Genus: Escherichia (on EMB agar)

Escherichia coli ( E.coli )

Medium: EMB (Eosin Methylene Blue) agar
Source: Fecal sample
Gram reaction: Gram negative
Morphology: Rod

• EMB is both selective and differential media
  
• EMB contains eosin and methylene blue dyes which inhibit the growth of gram-positive bacteria and therefore support (select) the growth of gram-negative bacteria
• EMB also contains lactose, which differentiate non-enteric bacteria based on thier ability to ferment lactose

Results:
Lactose fermenting bacteria yield colored colonies

• E.coli colonies appear blue black with green metallic sheen when viewed with reflected light indicating fermentation of lactose and acid production which precipitates the green metallic pigment.
  

Non-lactose fermenters will yield colorless colonies such as Pseudomonas and Proteus

Pseudomonas