Reinforced Clostridial Medium

Description

Reinforced Clostridial Medium (RCM) is a common rich undefined microbiological medium for the anaerobic culturing of microbes.

Recipe

Compound	g/L
Yeast Extract	13
Peptone	10
Soluble Starch	1
Glucose	5
Cysteine HCl	0.5
Sodium Chloride	5
Sodium Acetate	3
Agar	0.5

Note: some suppliers may replace up to 10 g of yeast extract with meat extract

Directions

Suspend 38 g of RCM in 1 liter of distilled water. Boil to dissolve solids completely, aliquot, and sterilize by autoclaving at 121 °C for 15 minutes.

Notes

Cell pellet of Megasphaera elsdenii strain AG22635 after a 10-minute 5000 x g centrifuge spin. The culture on the left was grown in commercial RCM. The culture on the right was grown in lab-made RCM without agar.

Store bought RCM contains 0.5 g/L agar to mitigate oxygen permeability into the medium. The addition of this agar can have a compounding effect on the formation of extracellular polymeric substances (EPS) in some species like Sharpea azubuensis and Megasphaera elsdeni. This EPS generation makes the formation of cell pellets difficult and can affect the procedure of making competent cells. It's recommended to make your RCM "in house" without agar to avoid this complication.

Sources

• ThermoFisher CM0149 (Used by Guss Lab)