The key differential step in the Gram stain is: Group of answer choices none is considered differential the application of crystal violet the application of the iodine mordant application of safranin red dye the alcohol wash step

To determine the key differential step in the Gram stain, let's analyze each option:

1. None is considered differential: This option suggests that no step in the Gram stain process is differential, which is incorrect because the Gram stain is specifically designed to differentiate between Gram-positive and Gram-negative bacteria.

2. The application of crystal violet: This is the primary stain that colors all the cells purple initially, but it is not the differential step because it does not distinguish between different types of bacteria.

3. The application of the iodine mordant: Iodine acts as a mordant, forming a complex with crystal violet, which helps to fix the dye in the cell wall. However, this step alone does not differentiate between Gram-positive and Gram-negative bacteria.

4. Application of safranin red dye: Safranin is the counterstain that colors Gram-negative bacteria pink/red after the decolorization step. While important, it is not the key differential step.

5. The alcohol wash step: This is the critical differential step. The alcohol (or acetone-alcohol) wash decolorizes Gram-negative bacteria by dissolving the outer membrane and allowing the crystal violet-iodine complex to be washed out, while Gram-positive bacteria retain the complex due to their thicker peptidoglycan layer.

Therefore, the correct answer is:

The alcohol wash step