Question

You have made a smear of a bacterial culture and have performed the Gram stain on it. Looking at the organism under the microscope, you notice that the cells do not seem to be the dark blue-purple of a gram-positive reaction, but instead are light blue. Your staining procedure was performed correctly. What is your best explanation as to why the bacteria have stained this way?A.forgetting to heat fix the smear B.skipping the iodine step C.skipping alcohol steps D.skipping the Safranin step E. skipping the crystal violet step

Answer 1

If we have to think quickly about the function of each component we would say that:

-fixing the semar is for adhesion to slide glass

-lugol will fix the violet crystal dye to bacteria

-alcohol eliminate the violet crystal from gram negative ones

-safranin, will stain the gram negatives which are the ones that are discolored

So if your preparation is clearer than usual I would think in:

Option B skipping the iodine step therefore there would be no intensification in crystal violet (this could be the best explanation).

Option A forgetting to heat fix the smear, this is a previous and fundamental step that makes adhesion to slide glass. If you skip it, probably your preparation could be clearer than usual since the bacteria did not fix correctly to the glass.