Fermentative growth medium: Mc Conkey

lamb L.A.M.Buisman at cable.A2000.nl
Sat Jan 23 09:19:45 EST 1999

Or fermentation of other carbohydrates.
Pink, red, colourless because of pH, not pigment.
In case of red Serratia it is the red pigment.

Bob/Judy Dilworth wrote:

> MacConkey agar is for the differentiation of lactose fermenters.  Lac+
> colonies are purple (E. coli) or pink (Klebsiella/Enterobacter gp.) while
> Lac - colonies are colorless (Proteus sp., Providencia, Serratia, and many
> others).  The red strains of Serratia marcescens can look reddish on this
> medium, but it is a different color than the Lac + bacteria.  Hope this
> helps.
> Judy Dilworth, M.T. (ASCP)
> Microbiology
> Luis Fernando Garcia Alles wrote:
> > Dear all,
> > hi! Just to jog my rotting memory, does anyone there remember how
> > exactly the Mc Conkey test of colonies turning pink if they ferment the
> > substrate sugar is supposed to work? Is the colour yellow/red to be
> > obsered arounfd the cells or in the colonies? Do the cells take up the
> > pigments? How?
> > Any one of these qustions answered would be a great help.
> > Cheers.
> > Chaitanya.

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