AIM: To prepare the Nutrient Agar (solid) and Nutrient Broth (Liquid) medium

Principle: A growth medium or culture medium is a solid or liquid or semi-solid designed to support the growth of microorganisms or cells. The culture media are devised in such a way that the organisms should get all the nutritional requirements. Nutrient media contain all the elements that most bacteria needed for growth and are not selective, so they are used for the general cultivation and maintenance of bacteria kept in laboratory culture collections. In Nutrient media carbon source is glucose, beef extract as a source of mineral salts, nitrogen, vitamins and peptone is semi digested protein. Nutrient Broth medium is generally used for cultivation of Bacteria. When a broth medium is supplemented with agar- agar, it is called agar medium, for example nutrient agar medium (NAM) for cultivation of bacteria. Agar- agar is also called simply agar. Agar is product of marine red algae such as Gelidium and Gracilaria.

Requirements Nutrient Broth medium powder Nutrient Agar medium powder Distilled water 500 ml Conical Flask Cotton plug

Composition of Nutrient Broth Peptic Digest of animal tissue: 5 gm Sodium chloride: 5 gm Beef Extract: 1.5 gm Yeast Extract: 1.5gm Distilled Water: upto 1000 ml

Composition of Nutrient Agar Peptic Digest of animal tissue: 5 gm Sodium chloride: 5 gm Beef Extract: 1.5 gm Yeast Extract: 1.5gm Agar: 15gm Distilled Water: upto 1000 ml

Procedure: A. Preparation of Nutrient Broth (Liquid medium): 100ml Weigh 1.3 gram of nutrient broth powder and put it in a conical flask with a cotton plug. Measure 100 ml of distilled water in a measuring cylinder and add in to conical flask containing nutrient broth powder. Dissolve the nutrient broth powder in the water by swirling. Autoclave it at 15 psi pressure in autoclave.

B. Preparation of Nutrient Agar ( Solid medium): 100ml Weigh 2.8 gram of nutrient agar powder and put it in a conical flask with a cotton plug. Measure 100 ml of distilled water in a measuring cylinder and add in to conical flask containing nutrient agar powder. Dissolve the nutrient agar powder in the water by swirling. Autoclave it at 15 psi pressure in autoclave.

Precautions: 1. Always use the distilled water for making the media. 2. All the glassware should be properly sterilized.