Principle of bacterial separation

Principle of strain separation: it is the process of separating the required bacteria from the mixed microbial population through aseptic operation.

The separation of culture medium and strains refers to the operation technology of obtaining pure microorganisms from samples containing many microorganisms. The separation of strains is mainly carried out on Petri dishes, and the commonly used methods are dilution method and streaking method. The purpose of using these two methods is that an individual of microorganism grows colonies visible to the naked eye on solid culture medium through propagation, and then according to the culture characteristics, the required strain is retrieved with an inoculation needle, and it is proved to be a single-shaped thallus under the microscope.

For example, the culture medium used to separate cellulolytic microorganisms is a culture medium with cellulose as the carbon source, because only cellulolytic microorganisms can grow from this culture medium.

Most bacteria and fungi are usually separated by plate method because most of them grow well on solid medium. However, so far, not all microorganisms can grow on solid media, such as some bacteria with large cells, many protozoa and algae. These microorganisms still need to be separated in liquid culture medium to obtain pure culture.

No culture medium or culture conditions can meet the needs of all microorganisms, and all cultures have certain selectivity. If the growth requirements of microorganisms are known, a specific environment suitable for the growth of microorganisms can also be designed, so that the microorganisms can be selectively cultivated from the mixed microbial population, although the microorganisms may be only a minority in the mixed microbial population. This pure culture technique of separating microorganisms by selective culture is called selective culture separation, which is especially suitable for separating and looking for useful microorganisms from nature.