What happens when the pH indicator is left out of macConkey agar?

Answer 1

If the pH indicator is left out of MacConkey agar, the medium will lose its ability to indicate lactose fermentation visually. Normally, the pH indicator (neutral red) changes color in response to acid production from lactose fermentation, allowing for the differentiation of lactose-positive bacteria, which turn pink, from lactose-negative bacteria, which remain colorless. Without the indicator, it becomes difficult to distinguish between these bacterial groups, compromising the effectiveness of the medium for selective isolation and identification.