Practical Bacteriology�Laboratory Five

Types of Culture media

How is media made?

• When lab personnel make media they measure out a quantity of dry powdered nutrient media, add water and check the pH.

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• They pour the media into bottles, cap it and autoclave.

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• This is a process similar to home canning techniques in food preservation.

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• The autoclave exposes the media to high temperature (121°C) and pressure (15 psi) for 20 minutes.

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• Once the media is autoclaved it is considered ______ (all life forms killed).

Image: Autoclave, Astell Scientific; Pressure cooker, Rama

From the Virtual Microbiology Classroom on ScienceProfOnline.com

Classification of culture media on the basis of consistency

1. Liquid or broth (without agar)
2. Semi solid media 0.5% agar (used for testing motility)
3. Solid media (gelatinous) 1.5-2% agar

Classification based on functional use or application

1. Basal media
2. Enriched media
3. Enrichment media

4. Differential media
• Blood agar plate
1. Beta – haemolytic
2. Alpha – haemolytic
3. Gamma haemolytic (Non – haemolytic)
• MacConkey agar

5. Selective and selective – differential media
• MacConkey agar
• Mannitol salt agar
6. Transport media
7. The Preservation Culture media