Lidstrom:E. coli media comparison

common medias

LB

• A default rich media for E. coli
• LB contains a milk digest (tryptone) and hence can induce cultures with lac based promoters when they near saturation.
  • "LB ... contains enzymatic digests of the milk protein casein (e.g., tryptone or N-Z-amine) and yeast extract. Since milk is rich in lactose, an inducer of the T7 expression system, variable amounts of residual lactose may be present in different lots of these enzymatic digests. These small amounts of lactose do not promote appreciable induction during log-phase growth, but even minute amounts are sufficient to cause induction on approach to saturation, particularly at lower rates of aeration, which allow induction at lower lactose concentration and promote higher levels of induction." -- Sturdier 2014
• This article criticizes LB for its low magnesium and carbohydrate content, and is a must-read for understanding rich media options.

NB

• Stands for "nutrient broth"
• Lower in salt (NaCl) than LB

SOB

• "SOB" = "super optimal broth"
• similar to LB, but contains Mg2+ and has 1/20th the salt. Sterile Mg is added after autoclaving the rest.

"' SOC "'

• SOC = SOB + glucose. "C" stands for catabolite and is jargon for glucose in this case. The glucose is added after autoclaving as well.

Autoinduction (Sturdier)

• It is called auto-induction because it causes lac-based expression as cultures near saturation. No addition of IPTG is required.
• See: Lidstrom:Autoinduction_Media

M9

• Minimal (no yeast extract or milk digest)

Media tips

• You can autoclave sugars by themselves. Discard if they come out discolored.
  • People usually don't autoclave mixtures with sugars added. Sterilized sugars are usually added afterward.
  • Autoclaving can change the solution volume, affecting any calculations you did for the stock concentration.
  • Usually you lose a little liquid volume in the autoclave. This is another reason really precise recipes often call for filtered sugar solutions.

• Don't autoclave Na or K phosphate salts in the presence of other stuff
  • It can cause precipitation of metals and stuff.

What solutions can/can't I autoclave?

• Doesn’t Play Well with Others- The Chemistry of the Autoclave discusses why glucose is often filtered instead of autoclaved.
  • phosphate tends to precipitate ionic metals in a temperature and pH dependent manner.
  • sugar + phosphate --> carmelization