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Yellow E. coli colonies on MACCONKEY AGAR - (Apr/27/2009 )


Does anyone having idea that E.coli culture can give slight yellowish colonies on Macckonkey agar . I havent seen such type of colonies in past. Presently I am trying to demonstrate purity of one of the E. coli culture. All other test like Indole test is showing E. coli , but on Macconkey few colonies are yellowish. Does anyone has idea about this. Your suggestions and observations are necessary to come out with conclusion.



"Few of the colonies"? So not all? You sure it's a pure culture?


Our experience is that E.coli DH5α and NM522 cells are yellowish on MACCONKEY agar.

T :)

-Tanja N-