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Home Q & A Board Biology-Related Homework Help Cell Biology
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smoran1 smoran1
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11 years ago
A student completed the Gram stain technique, but neglected to use the Gram?s Iodine.  What effect would this have on a Gram-positive bacterium?  What effect would this have on a Gram-negative bacterium?  And why for both bacteria?
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#1
11 years ago
In both, the crystal violet will not be attached to the cell wall.  The Gram-positives will destain and give an inaccurate result.  The improper staining will not impact the Gram-negative outcome.
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#2
Educator
8 years ago
Gram’s iodine acts as an astringent causing the crystal violet dye to penetrate and stain gram-positive organisms. The gram-positive organisms will not be decolourized as easily as gram-negative organisms by an acetone-alcohol. Safranin is added as a “counter stain” which stains all non-gram-positive organisms a pink/red colour. If Gram’s iodine is not used in this process, the gram-positive organisms will not show up violet, they will instead show up a pink/red colour (Gram’s stain, 2003). 
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