MacConkey agar results

Cory Bystrom cbystrom at darkwing.uoregon.edu
Wed Apr 10 11:46:24 EST 1996


I've been trying to find an answer regarding some characteristics of
bacteria that grow on MacConkeys agar.  Microbiology texts haven't been
much help and I'd like to hear some opinions.

I've prepared two mutants of a sugar kinase and added the respective sugar
to the agar to select for the correct clones.  When I sequence each of the
clones picked from the MacConkeys agar I confirm that they both carry the
mutation.  However, the color of the colonies from the two mutants is
strikingly different.  One gives the classic deep red colonies with bile
precipitate under overgrown areas.  The second gives weakly pink colonies
and the agar slowly becomes yellow after two days of incubation. I expect
that both of these mutations to have no effect on the activity of the
kinase that I've mutated.

This being said, is it possible that the mutations *have* changed the
activity of the kinase and that this is reflected in the ability for the
bacteria to ferment the selected sugar?  Is it possible that the level of
expression is different?

I'd really appreciate any insight that anyone has on this.


‚ory Bystrom
University of Oregon

More information about the Microbio mailing list

Send comments to us at biosci-help [At] net.bio.net