Common Microbiological Media for Aerobic Cultures

Most aerobic species of bacteria (those that can grow in the ambient 20% O2 found in earth's atmosphere), will grow on one or more of the media types below.

Solid media commonly contain 1.5% agar per weight to solidify the liquid, nutrient part of the media. After sterilization, the liquid media is poured into sterile Petrie plates - think of it along the lines of pouring heated jellow into small cylindrical molds.. Petrie plates are commonly made of plastic, and can be purchased already sterlilzed with 25 or more per package.

Luria Bertani Broth (LB)
MacConkey Agar
Sheep's Blood Agar
Chocolate Agar
Hektoen Enteric Agar
LB broth LB agar
MacConkey Agar
5% Sheep's Blood Agar
Chocolate Agar
Hektoen Enteric Agar
Uses: Culture of aerobic bacterial species
Uses: Culture of aerobic bacterial species on solid media
Uses: Selective media for Gram-negative, enteric bacteria (bile tolerant). Assess lactose fermentation
Uses: Non-selective media, good for culturing many bacterial species including Gram negative and Gram-positive species including Staphylococci and Streptococci
Uses: Very enriched media with lysed red cells, to release many nutrients needed by *fastidious* organisms.

It may look like chocolate, but would have a rather nasty flavor, like coagulated blood-flavored jello..
Uses: Selective media for Gram-negative enteric bacteria (higher bile salt concentrations than MacConkey).

Used to assess lactose fermentation AND ability to produce hydrogen sulfide (H2S). Allows for distinguishing among, E. coli, Salmonella and other gut pathogens including Shigella species
  • 10g Tryptone
  • 5g Yeast Extract
  • 10g NaCl
  • 1L distilled water
pH to ~7.3-7.5.
Distribute 5-10mL into glass tubes with autoclavable tops.

Autoclave 30 minutes, OR place in a pressure cooker for ~45 minutes @ 15 pounds pressure.

Same as for LB-broth, but add 15g of agar prior to autoclaving.

Be certain to mix thoroughly prior to pouring media into Petrie plates.
  • 10g lactose
  • 20g peptone
  • 5g bile salts
  • "pinch" or small amount of 1mg/mL Bromcresol purple or Crystal violet solution.
  • 15g agar
  • 1L distilled water
  • 5% anticoagulated Sheep's blood
  • Tryptose Soy nutrient agar base (contains agar in it).
  • 1L of water
Recipe: Recommend commerically produced media.
Recipe: Recommend commercially produced media.

If bought in powder form, must heat over heating plate prior to pouring plates. Do not autoclave.