Question

With respect to MacConkey agar, what would be thepossible consequence of

a) replacing the lactose with glucose? Would you be able to distinguish E.coli from PV if there is glucose instead?
b) replacing the neutral red with phenol red (yellow when acidic, red or pink when alkaline)

Answer 1

a) If lactose is replaced with glucose in MacConkey agar, it would no longer be possible to differentiate E.coli from other members of the Enterobacteriaceae family.

b) If neutral red is replaced with phenol red in MacConkey agar, the medium can still differentiate lactose-fermenting bacteria from non-lactose fermenting bacteria, but the color change would be different.