Task 4 A. Describe the differences between gram-positive and gram-negative cell walls. The difference is the outer casing of the bacteria. Gram positive cell wall consists of a smooth and thick wall. A gram positive bacteria will have a thick layer of peptidoglycan (a sugar-protein shell) that the stain can penetrate and teichoic acids. In this case the lactobacillus and staphylococcus are gram positive. A gram negative cell wall is wavy and much thinner and has a couple of layers of peptidoglycan. This is enclosed by an outer membrane made of phospholipids other substances. The outer membrane prevents the initial stain from penetrating. The Escherichia coli has a gram negative cell walls dye (Levinson, 2014). B. Explain what causes gram-negative bacteria to stain pink. Gram-negative bacteria are bacteria that do not retain the crystal violet dye in the Gram stain procedure. The crystal violet dye is washed by acetone and counter stain stick on its cell wall. The cells appear pink because of the color of the counterstain (safranin) (Levinson, 2014). In this case, it applied to the Escherichia coli bacteria since the thinner peptidoglycan layer in their cell wall did not allow for the stain to retain. C. Explain what causes gram-positive bacteria to stain purple. The iodine binds the crystal violet stain in the cell wall preventing counter stain from sticking onto the wall. The lactobacillus and staphylococcus bacteria which are gram positive bacteria’s stain purple as a result of the presence of a thick peptidoglycan layer in the walls of their cell. The gram positive thick wall prevents discoloration of the crystal violet dye (Levinson, 2014). D. Explain the purpose of iodine in the Gram stain procedure. Iodine acts as a