Student’s Name: Instructor’s Name: Course Number: Date: UNKNOWN IDENTIFICATION LABORATORY REPORT Introduction The Gram Stain test: This is a very important preliminary test used in initial classification as well as characterization of bacteria. It is used to differentiate bacteria based on staining differences in biochemical and physical characteristics of bacterial cell walls. The Gram Stain test therefore groups bacteria into two major categories: Gram-positive and Gram-negative bacteria. Not only is the test important in distinguishing between the two classes of bacteria, but also helpful in staining the bacteria for clear observation of their morphology under a light microscope. Gram-positive bacteria are identified by the purple color retention after the staining procedure while the Gram-negative bacteria give pink coloration on their cell walls. The differences in color retention are attributed to difference in physical and chemical composition in their cell walls. For example, the Gram-positive have a relatively thick cell wall composed of 90% peptidoglycan complex and teichoic acid cross-links. On the contrary, Gram-negative bacteria have thin cell walls composed of only 10% peptidoglycan complex and high lipid content. The thick cell walls in Gram-positive bacteria make them retain the purple color of crystal violet dye, even after being treated with ethanol. However, the crystal violet dye is quickly decolorized by ethanol, and they on...