MBS (Modified Barth’s Saline)


for 4 liters of 3X Final Concentration
4 M NaCl 264 ml (or 61.7 g dry) 88.0 mM
1 M MgSO4 9.84 ml 0.82 mM
0.8 M NaHCO3 36 ml (or 2.42 g dry) 2.4 mM
1 M KCl 12 ml 1.0 mM
1 M Ca(NO3)2 3.96 ml 0.33 mM
1 M CaCl2 4.92 ml 0.41 mM
Hepes (e.g. Sigma H3375) 28.6 g 10 mM

Adjust to pH 7.4 w/ 10N NaOH

Add 2.22 ml of Phenol Red (Sigma P0290) to 4 liters of 3X

All solutions, as well as dilution to culture strength (1/3 X) should be made with nanopure or molecular biology grade “box” water (e.g. Thermo Scientific 23751628)

Stock solutions are kept at 4C (we don’t autoclave them)

Final product should be filter sterilized into an autoclaved embryological bottle

We routinely make 3X stock (10X MBS does not hold pH on dilution); keeps at 4C indefinitely

(Updated:  4/26/10 by David Shook; original source: Gurdon, 1977  Methods in Cell Biology 16:125-139, minus antibiotics/antimycotics)