2. What color would a Gram-negative cell be if we skipped the alcohol step? What color would a Gram-positive cell be if we skipped the same step? Why?

Answer 1

First thing to do is to know why the alcohol step is used. Ethyl alcohol, or acetone, is used as a decolorizer. On the macromolecular level, this means the petpidoglycan is "shrunk". In Gram Positive bacteria, this tighter peptidoglycan layer prevents the the complex of crystal violet dye and iodine from escaping the cell. In Gram Negative bacteria, the outer membrane is degraded and thin, shrunk peptidoglycan layer is unable to keep the complex inside the cell.

Now to answer the question. In Gram positive bacteria, since the crystal violet-iodide complex was not "trapped" by the alcohol in the cell, it will be stained red by the safranin. However, because the violet-iodide is relatively brighter than the safranin and its escape from the cell could be slowed down by the peptidoglycan layer , I would assume that there would be some bacteria with a slight purple stain, though not 100% of them.

For the Gram-negative bacteria, they will simply be stained red by the safranin.