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What are some examples of selective and differential media?
Posted December 22, 2023

Answer

Examples of selective media include: eosin methylene blue, MacConkey agar, Terrific Broth, YM (yeast and mold), hektoen enteric agar, xylose lysine, and Mannitol salt agar. 

  • Eosin methylene blue inhibits Gram-positive bacteria due to the presence of methylene blue, permitting only the growth of Gram-negative bacteria. 
  • YM has a low pH, hampering the growth of bacteria. 
  • Xylose lysine is selective for Gram-negative bacteria. 
  • Mannitol salt agar encourages the growth of Gram-positive bacteria and is distinctive for mannitol. 
  • Terrific Broth with glycerol is used specifically for growing recombinant strains of E. coli.
  • Hektoen enteric agar is designed for Gram-negative bacteria.

Examples of differential media include: blood agar, X-gal plates, Streptococcuseosin methylene blue, and MacConkey agar. 

  • Blood agar contains bovine heart blood which becomes see-through when hemolytic activity occurs. 
  • X-gal plates are used to identify lac operon mutants.
  • MacConkey agar helps differentiate bacteria based on their capacity for lactose fermentation. 
  • Streptococcuseosin methylene blue distinguishes bacteria based on its ability to ferment lactose and sucrose.