whatis the difference between selective and differential media?

Answer 1

Wikipedia explains it nicely:

"Differential media are used to distinguish one microorganism type from another growing on the same media. While selective media are used to allow the growth of only select microoganisms, differential media allow the growth of multiple types, but result in distinguishing characteristics (such as the production of a brightly coloured or phosphorescent dye). Growth media can be both selective and differential".


For example
Imagine that you have E.coli and you tranform with a plasmid that gives ampicillin resistance and expresses lacZ when induced with IPTG and only if you haven't cloned anything into the plasmid. If you grow the cells on a plate with medium+ampicillin then you are selecting, ie allowing only cells which have the plasmid to grow. If you also add IPTG and X-Gal the colonies that have a plasmid with a clone will be white, while the ones that carry the parental plasmid will be blue. In this case you have both selective (because of the ampicillin) and differential (because of IPTG and X-gal) medium.

Answer 2

Selective media allows only for the growth of organisms with the marker that you select for. For example if you transform a gene of interest into bacteria you also transform in a marker (eg. resistance against ampicillin) so you can select for those organisms that received your gene.
Differential media allows for growth of different kind of organisms with different morphologies (eg. blood agar)

Answer 3

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