Microbiological Media

Microbiological Media

1. Liquid (broth) vs. Semisolid Media

   • Liquid Medium
     • Components are dissolved in water and sterilized
   • Semisolid Medium
     • -A medium to which has been added a gelding agent -Agar -Gelatin -Silica gel (used when a non-organic gelling agent is required)

2. Chemically Defined vs. Chemically Complex Media

   • Chemically Defined Media
     • -The exact chemical composition is known Ex: minimal media used in bacterial genetics experiments
   • Chemically Complex Media
     • -The exact chemical composition is NOT known  -Often consist of plant or animal extracts, such as soybean meal, milk, protein, etc. -Include most routine laboratory media EX: tryptic soy broth

3. Selective Media

   • -Contain agents that inhibit the growth of certain bacteria while permitting the growth of others -Used to isolate specific organisms from a large population of contaminants

4. Differential Media

   • -Contain indicators that react differently with different organisms (for example, producing colonies with different colors) -Used to identify specific organisms

5. Pure Culture Technique

   • Streak Plate Method
     • -Developed in the 1870s by Koch & his co-workers -Objective: to obtain isolated colonies, spots of growth that come from a single parent cell -Method: streak the sample on semisolid medium, containing a gelling agent - Agar: the most commonly used gelling agent
   • Spread Plating & Pour Plating
   • Limiting Dilution