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Gram Stain

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Gram Stain

Postby adam00f » Tue May 17, 2005 2:51 am

Im studying for my State Bio testing final and im confused in Gram stain tesing. Crooect me if im wrong.

-Positive For present bactria have a Violet stain witch means that the bacteria has a cell wall.

-Negetive means that the bacteria loose the violet color anda cell wall is not a charataristic of the bacteria..

please crooect me or give me more info..
Summer schedual/ gotta cram all chemo info and i have water polo practice 3 tiomes a day!!!!!!!..frick i nned some sleep!!
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Postby muntedkowhai » Tue May 17, 2005 6:05 am

gram positive bacteria have a lot of Peptidoglycan layer. dont put cell walls.
gram positives are violet because the PG layer holds on to the stain.

Gram negatives are pink because unlike positives, they do not have a thick layer of PG, but rather, lipid membranes. since they dont have pg layers, they dont hold the crystal violet and it gets washed by the gram stainning steps.
the alcohol punches holes in the lipids and allows safarin to sip in and stain thebacteria.
and hence gram negatives are pink.

you have to be careful not to use cell walls but to remember it is the peptidoglycan layer that is significant in stainning of gram negative and positives.

i suggest you read deeper into the chemical and true interactions of the stains and structures of the bacterial membranes to get a better idea.
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Postby biostudent84 » Tue May 17, 2005 6:30 am

Gram positive showing violet can also mean that there are two lipid bilayer for a cell membrane.

Grap negative showing pink can also mean that there has only one lipid bilayer for a cell membrane.
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Postby adam00f » Wed May 18, 2005 2:41 am

Thanks guys

^_^
Summer schedual/ gotta cram all chemo info and i have water polo practice 3 tiomes a day!!!!!!!..frick i nned some sleep!!
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Postby b_d_41501 » Tue May 31, 2005 11:31 pm

I had a little device to learn the colors: Gram Positive = Purple & Gram Negative = Nipple (hence the pink color) lol. Hey it worked for me!! If the gram stain results in the primary stain (crystal violet) being retained then it is +. If the gram stain results in the primary stain being decolorized and the counterstain (safranin) being retained, then it is -.
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