Micro Help

trin

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11 years ago

Micro Help

What would happen if you forgot to counterstain with safranin?
Answer

   G- would appear light purple/blue.

   Would not be able to see any bacteria.

   Would not be able to see any G- bacteria.

   Would not be able to see any G+ bacteria.

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jay_rob

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11 years ago

If the organism is Gram positive, it means that the crystal violet reacted with the iodine to form a complex that was trapped in the large peptidoglycan layer found in these cells. As a result, would these cells appear the same if you forgot the safranin step during the Gram Stain process? Yes. The safranin is a light pink/red color which is overshadowed by the purple primary stain. So these Gram positive cells would still appear the same purple color.

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trin Author

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11 years ago

So A?

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duddy

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11 years ago

If you don't counterstain with safranin, it will be difficult to visualize and identify of Gram-negative bacteria, and their thin cell walls may have bound enough crystal violet that they will be misidentified as Gram-positive.

I'm going with Rightwards Arrow

Would not be able to see any G- bacteria.

Update us when you have a chance.

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trin Author

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11 years ago

I just reopened it up. I did get that one right. It was the one below it I got wrong! ooops

What is happening during the decolorization step?
Answer

   Alcohol binds to crystal violet in bacteria and inactivates it.

   Alcohol disrupts membrane proteins and allows cell membrane and peptidoglycan to become leaky.

   Alcohol destroys crystal violet-iodine complex.

   Alcohol locks in safranin counterstain.

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how_mendel

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11 years ago

Quote from: trin (11 years ago)

Alcohol disrupts membrane proteins and allows cell membrane and peptidoglycan to become leaky.

When a decolorizer such as alcohol or acetone is added, it interacts with the lipids of the cell membrane. A Gram-negative cell will lose its outer lipopolysaccharide membrane, and the inner peptidoglycan layer is left exposed.

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