Classification of Bacteria PPT

Classification / January 2, 2017

b. Enrichment culture medium
Enrichment medium is used to increase the relative concentration of certain microorganisms in the culture prior to plating on solid selective medium. Unlike selective media, enrichment culture is typically used as broth medium. Enrichment media are liquid media that also serves to inhibit commensals in the clinical specimen. S are used to recover pathogens from fecal specimens.

4. Differential/ indicator medium: differential appearance:
Certain media are designed in such a way that different bacteria can be recognized on the basis of their colony colour. Various approaches include incorporation of dyes, metabolic substrates etc, so that those bacteria that utilize them appear as differently coloured colonies. Such media are called differential media or indicator media. Differential media allow the growth of more than one microorganism of interest but with morphologically distinguishable colonies.
Examples of differential media include:

  1. Mannitol salts agar (mannitol fermentation = yellow)
  2. Blood agar (various kinds of hemolysis i.e. α, β and γ hemolysis)
  3. (lactose fermenters, pink colonies whereas non- lactose fermenter produces pale or colorless colonies.
  4. (Vibrio cholerae produces yellow colonies due to fermentation of sucrose)