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Gram Staining: A. Add crystal violet stain over the fixed culture. Let stand for 10 to 60 seconds; for thinly prepared slides, it is usually acceptable to pour the stain on and off immediately. Pour off the stain and gently rinse the excess stain with a stream of water from a faucet or a plastic water bottle. Note that the objective of this step is to wash off the stain, not the fixed culture. B. Add the iodine solution on the smear, enough to cover the fixed culture. Let stand for 10 to 60 seconds.
Gram positive and gram negative is one way of classifying a bacteria. Gram positive bacterias have a cell wall which will stain in violet color. Gram negative bacterias, how â¦ ever, have an extra layer of cell wall around them which prevents the cell wall from being dyed.acteria can have two types of cell walls. Gram-Po â¦ sitive bacteria have a relatively thick layer of peptidoglycan. Gram-negative bacteria have a much thinner layer of peptidoglycan. There are 4 basic steps to a Gram-staining.