Final answer:
Shigella will appear colorless or white on MacConkey Agar and EMB Agar because it is a non-lactose fermenter. On Nutrient Agar, which does not differentiate lactose fermentation, Shigella will simply grow without any particular color change. On XLD Agar, Shigella will display colonies with a color indicative of non-lactose fermentation. The correct option is 1.Nutrient Agar
Step-by-step explanation:
When determining the color that Shigella will appear on various agar plates, we must consider if it is capable of fermenting lactose. On a MacConkey Agar plate, Gram-negative lactose fermenters produce pink or red colonies due to their ability to ferment lactose, which leads to acid production and a color change in the pH indicator. Since Shigella is a non-lactose fermenter, its colonies will appear colorless or white on the MacConkey Agar.
Similarly, EMB Agar contains indicators that differentiate based on lactose fermentation. Lactose fermenters display metallic-green or deep purple colonies, but Shigella, as a non-fermenter, will produce colorless colonies. On Nutrient Agar, which is not differential, Shigella would just grow without a color change.
Lastly, on XLD Agar, which also differentiates lactose fermenters from non-fermenters, Shigella would likely produce colonies with a color indicative of non-fermentation, which is typically red due to the presence of other fermentation pathways specific to Shigella that affect the pH indicator in the medium. The correct option is 1.Nutrient Agar