Microbiology: A Systems Approach 4th Edition by Marjorie Kelly Cowan

Exercise 13

From chapter 3, figure 3.5 b. What biochemical characteristic does this figure illustrate How could this characteristic be used to begin the identification of these organisms Explain your answer.
Figure 3.5 Examples of media that are both selective and differential.
(b) MacConkey agar selects against gram-positive bacteria. It also differentiates between lactose-fermenting bacteria (indicated by a pink-red reaction in the center of the colony) and lactose-negative bacteria (indicated by an off-white colony with no dye reaction).