LABORATORY REPORT Gram Staining PURPOSE The Purpose of Gram Staining is for identifying and clasifying bacteria for example Grom stain enables to bacteria as either gram Positive or gram negalive EXPECTED RESULTS red 1 What color will a gram negative cell stain red 2 What color will a grand Positive cell stain Purple 3 Which organism used in this exercise is a coccus Staphylococus epilkimis RESULTS Sketch a few bacteria viewed with the oil immersion objective lens gram negative Bacterium Total magnification Color Morphology and arrangement Short Gram reaction Staphylococcus epidermidis 1000 x Cocci red Negative Bacillus subtilis gram Positive Escherichia coli 1000x bacili Purple Positive 2 Did your results agree with the infor yes my results agree with the information QUESTIONS 1 Why do gram positive cells more than 24 hours old stain gram negative It is because Wall begins to degenerate af 24 hours 2 Can iodine be added before the primary stain in a Gram stain No It should not be added in because it s a Fixativeagent Crystal 3 List the steps of the Gram staining procedure in order omit washings and fill in the color of gram positive cells and gram negative cells after each step Step 1 2 3 4 Chemical Primary tain Cryskil videt Mordant Grams lodine Decolourizer Ethyl Alcohol Secondary Stain Gram Positive Cells Purple Purple Purple Purple the Appearance Gram Negative Cells Purple Purple Colorless 4 Which step can you omit without affecting determination of the Gram reaction Any step can be omitted All the steps play an important role too Prevent contamination CRITICAL THINKING 1 Suppose you performed a Gram stain on a sample from a pure culture of bacteria and observed a field of red and purple cocci Adjacent cells were not always the same color What would you conclude 2 Suppose you are viewing a Gram stained field of red rods and purple cocci through the microscope What do you conclude