Figure 2.4 Step 1 Flood the heat-fixed smear with crystal Result: violet for 1 min All cells purple Step 2 Add iodine solution for 1 min Result: All cells remain purple Step 3 Decolorize with alcohol briefly Result: 一about20sec Gram-positive cells are purple; gram-negative cells are colorless Step4 Counterstain with Result: safranin for 1-2 min Gram-positive (G)cells are purple; gram-negative(G-)cells are pink to red (a) FLASH (c)Figure 2.4 Step 1 Step 2 Step 3 Step 4 Result: All cells purple Result: All cells remain purple Result: Gram -positive cells are purple; gram -negative cells are colorless Result: Gram -positive (G + ) cells are purple; gram -negative (G - ) cells are pink to red Flood the heat -fixed smear with crystal violet for 1 min Add iodine solution for 1 min Decolorize with alcohol briefly — about 20 sec Counterstain with safranin for 1 –2 min G + G - Leon J. Lebeau Molecular Porobes, Inc., Eugene, Oregon FLASH