Dalia Kamal Eldien Mohammed Culture media Dalia Kamal Eldien Mohammed practical NO (2)

Culture media Whatever a particular mould needs, it must always be supplied with some form of organic carbon for energy, a source of nitrogen for protein and vitamin synthesis, and several minerals. The substance on which a mould is grown in the laboratory is called a medium  Culture media can be solid or liquid, depending on the sort of information one wishes to obtain. For the purposes of identification, solid culture media are usually more useful, as they allow the mould to sporulate more easily.

Culture media The selection of media depends on the organism if it is fastidious or non fastidious The non fastidious fungi cultured on simple media e.g Sabouraud’s dextrose Agar or mycosel agar Addition of chloramphenicol or mixture of penicillin and streptomycin to inhibit the bacterial growth Addition of cyclohexamide(actide) inhibit the saprophytic fungi Fastidious fungi need enriched media e.g brain heart infusion

Common media used in mycology lab Sabouraud’s dextrose Agar Sabouraud Dextrose Broth Yeast Extract Peptone Dextrose (YEPD) Malt Extract Agar Cornmeal Agar : is used for the cultivation of fungi and the demonstration of chlamydospore production. Potato Dextrose Agar (PDA) Brain heart infusion (fluid& slope)

Preparation of media The culture media are commercially available i.e ready made The steps of preparation:- Weight the dehydrated powder according to formula given by manufacture company Most culture media are prepared by dissolving the necessary nutrients in water, to obtain a balanced solution supplying everything the mould needs for growth. Preparation of solid media involves dissolving a solidifying agent in the solution by heat, that will harden to a gel upon cooling.

Pouring this step be before sterilization if we use unsterile bottle or tube Sterilization according to the manufacture company , but generally sterilize by autoclave Preservation Usually we use slope media in bottle or tube with screw to avoid the drying and contamination because of long incubation needed

Steps of preparation

Example Sabouraud’s Agar : is used in the cultivation of pathogenic and commensal fungi and yeasts. It consists of a mixture of dextrose and peptone at a 2:1 ratio.

Example to formula Difco™ Sabouraud Brain Heart Infusion Agar Base Approximate Formula* Per Liter Brain Heart Digest ......................................... 9.25 g Proteose Peptone ............................................ 5.0 g Enzymatic Digest of Casein ............................. 5.0 g Dextrose ..........................................................21.0 g Sodium Chloride ............................................ 2.5 g Disodium Phosphate ...................................... 1.25 g Agar .................................................................15.0 g *Adjusted and/or supplemented as required to meet performance criteria.

Dehydrated media

Dehydrated Product of SDA 1. Suspend 59 g of the powder in 1 L of purified water. Mix thoroughly. 2. Heat with frequent agitation and boil for 1 minute to completely dissolve the powder. 3. Autoclave at 121°C for 15 minutes. Cool to 50-55°C. 4. Aseptically add 1 mL chloramphenicol solution (100 mg/mL) 5. Test samples of the finished product for performance using stable, typical control cultures.