SOB/SOC: Super Optimal Broth

For SOB:

200mL	250mL	1L	Final [ ]	Component
1 g	1.25 g	5 g	0.5%	yeast extract
4 g	5 g	20 g	2.0%	tryptone
0.12 g	0.125 g	0.5 g	10 mM	NaCl
0.037 g*	0.042 g*	0.186 g	2 mM	KCl
0.48 g	0.6 g	2.4 g	20 mM	MgSO4 (anhydrous)

*Don't measure; it's just a pinch.

Adjust to pH 7.5 with 1M NaOH.

Note: 200 ml of SOC makes 25 vials of 8 ml each.

For 1 L: Add 800 ml of dH₂O and dissolve components. Adjust to pH 7.5 prior to use with 1 M NaOH (approximately 25 ml). Add dH₂O to a final volume 1 L.

Autoclave.

For SOC (=SOB+glucose)

Bulk scale: Make SOB, except add dH₂O to a final volume of 960 ml instead of 1 L. Autoclave. When solution has cooled to 50°C (cool enough to touch with bare hands for a few seconds), add 40 ml of sterile 10% (w/v) glucose. (That's a final concentration of 0.4% glucose or about 20 mM.)

Smaller scale: To achieve a 20 mM concentration of glucose for a known final volume n of SOC, you can calculate the amount of 10% w/v glucose to be added as 0.036n. The amount of SOB to add is then 0.964n. Keep units constant, so if n is in µL, the final amounts will also be in µL and so on.

• Note: If you have a known volume of SOB x and want to know how much 10% w/v glucose to add to make SOC containing 20 mM glucose, simply divide x/0.964 to get your final volume n and subtract x from n to get the volume of 10% w/v glucose to add.

Generally when making stocks of SOC it is advisable to make smaller volume aliquots rather than larger ones. SOC media is extremely rich and can contaminate easily particularly after glucose is added. Additionally, smaller volumes tend to be pulled from it repeatedly with pipettes, which increases the chances of contamination over time.

Note: Some recipes for SOB use 10 mM MgSO₄ and 10 mM MgCl.