adding a small amount of gelling agent to liquid culture media to form a semi-solid state. It can be used for observing bacterial movement, identifying bacterial strains, and measuring the efficacy of phages.
Medium used for bacterial culture can be classified into bacteriological media, actinomycete culture media, yeast culture media, and fungal culture media based on microbial types.
Commonly used bacteriological media include nutrient broth and nutrient agar culture media; the commonly used actinomycete culture medium is the No.1 Koch medium; the commonly used yeast culture media include potato sucrose culture medium and malt extract culture medium; the commonly used fungal culture media include potato sucrose culture medium, bean sprout juice glucose (or sucrose) agar culture medium, and Schatz culture medium.
Bacterial culture media can be classified into enriched culture media, selective culture media, and differential culture media based on their special applications.
Enriched culture media. Enriched culture media are made by adding blood, serum, or extracts of animal or plant tissues to the culture media, and are used to culture some demanding microorganisms.
Selective culture media. Selective culture media are designed based on the special nutritional requirements or physical and chemical resistances of a certain type or class of microorganisms. These culture media can separate the required microorganisms from mixed microorganisms.
Differential culture media. Differential culture media are made by adding certain reagents or chemical agents to the culture media, causing certain changes after cultivation, thus distinguishing different types of microorganisms.