Exam (elaborations) Microbiology_task_2021

Introduction: Gram-positive and Gram-negative bacteria have a big difference in cell wall structure that is examined during the gram staining lab. Gram-positive bacteria have thick layers of peptidoglycan. When these bacteria are stained, using a crystal violet dye, they will remain purple. Gram-negative bacteria have thin peptidoglycan walls, which do not retain the purple dye. It must be counterstained with safranin turning them pink. Materials and Methods: There are four basic steps for gram staining. The first step is to flood the cells with crystal violet dye for 1 minute and then rinse. Step 2 is to put iodine on the cells so that the violet dye sticks more. Step 3 is to decolorize with alcohol to dissolve the cell membrane and then rinse with water. This step determines if the cells are positive or negative. If they are positive, the cells will remain purple, if they are negative, they will be clear. The final step is to counterstain with safranin for 30-60 seconds, then rinse with water and dry. The gram-negative cells will turn pink and the positive will stay purple.