Solid media Liquid media are solidified by the addition of, for example, agar, a long-chain carbohydrate which does not affect the nutrient properties of the original medium.

Microbiological media may be prepared as either liquid or as a solid media. When a solid medium is prepared, a corresponding liquid broth is solidified by the addition of agar to the broth. Agar is a polysaccharide found in the cell walls of some algae. It is inert, and degraded by very few microorganisms.

Agar is an ideal solidifying agent for microbiological media because of its melting properties and because it has no nutritive value for the vast majority of bacteria. Solid agar melts at about100°C; liquid agar solidifies at about 42°C.

Solid media is used for the isolation of bacteria as pure culture. ‘Agar’ is most commonly used to prepare solid media. Agar is polysaccharide extract obtained from seaweed.

How to prepare nutrient broth?

1. Add 13g of nutrient broth powder (CM0001B) in 1L of distilled water.
2. Mix and dissolve them completely.
3. Pour them into the final containers (eg. conical flask)
4. Sterilize by autoclaving at 121°C for 15 minutes.

Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms. Owing to the presence of certain dyes or chemicals in the media, the organisms will produce characteristic changes or growth patterns that are used for identification or differentiation.

This medium is both selective and differential. The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose.

Growth conditions: Temperature range: 4- 45°C (39-113°F); can survive refrigeration and freezing. Optimum Temperature: 37°C (98.6°F) pH range: can survive at pH 3.6.

Escherichia coli cells are typically 1.1–1.5 μm wide by 2–6 μm long and occur as single straight rods. They can be either motile or nonmotile, and when motile produce lateral, rather than polar flagella.

coli (STEC) infection vary for each person, but often include severe stomach cramps, diarrhea (often bloody), and vomiting. Some people may have a fever, which usually is not very high (less than 101˚F/38.5˚C). Most people get better within 5 to 7 days.