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In protocols for minimal media for growing bacteria I often see that a vitamin mix or a mix of various trace metals is added. But at least for E. coli I know that those are not strictly necessary, they also grow in minimal medium without any of this.

Does it make sense to add vitamins or trace elements when growing common E. coli for protein expression like BL21 (DE3) in minimal medium? Is there some literature data on how this can affect the growth of the bacteria?

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Not sure that I have ever come across trace metals in recipes (I assume that you aren't referring to the Ca/Mg salts component of M9), but it is certainly the case that many K12 strains (e.g. C600, DH5α) require thiamine because they are thi mutants. This doesn't apply to BL21 since it is from a different lineage (it is a B strain). In a lab where several strains are being used it will always make sense to standardise on a universal recipe so that the medium available will suit all strains in use.

There is a useful list of E.coli genotypes here.

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Adding trace elements (Fe, Co) and vitamins will increase the growth rate of E coli quite significantly.

However in the context of protein expression, more is sometimes not better. The proteins produced under high yield conditions may be miss-folded and non functional. The only way to know is to test it out.

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