Nutrient Medium Bile

Bile nutrient medium is a selective nutrient medium containing bile as an inhibitor of the growth of certain microorganisms.

Bile contains bile acids and salts that inhibit the growth of many bacteria. However, some microorganisms, such as Escherichia coli, are resistant to the inhibitory effects of bile. Therefore, the addition of bile to the nutrient medium allows the selective cultivation of bile-resistant bacteria.

Bile culture media are widely used in microbiological practice for the isolation and identification of Escherichia coli and other members of the Enterobacteriaceae family. A classic example is Endo agar, which contains bile salts and lactose. On this medium, E. coli forms characteristic metallic shiny colonies with a greenish tint.

Thus, due to the presence of bile, bile nutrient media make it possible to isolate and identify certain groups of microorganisms that are resistant to its inhibitory effect. This makes such media an important tool for microbiological research.

Nutrient medium Bile is a selective nutrient medium that contains bile. It is widely used in microbiological practice for the cultivation and detection of pathogenic microorganisms, such as Escherichia coli, Salmonella, and Mycobacterium tuberculosis.

The microbiological environment must have the same structure as human biological objects (organism). An acidic reaction of the environment is a necessary condition for the proliferation of microorganisms. Acidic nutrient media are prepared on the basis of peptone hydrolyzate with the addition of glucose or yeast extract. Liquid hydrolyzate media of the following composition (g/l) are also used: - yeast autolysate – 2; – casein hydroxide – 5; – cheese casein – 4; – disodium phosphate – 3; – disubstituted sodium citrate – 7; – magnesium sulfate – 0.5-2.0; – acidity up to 7.4±0.2 (environment pH 6.8-7.2), carbon dioxide concentration – 1%. A distinctive feature of liquid media is their turbidity due to the action of microflora on them and the formation of their metabolic products. Pollution of the environment, causing the formation of turbidity, worsens the growth conditions of microorganisms, and complicates the selection of pure crops. Therefore, when placing small portions of inoculum on a nutrient medium, it is possible to accelerate the growth of the test tube, since the conglomerates decompose. It is possible to accelerate the growth of bacteria during the fermentation process of the medium. One example of this method of isolating pure cultures is growing bacteria on a medium containing vegetable waste. To study the species of the isolated culture, enzyme activity is determined, which, firstly, is characteristic only of a certain species and, secondly, depends on the composition of the culture medium. For this purpose, strains of bacteria are grown in a liquid medium - a test tube with a column in it is filtered through a large one.