Bacterial culture is a directed and controlled technique for the growth of bacterial colonies, in order to facilitate its study.
Often, the study of the morphology, arrangement and interpretation of staining properties is not sufficient to identify the bacterial agent and, for this reason, researchers in some branches of biology turn to culture, with the aim of improving the performance of the processes involved , studying the cultural characteristics of the bacteria such as the ability to grow in a selective medium.
Microbiology and molecular biology often use bacterial culture techniques.
In order to carry out a bacterial culture, an inoculum and a culture medium are required. The growth of microorganisms in different culture media will provide the first information for their identification. The growth potential of each culture medium must be known, making it possible to adapt to the expected bacterial profile for each material.
The culture medium consists of a liquid or gelled substance, simple or complex, which allows nutrition, growth and multiplication of microorganisms. Some procedures are essential when preparing each culture medium, in order to obtain better results and avoid contamination.
Culture media can be classified according to their physical state, composition and use. As regards their physical state, the media can be liquid or gelled; in relation to the composition of the medium, they can be classified as natural, synthetic and semi-synthetic. In relation to their laboratory practice, one can consider the basic means, the enriched means and the selective means.
The gelled media allows the growth of cells forming colonies and is obtained from a liquid medium to which is added a gelling substance that, in the beginning, was gelatin, but became agar.
Bacterial culture uses different types of agar gel, each of which has a specificity. Check out the characteristics of some of them below:
Nutrient agar (AN)
It is a relatively simple and widely used means in the microbiology laboratory procedures. Its purposes include the analysis of water, food and milk as a means for preliminary cultivation of samples submitted to bacteriological tests.
Blood agar (AS)
The medium offers excellent growth conditions for most microorganisms. Among its purposes are the isolation of non-tedious microorganisms and verification of hemolysis of Streptococcus spp . and Staphylococcus spp.