The goals for this medium were to find a convenient and well defined composition that allowed varying all of the elements independently to facilitate isotopic labelling. This required using much less phosphate than in older media, which served roles of pH buffering and chelation of metals like Fe2+. For buffering, MOPS was used instead, with some Tricine added to help chelate Fe2+.
E. coli can use MOPS as a sulfur source if not other sulfur source is added. However, sulfate easily outcompetes MOPS if both are present.
To increase ionic strength and thus optimize the growth rate, NaCl was added. However, it is probably the case that KCl would work just as well, which would allow completely eliminating Na+ from this medium.
| Recipe Substances:
Osmolarity (approximate, computed from constituents): 0.31 Osm/L
Wildtype growth observations:
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