When we stain the cell with our purple dye, the thick layer of Peptidoglycan prevents the purple stain from leaking out back into our surroundings when we wash those bacterial cells with water. So under the microscope, Grampositive bacterial cells appear purple. Now, in both types of these cells, the periplasmic space, as I mentioned earlier, basically contains important hydrolytic enzymes that break down different types of molecules that are then ingested into the cell so that the cell can use them to basically function properly. Now, let's move on to the Gram negative bacteria. So the main difference between Gram positive and Gram negative is the thickness of our cell wall of that Peptidoglycan layer. So these bacterial cells are characterized by a thin Peptidoglycan cell wall.